TPG 47.4.5 · 36,111 words · 2.7 hr read · Great Chatting Again

Cataloging Voting (part 5 of 7)

In addition to temporary alteration through desensitization, we know that arousal pathways can be altered (though not reliably) through shifts in a person’s hormones. When people go through hormone therapy during sex reassignment surgery, their sexuality goes through drastic changes (though we want to emphasize that being trans doesn’t really have anything to do with sexuality, only your gender identity—all we are saying is that changing your hormones can change what arouses you). Multiple studies show that around 40% of individuals report experiencing changes in their sexual attractions during transition. Statistically speaking, most of these changes include shifts from exclusive attraction to one gender pre-transition toward some level of attraction to both men and women post-transition, but around 13% of trans women switch from exclusive or primary attraction to women to exclusive or primary attraction to men (most research on transitions finds no such drastic changes among those who were initially attracted to men). Of trans men initially attracted exclusively to either men or women, 6-7% experienced a complete attraction reversal after transition.

That said, if you read many personal accounts of transitions, you will notice an interesting pattern: Something about our hormones is tied strongly to the aversion system we noted above, as many find stimuli that formerly generated a strong aversive impulse to suddenly be arousing. In other words, occasionally during a person’s hormonal transition, something they found to be icky before will suddenly and inexplicably start to arouse them, meaning the pathway that causes this flip is almost certainly using hormonal cues.

The Human Mating Season

Humans seem to have something of a mating season, which is weird because no one ever talks about it. This season lasts from Christmas through Valentine’s Day and reaches its peak on the Sunday after New Year’s Day (which in the dating industry is called Dating Sunday). This increase in dating activity can be seen very clearly in data from dating apps; however, seasonal fluctuations in dating behavior are not just a dating app phenomenon. There is actually a seasonal increase in sexual interest and desire over the same period. You will see an increase in Google searches for pornography and prostitution over this period. (We would love to conduct more research to determine whether this is a cross-cultural phenomenon and whether or not it affects genders differently.)

Writing on Eggshells—Human Sexual Dimorphism

There are dozens of manners in which we might offend any myriad of groups when writing on the topic of sexuality. Seeing as there is no means by which we can accommodate all (often opposing) groups, we are already bracing ourselves for the blowback. While we enthusiastically engage with the type of information that leads people to feel the type of offense humans generate when their beliefs about the world are credibly challenged, we go out of our way to avoid the type of offense generated from undermining an individual’s self-image (such offense serves no purpose outside of cruelty). Alas, avoiding such unintended personal attacks when discussing sexuality has us walking—er, writing—on eggshells.

For the most part, this eggshell stroll is just that: A delicate and pained walk over terminology. For example, we sometimes found ourselves racking our brains to determine whether to use the word sex or gender when talking about attraction to dimorphic traits in an evolutionary context, as evolution uses gender as a proxy for sex (e.g., hip sway is both a performative aspect of gender and a result of a sexually dimorphic female hip bone). Fortunately, when it comes to issues of semantics, there usually is a way to avoid offense—this is not the case with potentially offensive facts.

There is one political hot-button issue that we cannot dance around if we are to adequately delve into underlying mechanics driving sexual arousal and behavior: Humans are a sexually dimorphic species; this dimorphism extends to our arousal systems and behavioral impulses. In other words, males and females exhibit varying characteristics beyond just different sexual organs, and these variances extend to our behavioral impulses and arousal/aversion systems. The existence of sexual dimorphism is highly offensive to certain groups that wish to believe that there are zero cognitively ingrained differences between males and females.[[13]](#_ftn13) Some of these groups go so far as to argue that socialization is the only reason why women are more aroused by penises (on average) than males. (As you can imagine, it is very difficult to write a book on arousal patterns that does not break down on male-female differences in those patterns, hence our obligation to address this point.)

Men and women in the human species exhibit sexual dimorphism in almost every organ we have—from our digestive systems to our skin, dentition, and bones. The idea that evolution placed a magical “brain barrier” on sexual dimorphism is ludicrous, considering that homo sapiens would have had to somehow reverse the mental differences that clearly exist in our recent ape ancestors.

Our recent ancestors absolutely exhibit mental differences across sexes. If you put a bunch of chimps together with no previous chimp socialization, they almost always sort into a patriarchy, whereas bonobos almost always sort into a matriarchy (some have argued that sexually dimorphic behavioral patterns in chimpanzees were socialized through chimpanzees watching humans, but if this were true, we would have seen a similar effect in bonobos—and this effect is not seen). Heck, not just our most recent ancestors, but almost every well-studied social mammal species we can think of presents clear, sexually dimorphic behavior patterns that are not socialized.

When we assert that there are systematic statistical differences in male and female brains, and when we state that there are sexually dimorphic behavioral impulses which are not socialized, we are not claiming that there are “male brains” and “female brains.” One cannot look at a brain and tell if its owner is male or female. Asserting that a person who claims there are statistical differences in behavior patterns is arguing for biological determinism is akin to saying that a person stating that men and women have different heights on average is basically saying there is a “male height” and a “female height” and that by measuring a person’s height you can tell their sex.

We also do not claim that socialization plays no role in male and female differences. Socialization plays a huge role in male and female behavioral patterns; it simply is not the only influence at play.

To our great consternation, individuals who deny sexual dimorphism of behavioral patterns will often admit that men and women have different aggregate rates of certain hormones, and that those hormones impact behavior. They admit this because:

1. It is easily and objectively testable that men have more testosterone than women on average.
2. Even a street junky knows when you shoot up roids your behavior will change. (“Roids” are the street name of anabolic steroids, which include testosterone and testosterone precursors.)

While some of the specific effects claimed to be associated with testosterone or estrogen can be credibly challenged (such as the claim that testosterone leads to more risk-taking behavior), it is absurd to claim that testosterone and estrogen have absolutely zero effect on behavior impulses. If that were true, why do we have testosterone and estrogen receptors in our brains? What’s the point of doing all the logical gymnastics required to claim that there are no sexually dimorphic impulses in human males and females if one already concedes that men and women have different hormone levels, which would naturally trigger different impulses, regardless of other inbuilt sexually dimorphic traits?

What makes it even more difficult to argue that men and women are cognitively identical is the fact that mental illnesses present themselves at different rates in men and women.

We can see a person arguing that schizophrenia being twice as common in men—and depression and Alzheimer’s being twice as common in women—is somehow tied to socialization. That said, it feels almost offensive to argue that autism being diagnosed at five times the rate in men is only a product of socialization and not neurological differences in men and women given that it is recognized between 12 months of age and 18 months of age.

We acknowledge that the manner in which adults treat babies is gendered—studies have shown that baby girls are more likely to be called pretty and baby boys are more likely to hear references to their future careers—but to argue that this could lead to a fivefold increase in autism diagnoses is bananas. While one could argue that it is just that autism is merely diagnosed less frequently in girls given how differently it presents, with its actual rate of occurrence not changing between genders, the point still stands: This radical difference in presentation and recognition happens at the age of 12 to 18 months, indicating a different underlying neurology is the cause of the different presentation / diagnosis rates in girls and boys, not socialization.

If you really believe that gender differences in autism are a product of socialization, we would encourage you to run a study on the rates of autism in children raised gender neutral. If you could demonstrate that raising young boys in a gender-neutral environment dramatically diminishes presentation of some unwanted behaviors associated with more extreme cases of autism, you would be doing the world a great service.[[14]](#_ftn14)

People who claim to believe that the difference in autism presentation is due to gender socialization have not, to our knowledge, systematically tested that claim—likely because they see ideas as more of a team sport than as a tool for improving people’s lives. (We’ve actually made a note to fund a study on autism presentation in children raised gender neutral and hope to have some form of results out there by 2025; while we think the current evidence suggests the difference in autism presentation between men and women is primarily a factor of a different neurology and not socialization, if we are wrong it would be an excuse to write another book that could help a lot of people.)

A Note to Those Subject to Pseudo-Scientific Propaganda Against Sexual Dimorphism

Many individuals get exposed to skewed views of academics through pseudo-scientific articles and brief book reviews spread via social media, which can lead them to believe there is some large academic community out there that believes males and females have exactly the same behavioral impulses on aggregate. This is simply not the case. Most of the researchers and books cited by these individuals are typically making different, more nuanced arguments.

One author often cited in arguments against sexual dimorphism is Gina Rippon, who wrote “The Gendered Brain.” Rippon has been quoted as stating, “I am not a difference denier,” claiming her critics have mischaracterized her. Instead, Rippon is merely trying to argue that “biology is not destiny” and that we often overstate how much of the differences between men and women are biological: “Yes,” she writes, “there are good studies out there that show sex differences . . . but keep the context in mind” (something with which we agree). Rippon continues: “The strawman argument is that I said there were no sex differences in the brain. I didn’t say that.”

Another author often cited in this realm is Cordelia Fine, who wrote Testosterone Rex and Delusions of Gender. Fine states clearly that “testosterone affects our brain, body and behavior” and agrees that on averagemen and women have different levels of testosterone.

These authors, whose words have been twisted by extremists on both sides, often argue the following:

• That specific instances in which people assume men and women are different along gender-stereotyped lines are wrong or not backed by evidence. For example, there are not great controlled studies substantiating claims that “men take more risks” and “men are smarter,” yet these claims are both widely believed; hence, it’s worth it to attack them.
• That specific logic used in evolutionary explanations for sexually dimorphic human behavior patterns is flawed.
• That even though some behavioral impulses are, on average, stronger in men or women, it does not mean that EVERY man or woman will experience those stronger impulses.
• That environmental and social factors play a much larger role than most commonly assume.
• That as humans, we need not be slaves to our biology.

Going forward, be warned: Our theories on arousal and aversion to various sexual stimuli incorporate the potentially offensive-to-some-groups assumption that men and women have non-socialized sexual impulses that appear at different rates across genders.

Warnings aside, what if socialization actually reduces male and female cognitive differences? When looking at how individual genes are transcribed in the human brain from the prenatal period through infancy, childhood, adolescence, and adulthood, some studies found signs that that human male and female brains are most different in our prenatal states, and that they gradually converge over time, showing fewer differences with age.

One collaboration among neuroscientists at Yale, Johns Hopkins, and the National Institute of Mental Health found that the biggest female/male differences in gene transcription in the human brain, for many genes, appear during the prenatal period (for example male-female differences in IGF2 transcription are huge in the prenatal period and nonexistent among adults). Other studies show this is not limited to transcription—that a similar shift takes pace with brain structure. To explore this research in greater depth, check out: “A meta-analysis of sex differences in human brain structure” in the journal: Neuroscience & Biobehavioral Reviews.

The finding that some of the differences in male and female brains are largest before birth makes people’s insistence that socialization accounts for every single one of these differences patently comical.

Notes from the Research:

While engaging in a serious deep dive of research on sexuality, one is bound to accidentally dredge up fun studies on gender differences between males and females that don’t fit anywhere specifically. Here are some uniquely fun findings you are more than welcome to skip should you want to keep on topic:

• A study conducted by Moriah Thomason scanned the brains of 118 fetuses and found that female brains in utero produce more “long-range” networks even before birth.
• McGill University researchers found that men experience pain more acutely if they have memories of the same pain in the past, whereas women do not—or do so significantly less. This is a unique problem in its association with chronic pain conditions and was able to be alleviated through memory blockers—drugs that can separate the association of a memory and an emotion.
• A 2018 paper in Acta Psychologica found men to be more than twice as likely to cooperate in game theory games when paired with other men, versus women when paired with other women.
• Increased blood flow in the limbic areas may account for women’s vulnerability to anxiety, depression, eating disorders, and insomnia.
• Brains of females have been found to be both more active than those of males—and active in more areas. For example, the prefrontal cortex, used in higher executive functions such as focus and impulse control, is more active in women. This likely contributes to the stereotype of women having more empathy, collaboration, self-control, and intuition.
• In women, the anterior cingulate cortex and insular cortex are larger and more active during social processing. When women process sexual stimuli, the anterior cingulate cortex tends to inhibit emotion, perhaps to prevent reactions until the stimulus has been properly investigated. The insular cortex and hippocampus are both involved in the storage and retrieval of emotional memories and are both larger and more active in women than in men.
• Even some behavioral impulses that seem socialized, such as caring for dolls, may be inbred. In one tribe of chimpanzees in Western Uganda, juveniles were observed using stones like dolls. Female chimps in this tribe were seen caring for these stones three or four times more often than males, and while female chimps typically treated these stones like babies, male chimps would be much rougher with the stones, appearing to have play fights with them. No female chimp was ever observed playing with a stone “doll” after having her first baby. Perhaps females evolved a behavioral set for caring for a newborn infant and, in the absence of an infant to care for, feed this instinct through care for dolls and stuffed animals.
• On the ever-juicy and controversial subject of whether men’s preference for hotness in women (over other positive features) and women’s preference for wealth in men (over other positive features) is socialized or if there is some aspect of it being “inbred”: Alice H. Eagly and Wendy Wood created an interpretation of David Buss’s data showing that in countries with more egalitarian gender relations, the male-female differences in hotness/wealth preferences across genders were smaller, which could suggest that this difference is socialized. Nevertheless, researchers Lingshan Zhang and Benedict Jones failed to replicate the results of the previous study when re-analyzing the exact same dataset with more modern analytical techniques. Instead, work from Richard Lippa in 2010 argued that: “gender differences in personality tend to be larger in gender-egalitarian societies than in gender-inegalitarian societies, a finding that contradicts social role theory but is consistent with evolutionary, attributional, and social comparison theories. In contrast, gender differences in interests appear to be consistent across cultures and over time, a finding that suggests possible biologic influences.” It would seem, then, that the body of evidence leans toward these preferences being biological, though the jury is still mostly out. We normally don’t “show our work” when explaining nuanced points like this, but we thought we would do so in this case, both because this is a uniquely controversial subject and to give our readers a peek into how tedious the book would be if we did.

Things that Cause Arousal

If our sexual expression can be defined as follows:

What are these potential stimuli, and why are they tied to arousal? Let us explore some major categories in turn.

The systems we will be exploring in order are:

• Breeding Targets: Arousal patterns tied to systems meant to get our ancestors to have sex with things that might bear offspring (e.g., arousal from things like penises, the female form, etc.).
• Inverse Systems: Arousal patterns that arise from a neural mix-up, causing something that disgusts the majority of the population to arouse a small portion of it (e.g., arousal from things like being farted on, dead bodies, having insects poured on one’s face, etc.).
• Emotional States and Concepts / Dominance and Submission: Arousal patterns that stem from either emotional concepts (such as betrayal, transformation, being eaten, etc.) or dominance and submission pathways.
• Emotional Connections to People: While emotional connections do not cause arousal in and of themselves, they do lower the threshold for arousal (i.e., you may become more aroused by a moderately attractive person you love than a very attractive stranger).
• Trope Attraction: Arousal patterns that are enhanced through a target’s adherence to a specific trope (a nurse, a goth person, a cheerleader, etc.).
• Novelty: Arousal patterns tied to the novelty of a particular stimulus.
• Pain and Asphyxiation: Arousal patterns associated with or enhanced by pain and oxygen deprivation.
• Basic Instincts: Remnants of our pre-cognitive mating instincts running off of a “deeper” autopilot-like neurological system (dry humping, etc.) that compel mating behavior without necessarily generating a traditional feeling of arousal.
• Physical Stimuli: Arousal patterns derived from physical interaction (kissing, touching an erogenous zone, etc.).
• Conditioned Responses: Arousal patterns resulting from conditioning (arousal from shoes, doorknobs, etc.).

After exploring these systems, we will dive into a few that we originally assumed would affect arousal but—based on our data—ultimately found to have little connection to arousal patterns (like socialization and parental influence). Finally, we will do a deep dive into gender differences among these various pathways.

Breeding Targets

The first and most obvious category of stimuli that can cause arousal is tied to the systems in our brain that are meant to detect things with which we can successfully breed. This category includes visual stimulation from human body parts, smells, sexualized poses, and sexualized movements. Experiencing stimuli in this category ranges from seeing perky breasts and thinking: “Young, fertile human female: Mate!” to hearing the grunt of a large, masculine figure lifting something heavy and thinking: “Strong, genetically fit male: Mate!”

The more differentiated something is between sexes, the stronger the signal, as those things serve as better indicators of a target’s sex. This is why breasts, butts, vaginas, and the female gate (caused by the sexually dimorphic female pelvic bone) are classically the most stimulating indicators observed in a female, while firm musculature, broad shoulders, large hands, penises, and a gravelly voice (caused by a sexually dimorphic larynx) are the most stimulating indicators observed in a male. In males, attraction to feminized features can be shown to increase after an injection of testosterone, showing our response to this signal being upregulated through hormones.[[15]](#_ftn15)

While the key elements of these systems evolved to detect breeding targets, many women are aroused by stimuli that indicate a target is female and many males are aroused by stimuli that indicate a target is male even though they cannot breed with these targets.

As we mentioned before, the model placing human sexuality on a slider ranging from “totally straight” to “bi” to “totally gay”—the Kinsey scale—presents a poor schema for understanding human sexuality. Our research suggests that while attractions to male-like characteristics and female-like characteristics are sometimes bundled, in a significant chunk of the population such attractions are not associated (e.g., it is fairly common to find a penis arousing, but the naked male form and gravely voices disgusting—or to find breasts arousing, but vaginas aversive).

In one alternate (though cumbersome) model, all the breeding-partner-detecting arousal systems could be broken down into their own categories, each with their own aversion or attraction modifier, and each with their own volume. For example, one person may define their sexuality as finding penises very arousing, breasts mildly arousing, rougher male skin mildly aversive, vaginas highly aversive, and deep, gravelly voices neither arousing nor aversive.

When we first started writing The Pragmatist’s Guide to Sexuality, we were pretty sure this model could be simplified. More specifically, we thought one could probably narrow arousal patterns down to four stimuli systems suggesting something is a potential breeding partner. Anecdotally, it seemed as though systems for detecting primary sex characteristics were clustered but divorced from the systems that detect secondary sex characteristics.

• Primary Sex Characteristics = Things used to breed (penis vs. vagina)
• Secondary Sex Characteristics = Sexually dimorphic characteristics that appear at puberty (i.e., feminine facial characteristics, breasts, hip sway, a masculine voice, etc.)

Our study yielded some supporting evidence for this. It seems to be very common for an individual to find female primary sex characteristics aversive, but female secondary sex characteristics arousing (i.e., to find the feminine form arousing, but a vagina gross). Our survey shows 30% of males and 32% of females who find the female form arousing find vaginas aversive.

Our research also suggests that in the average person, the secondary-sex-characteristic-detecting system has a much higher average “volume” than the system detecting primary sex characteristics. For example, the average guy will derive more arousal from a feminine form than from a vagina. From our survey: 89% of men rate the female form at the highest level of arousal generation while only 71% rate the vagina the same way. We find it in amusingly ironic that the organs used explicitly for reproduction cause less arousal on average than secondary sex characteristics.

We developed these theories before running our survey. While there are ways we can twist our survey data to fit them, as we did above, we must be honest and admit that our data really suggests that something more complicated is going on. For example, while around 30% of the males and females we surveyed who found the feminine form arousing also found the sight of a vagina a turn off, not a single survey participant who found the male form arousing were simultaneously turned off by penises. However, 26% of men who found the sight of a penis arousing simultaneously found the sight of the male form actively aversive.

What’s more, our assumption that secondary sex characteristics are all operating on the same system may be wrong, as 15% of the women who reported to find the female form arousing in our survey also reported to see breasts as an active turn off—and yet we don’t see this happening in males. It would seem that humans may have dozens of independent arousal systems, which may or may not cluster. Weirder still, some of the arousal systems seem to cluster in only one gender (for example, in men arousal from the female form and breasts are “tied together,” but in women, it is common to receive arousal from one and not the other).

If this stuff is interesting to you, check out the supplemental chapter: “Mammary Mountain and Phallus Peak” on page 490*. It goes into great detail the specific aspects of physiology that arouse males and females and how those arousal patterns relate to each other.*

Why does all this matter? An understanding of how these male-female detection systems actually work yields a much clearer vision of a person’s real sexuality. There is a big difference between someone who has both systems turned off (and finds males and females disinteresting) and someone who has both systems in a negative state (and finds males and females icky). Given society’s current mainstream framework for understanding sexuality, we would call both of these people “asexual”[[16]](#_ftn16) despite their being just as different from each other as they are from someone who has both male and female attraction settings set to a positive state.

It is also possible for someone to receive a negative, “icky” impulse from both male and female stimuli but still receive a very strong arousal response from a separate set of cues, such as acting submissive, meaning it is entirely possible for someone to be technically “asexual,” but still have a high libido and really enjoy sexual activities tied to something like BDSM. We mention this as our data indicated that not being very turned on by naked men or women, but having a strong arousal response to certain concepts, is actually very common (oddly, this is especially true among women and men who see themselves as wealthy).

This perspective also makes it clear that the concept of being “gay” or “straight” is really more of a community identification and a description of shared experiences than it is a description of someone’s sexuality. As we mentioned earlier, “gay” is as much a description of an individual’s sexuality as “person of color” is a description of a person’s ethnicity. A woman who is not aroused by either males or females, but who is aroused by people with whom she feels emotionally close (an arousal pathway we will discuss shortly), and due to cultural circumstances only develops close emotional bonds to other women, has a totally different sexuality than a woman who has a strong sexual attraction to the female form and finds the male form repulsive—yet society would categorize both as “gay.”

Why Do Gay People Exist?

Why do gay people still exist if their sexual expression does not increase their number of offspring or the survival rate of said offspring?

One idea that has been making the rounds posits that this question is ill-conceived. Called “the gay uncle hypothesis,” this hypothesis asserts that gay individuals increase the survival rates of their relatives’ offspring, even if they have fewer descendants themselves. While there is some data to support this hypothesis, it is extremely flimsy. We personally don’t buy this hypothesis because gayness exists frequently in non-social animals—heck, it is even observed in fruit flies. A gay fruit fly is not increasing the survival rate of its brothers’ offspring.[[17]](#_ftn17)

Instead, there are a number of factors at play, all of which increase the probability of a person being gay, but none of which make it a foregone conclusion. Some of these factors are genetic; others are not. Think of it like height: Genes play some role, but so does a myriad of other factors, ranging from nutrition to in utero conditions.

Consider that every brother a man has born before him increases the odds that he will be born gay by 28% to 48%. This is an in utero effect. We know this because it still holds even when brothers are raised separately. Moreover, some studies have shown that gay men feature systematic differences in brain structure. Why does this happen? It probably has something to do with the maternal immune response to Neuroligin 4 Y-linked protein (NLGN4Y). NLGN4Y plays an important role in male brain development and mothers’ bodies get better at building antibodies that fight it with each new “infection” (pregnancy with a male offspring introduces chemicals to the female body that are identified as foreign). Eventually, this leads to later male births having statistically different neural pathways than earlier male births. This is a cool finding, as it is thoroughly backed up—there is even a study explicitly showing that mothers with gay sons have higher anti-NLGN4Y than mothers with heterosexual sons.

The fact that being gay in some males is tied to a maternal immune reaction to NLGN4Y suggests that being gay in at least this portion of gay males is not the same “kind” of neurological phenomenon as being gay in females. A mother would not produce an antibody to a female brain chemical or see it as foreign, and the stats don’t show that same correlation between same-gender siblings and female gayness. If being gay in males and females is a totally different neurological phenomenon, does it really make sense to rank them on the same Kinsey scale?

It seems likely that genes—along with other factors—play a role in gayness (genes may even play a role in the above mechanism, with some mothers having higher levels of anti-NLGN4Y). A giant study of around half a million people in the UK and the US across thirty institutions found that genetics explain about 25% of gayness.

So, if being gay is partially genetic, why did it evolve?

We are partial to the overdominance or sexual antagonism theories.

Overdominance takes place when a phenotype—the expression of a set of genes affecting an individual’s physical appearance or behavior (in this case, gayness)—exists in a population despite its contributing no benefit to fecundity (the amount of surviving offspring an individual has) because an individual who has the same code, but in a small quantity, enjoys a significant advantage.

An easy-to-understand example of this can be seen with sickle cell anemia. Sickle cell anemia sucks, and it seems weird that certain populations of humans maintain the “code” that creates it in their DNA. However, it was evolutionarily worth it to preserve this dangerous code, because those born with one iteration of it also enjoyed protection against malaria. The populations of humans who preserved this dangerous DNA did so because their ancestors lived in areas with lots of malaria and it was “genetically worth it” for them to sometimes have a child die of sickle cell anemia so long as their other children had a resistance to malaria. We are clearly oversimplifying here, but this isn’t a book on genetics; we are just trying to convey the gist of a concept.

Sexual antagonism refers to genes that lower the chance of breeding in one sex but increase it in the other. Your genes don’t magically know whether you are going to be a boy or a girl (outside those in your Y chromosome and rare genes which detect your sex before being activated), so a genetic set that increases the number of children a girl has threefold—but means a boy will have no children—will still be passed on.

The current research seems to suggest that both overdominance and sexual antagonism are at play in the expression of gayness across species.

The Fallacy of a Gay-Straight Spectrum

The gay-straight spectrum, a spectrum that presumes both males and females can be mapped on the same line based on how likely they are to be aroused by either males or females, is an artifact of a time when the concept of same-gender attraction was still a novelty and has no place in contemporary sexuality research or discussions. In addition to distorting the manner in which sexuality is investigated by forcing people into groupings incongruous with their underlying arousal patterns, the gay-straight spectrum fails to convey much about any individual’s arousal patterns beyond its demonstration that same-gender attraction exists.

The first clue indicating the spectrum does not represent real underlying patterns is that its existence implies men and women can be mapped on the same line, with a gay male being in the same spectrum “position” as a straight female. In practice, both gay and straight men tend to cluster around the extreme ends of the Kinsey scale, while women fall closer to the middle of the Kinsey scale (they are more likely to be attracted to both males and females—or at least not be actively grossed out by one gender in particular). In fact, research shows two-thirds of women show some level of arousal from pictures of both men and women. This is fairly rare in men.

Our survey showed similar results to the above-mentioned research: 83% of male respondents reported the male form to be aversive, with 59% finding it strongly aversive. Meanwhile, only 36% of our study’s female respondents reported finding the female form aversive, with only 15% finding it strongly aversive. The enormity of this disparity cannot be understated.

Were we dealing with a spectrum-based system that described male and female sexuality with equal accuracy, data taken from gay males would look similar to data taken from straight females—and yet this is not what we see in practice. Instead, the data associated with gay male sexuality presents a mirror image of data associated with straight males: Most gay men are as likely to find the female form aversive as straight men are likely to find the male form aversive. In gay females we observe a similar phenomenon, in which they mirror straight females instead of appearing in the same position on the spectrum as straight men—in other words, gay women are just as unlikely to find the male form aversive as straight females are to find the female form aversive.

Some of the research highlighting these trends has been conducted with technology like laser doppler imaging (LDI), which measures genital blood flow when individuals are presented with pornographic images. The findings can, therefore, not be written off as a product of men lying to hide middling positions on the Kinsey scale due to a higher social stigma against what is thought of in the vernacular as male bisexuality/pansexuality. We should, however, note that laser Doppler imaging systems are hardly perfect, especially when measuring arousal in females.

It is difficult to attribute these patterns to socialization, as they are observed across cultures and even within the earliest of gay communities that emerged in America, which had to overcome a huge amount of systemic oppression to exist. It’s a little crazy to argue that the socially oppressed sexuality of the early American gay community was largely a product of socialization given how much they had overcome just to come out.

If, however, one works off the assumptions of our model, this pattern makes perfect sense. There must be a stage in male brain development that determines which set of gendered stimuli is dominant, then applies a negative modifier to stimuli associated with other genders. This stage does not apparently take place during female sexual development. (We suspect this same system explains why it is common for males—but not females—to find things they are “supposed to” find gross arousing—more on this in the next chapter on page 102.)

This system must be pretty flimsy, as both men and women exist in positions all over the sexual attraction spectrum, but any theory of sexuality that cannot explain why men are either mostly straight or mostly gay across cultures—whereas women are more likely to hold positions closer to the center of the Kinsey scale—needs to be revisited.

What about the small portion of men who do rate themselves as aroused by both men and women? Actually, studies on such groups fuel our hypothesis that the spectrum-based system was misguided. For example, one study looked at the difference between men who rated themselves 5s (mostly gay) and 6s (totally gay) on a Kinsey scale. While 6s did not show any arousal when looking at gay female porn, the 5s did—BUT both 5s and 6s showed the same level of arousal when presented with male stimuli.

In other words the majority of men who are 5s on the Kinsey spectrum are no less attracted to men than men who are 6s. Instead, what differentiates these men is the presence of an entirely different, additive arousal system. The majority of males who fall in the middle of the Kinsey scale aren’t “half gay and half straight,” but could be seen as “100% gay and 100% straight.”[[18]](#_ftn18) The systems of attraction to each gender, when both active in a male, are normally not in competition with each other, but rather additive.

There are two final points we need to emphasize before we move on:

1) It is very difficult for some people to empathize with what it feels like to find one gender aversive. Specifically, people who do not experience aversion systems tied to any gender find it difficult to understand what it feels like to be grossed out by the idea of being intimate with a particular gender. If you do not experience an aversive reaction with any of your gender detection systems, try to think about a system you have that does yield an aversive reaction in you, but that others find sexually arousing.

Perhaps you find the idea of having sex with a 98-year-old aversive. That emotion you feel when you think about sex with a 98-year-old is the same emotion some people feel when they think about sleeping with someone of a specific gender. Telling someone to “just get over it” is as nuts as them telling you to get over your aversion to sleeping with a 98-year-old. Sexual aversion is an incredibly powerful emotion.

On a related note: Homophobia rates are statistically much higher in individuals with very low libidos. We suspect this is true for the same reason some pansexual[[19]](#_ftn19) people cannot understand what it is like to find one gender aversive. If you are a person who is not terribly aroused by anything, it is much harder to empathize with just how strongly others can experience sexual impulses. Given this, we imagine transphobia is likely highest not among those who are strongly attached to the sex they were assigned at birth, but those with little attachment to any gender, as they cannot empathize with what such an attachment feels like. (Our survey showed 14.5% of people fall into this category—more on this soon.)

2) Just because someone’s gender-detecting systems are not active—or just because both are turned to negative—does not mean they do not experience sexual arousal when exposed to other stimuli. We know people who would be considered completely asexual when it comes to their gender attraction systems but who become incredibly aroused by submission and humiliation. Honestly, what gender you find more stimulating is a very small part of overall human sexuality, and it is fairly ridiculous that we as a society focus so much on it.

Notes from the Research:

• Do sex hormones play a role in being queer (gay, bisexual, pansexual, etc.)?Queer women possess significantly higher levels of cortisol—a hormone regulating the response to environmental stressors—while queer men who display lower-than-average cortisol levels. One could argue this is due to living harder lives (an argument bolstered from data including black queer individuals), but queer women also boast higher testosterone and progesterone concentrations than average, whereas this difference has not been observed in men. In other words, sex hormones are probably related to the genders one finds attractive, but the power of this effect is uncertain.
• Theory: In The Pragmatist’s Guide to Relationships, we discuss how being polyamorous and sleeping with multiple partners typically increases testosterone in men, which contributes to lower body fat and more muscle. Could higher testosterone in men with several concurrent sexual partners be the source of stereotypes framing gay men as more fit/muscular than straight men, seeing as folks might be more likely to identify gay men as gay if they have several sexual partners at any given time?
• Polls show that lesbians who doubt a woman’s attraction to both women and men are generally assuming she is really just straight, whereas gay men who doubt a man’s attraction to men and women typically assume he is really just gay. It is weird that both assume that people of their same gender who are attracted to both men and women are really more attracted to men. It is also interesting that, as offensive as this stereotype is, it has an element of truth to it—for men at least (not that we don’t see this pattern in women, but the specific study we are referring to only looked at men). Around 49% of men who identify as gay identified as the variant of bisexual attracted to at least men and women before they identified as gay. This phenomenon is known as “transitional bisexuality.” When arousal patterns of this group of gay men were tested against those who identified as gay immediately, it was found they had the exact same arousal patterns as the group that had never identified as bisexual. That said, we need to be super-duper clear here that the accusation there is no such thing as a man who is attracted to both men and women has been repeatedly disproven.Some reviewers were confused as to why we made this point so forcefully: There is a common myth that, because some people attracted to both men and women are in a state of “transitional bisexuality” or engaged in “performative bisexuality” (pretending to be attracted to both men and women to secure higher quality partners of the opposite gender—e.g., a straight girl kissing another girl on the dance floor), this means that simultaneous attraction to men and women is not really a thing, which is just stupid. There are absolutely people who are attracted to both men and women.

Sexual Aversion, Looking Under the Hood

Human sexual expression is just as much a tapestry of the things that turn us off as it is a representation of things that turn us on. When exploring a specific kink or theme in erotic art, we must investigate both attractions and aversions that may have inspired it.

For example, in our survey 66% of men reported consuming erotic material focused on two women having sex and 21% of women consumed erotic material focused on two men having sex. Erotic art focused on same-gender relationships is very popular among straight communities across cultures and in a huge variety of forms, from Yaoi Dōjinshi to A/B/O, MPreg, and more vanilla “hot girl-on-girl action.” It is easy to look at the commonality of this category of erotic art and assume that we are seeing this trend because a large portion of the population finds gays to be uniquely hot or that the consumption is driven by a desire to see more people of a specific gender in erotic material (i.e., if one girl is good, then two girls is better). While this is likely the case for a portion of this population, there are other reasons a person might consume porn featuring same gender relations.

This same interest in sexually-homogenous erotic art subjects would emerge if, instead of finding gays hot, a portion of both men and women were highly turned off by seeing people of their own gender naked or in a sexual context. And wouldn’t you know it . . . that is exactly what we see. Better yet, we see this sexual expression more in men than women, and we see a stronger trend of opposite-gender-having-sex pornography consumption in men than in women. If a man finds the naked male form repulsive, he will be as disgusted by seeing a man in his porn as someone else may be by seeing a dog in theirs. If such a man wants to masturbate to two people having sex, his only option may be gay porn—well, maybe.

Futa porn (futanari), in which one of the participants has breasts and a feminine body but also a penis, presents a similar phenomenon. Remember that 26% of men who are reportedly aroused by the sight of a penis also report finding the male form actively aversive. It is likely that portion of those who consume futa porn are simply looking for porn in which they can see penis-in-vagina sex without having to see the naked male form because they find males sexually repulsive. A female mirror to futa occurs in a portion of females who consume MPreg literature, which presents a class of males capable of getting pregnant. MPreg scenarios are great for women who, while aroused by romance and impregnation, find the concept of other females in their fantasies to be aversive.

As with all sexual predilections, there is more than one underlying “sexual genotype” that can result in the same “sexual phenotype.” Two individuals may love MPreg scenarios but have a totally different underling sexuality. So just because you like gay porn because you find gay sex uniquely hot that does not preclude another person from liking it because they are repulsed by the gender not featured in it. Isolating exactly what is motivating the consumption of certain types of erotic material in varying percentages of the population is critical in getting a clear picture of human sexuality.

This is all to hammer home two often-overlooked points:

1. When trying to understand why an individual is consuming one type of erotic material over another, or why they would like to try one “kink” over another, we should focus as much on what is turning them off as what is turning them on.
2. Two individuals can have identical tastes in pornography, partners, and kinks, yet have fundamentally different sexualities motivated by different arousal patterns.

Categorization and Volume Systems

When we first started playing around with the idea that sexuality did not exist on spectrums and was instead comprised of discrete volume systems, we figured the concept was indulgently iconoclastic. Given how much sexuality affects our daily lives, we imagined society would have noticed by now if sexuality does not indeed exist on a spectrum. Thus, we were shocked by how much our survey results neatly supported the idea that sexuality is not comprised of a collection of spectrums.

You may wonder why we thought to question the orthodoxy of the spectrum arousal system even before we had our data.

Our first clue was that, even though they are common in electronics, “spectrum-based systems” are extremely unusual in nature and human psychology. While one may find a spectrum of activation of a system (e.g., a person may have a system that can be half turned on), such as the autistic spectrum or the schizophrenia spectrum, a system specifically designed to detect things along a spectrum that can then be set to any level within the spectrum upon birth is extremely weird from an evolutionary perspective, (as the gay-straight spectrum system reportedly operates).

How do these neurological systems actually work? The most common system and the type of system we think is at play in human sexuality is what we will call the “Categorization and Volume System,” which is designed to “categorize” an environmental stimulus (e.g., blue spotting patterns on an egg or something that looks like a snake) then determine an appropriate volume and impulse based on the category of stimuli (e.g., the impulse to sit on the egg or the impulse to run away). The impulse created by these systems appears at different volumes depending on what category the stimuli is placed under and the amount of the stimuli detected in the environment because they function at the same time as other systems (like the one for sitting on an egg firing at the same time as the one for running from snakes). These volumes exist as a shorthand so organisms know which impulse takes priority.

Individuals that fail to assign optimal volumes to a stimuli die at a higher frequency. For example, birds who keep sitting on their eggs despite identifying the approach of a predator may die at higher frequencies than those who abandon their nests to flee predators, thereby surviving to reproduce again. This lowers the average volume of the “eggs -> sit” system or increases the average volume of the “snake-> run” system.

Let’s consider a human example of how evolution impacts Categorization and Volume Systems. Our brains have a system that (1) categorizes a smell as the smell of a rotting corpse as opposed to a freshly killed animal and (2) drives us to get away from the meat. If this system is broken in a human, they are much more likely to see a rotting animal as a source of food, eat it, then die and fail to pass on their genes.

These systems are common because they are extremely easy to neurally program over evolutionary time. It is very common with genetic mixing for an organism to end up with more or less of a piece of “code.” If an organism is missing some of the “code” for a Categorization and Volume System, it will usually still function fine—just at a lower volume—and if the code is accidentally duplicated a number of times, it will still function fine—just at a higher volume. (This is extremely simplified—especially in the context of cognitive proclivities.)

In contrast, spectrums actually represent two systems overlaid on top of each other: One system delineating the code for the spectrum and another delineating the number that determines a person’s place on the spectrum. If a person is missing some of this code or experiences changes in some of a spectrum’s code, it often simply stops working altogether. It’s the difference between a system that operates based on piles and one that operates based on sliders. It is a lot harder to “break” a pile by mixing around the positions of its component pieces.

There is no reason a fragile slider system would evolve to manage a task as important as breeding when a volume, pile, based system is an option. To put it another way, slider-based systems require all the code for the system to “kind of” work. Slider-based systems rely on evolution only moving a person’s position on the slider and not touching the rest of the code, whereas in a volume-based system, the strength of an impulse in reaction to a certain stimulus can be increased by sloppily copying code a few times and decreased by sloppily breaking the code.

The Nature of Asexuality

We would be remiss were we to exclude asexuals—those who do not report a desire to have sex with either males or females—from our discussion of breeding target arousal. Surprisingly, it would be wrong to say that asexuals are defined by categorically not finding either males or females arousing.

At least on average, studies have shown what makes the average woman who identifies as asexual unique is not that she does not feel arousal, but rather that said arousal does not have an emotional impact on her or make her want to have sex. Asexual women, on average, generally show the same genital arousal patterns as any other female when shown pornography. What is different about female asexuals is that this arousal pattern does not generate sexual impulses. As determined by monitoring their emotional states as they watched porn, this lack of a “have sex” impulse among asexual women does not appear to stem from any fear of or discomfort with sex (or at least any more than the average woman). This implies that the majority of asexual women are not asexual out of some hatred toward or fear of sex, but rather asexual due to a general indifference toward it.[[20]](#_ftn20) (Apologies: We did not find much research on asexual men.)

If you have trouble imagining what this feels like, imagine seeing something arousing then having your genitals engorge with blood and feeling a positive sensation, but having no impulse to do anything about the situation. More of a “Hmmm, neat. Now, what was I doing again?” reaction.

The nuanced nature of asexuality in women—not necessarily being defined by a lack of arousal—is yet another reason to throw out the idea that an individual’s sexuality is largely defined by a spectrum of attraction to either males or females. If we go back to the idea of “responsive desire” versus “spontaneous desire,” the average female asexual can be thought of as someone with an extremely high “responsive desire” system if this data is correct.

Are we saying that the average asexual is still aroused by things and engages in sexual acts? Absolutely. A whopping 56% of asexuals masturbate at least monthly (contrasted with 82% of sexual people) and 60% report having sexual fantasies (contrasted with 98% of sexual people). Asexual people may merely have more expansive concepts of sexuality, seeing as 11% of asexuals with sexual fantasies had fantasies that did not include other people (contrasted with 0.5% of sexual people).

The developmental processes that make people asexual seem related to those which make people gay. Why do we say that? Asexuals are more likely to be left-handed at similar rates to both gay men and lesbians (who are also more likely to be left-handed). In addition, asexuals are more likely to be born later within a group of siblings—just like gay men. That asexuality and being gay have the same weird correlations to some seemingly unrelated factors leads us to hypothesize that the developmental pathway that leads to each state is connected in some way. This may seem obvious, but there was a possibility that asexuality could have been a totally unique phenomenon instigated by a totally unique developmental pathway.

Supernormal Stimuli, Group Sex, and Gender

There are many cases in which our gender detection systems respond to supernormal stimulation (stimulation beyond what one would receive in nature). Common examples of porn / erotic art exploiting this mental glitch can be seen with bakunyū / hyperboobs (breast inflation) and bukkake (experiencing sexual arousal when seeing someone covered in more cum than one human could produce)[[21]](#_ftn21).

Giant porn also stimulates systems to supernormal stimuli (though giant porn might also be tapping into dominance-submission attractions). We can’t help but find this kink comical in its simplicity if it turns out to act as a generic supernormal stimulus. It would mean someone’s brain is literally going: “Well if I like women, then a girl 100 times the size of a normal girl is 100 times more woman and therefore better!”

Speaking of supernormal stimuli: You might be surprised to learn that the common trope of men wanting sex with as many women as possible in a given moment is not actually accurate. One study showed only one-third of men have fantasized about a threesome. In our study, 45% of female respondents—and only 48% of male respondents—reported fantasizing about a threesome. In general, group sex is not as common as you may assume, with only 8% of straight women, 15% of straight men, 16% of non-straight women, and 25% of non-straight men reporting past group sex. Interestingly, straight women generally reported group sex experiences to be less positive than any of the other groups. Much to nobody’s surprise, women generally want threesomes to be male-male-female, whereas men want it to be female-female-male.

The Nuanced Female Detection System

The “breeding target” systems that evolved to detect females optimized for targets that were both (1) female (and therefore capable of producing offspring) and (2) young and (and therefore more likely to be fertile). This puts the feminine form in an interesting position when it comes to attracting sexual partners, as signs of female anatomical dimorphism are often at odds with signs of youth—from smaller breasts to a smaller waist-to-hip ratio. The result is an internal fight within these systems between “probably female” and “probably young.”

The arousal system used to identify optimally fertile female breeding targets ultimately creates a wide range of preferences in body types for women, some of which de-emphasize sexually dimorphic features. Collective research findings currently appear to indicate that “probably female” features are more popular among less wealthy individuals while “probably young” features are more coveted by wealthier individuals. Our survey’s data on wealthy male and female respondents who reported females arousing backs this up (we go into our stats on how wealth affects arousal in detail in the “High-Net-Worth Extravaganza” supplement chapter on page 540).

Genital Size

Though research can be mixed when the audience’s socioeconomic status is factored in, larger breasts on women generally appear to be popular. A study in France used a padded bra to test how often men would approach the same researcher with an A cup, B cup, and C cup when she was at a bar. When sporting C cup breasts, the researcher was approached by 56% of participants (versus only 26% of the time when wearing the B cup padded bra and 17% of the time when wearing the A cup bra). However, one of the “probably young” features hinted at above is that both wealthier men and women find women with smaller breasts more attractive (this has been found both in a breakdown of data from dating websites and from our own data).

Both men and women appear to appreciate larger-than-average penises, though it may be that men care more about penis size than women. One study found that while 15% of women are dissatisfied with their partner’s penis size, a whopping 45% of men are dissatisfied with their own penis size. A different study found that only 0.2% of men wish they had smaller penises, while 9% of women wish they had smaller breasts. We do a breakdown of penis size and breast size preference by ethnicity in the “Mammary Mountain and Phallus Peak” supplement chapter on page 490, which—not to toot our own horn or anything—is pretty interesting.

What’s up with Foot Kinks?

We hypothesize that a foot kink is really just a normal attraction to a sexually dimorphic part of the human body. “Foot guys” probably exist right alongside “butt guys” and “boob guys,” as all three are just different parts of the human body that are sexually dimorphic. One can even probably find a supernormal stimulus manifestation of foot kinks in the ancient Chinese tradition of foot binding (i.e., if having small feet means female, then feet the size of a plumb must be extra female). Society just happens to view people with foot kinks as odd because they are less common than arousal patterns surrounding other gendered body parts like butts or breasts.

Some researchers hypothesize that foot kinks actually represent an entirely different type of attraction caused by accidental crosstalk between parts of the brain that process foot-related and sex-related stimuli. Essentially, the part of our brain where we map the sensory stimuli that we think other people experience when touched on their feet is near the part of our brain that processes arousal. Some people think that stimulation bleeds over between physically adjacent parts of our brain in some people (we discuss crosstalk as a concept in more detail early in this book’s “Emotional States and Concepts / Dominance and Submission” subchapter on page). Suffice to say, we do not think crosstalk is the driver of foot kinks as the pattern of appearance and age of onset for foot kinks matches fixation on other sexually dimorphic body parts too closely for our pet theory to be a mere coincidence.

Some research found the level of attention to feet in a given society appears to correlate with the level of STDs in that market, with foot kinks flaring during the AIDS epidemic of the 80s, the gonorrhea epidemic of 12th century Europe, and the syphilis epidemics in 16th and 19th century Europe. That said, we think this research is bunk. While we could see that people might be pressed into finding something far away from the disease-spreading orifices and mucus membranes to sexually stimulate themselves during times of high sex-borne illness, we fail to see how humans would be able to instinctually determine the level of sex-borne illness in a population. The trigger is way too complicated to have evolved such a nuanced response . . . unless humans release some sort of pheromone when they are sick with certain types of illnesses—like some types of plants and animals do—and people’s sexuality patterns change when enough of the pheromone is in their environment. Were this the case, given the prevalence of AIDs, we wouldn’t have expected to see such a shift during the AIDs epidemic.

Inverse Systems

Onward we venture to the second major source of arousal!

In a portion of the population, some stimuli that are “supposed” to elicit an aversive reaction elicit an arousal reaction instead. It appears that a negative modifier is getting swapped with a positive during some stage of this group’s development. We call this an “inverse arousal system.”

Do you get turned on by poo, dead bodies, the idea of sex with a sibling, getting farted on, being covered in goo, sex with a geriatric patient, or being covered in insects? If so, you have an inverse arousal pathway active in your brain. All of these things are supposed to cause a strong disgust reaction, but somehow in you a “-” was switched with a “+” and something you were “supposed” to find disgusting instead turns you on.

The arousal impulse we feel when interacting with something with which we want to breed begins to develop around the age of puberty. However, some individuals report feeling strong impulses long before puberty. After puberty hits, these individuals begin to realize these feelings were sexual in nature. These prepubescent impulses tend to be associated with the two pathways: The inverse systems pathway, discussed in this chapter, and the emotions pathway, which we will discuss in the subsequent chapter. By looking at a person’s age when an arousal pattern first appears, you can tell which pathway it utilizes.

The inverse pathway is not socialized. You do not get turned on by getting covered in insects (formicophilia) because society told you were supposed to. There are three core pieces of evidence for this:

1. The types of things that activate the inverse pathway are just not the sorts of things society glorifies or sexualizes.
2. The pathway appears way too early to be influenced by socialization. Arousal impulses in this category are typically first noticed when a person is a toddler (people realize this in hindsight—obviously, people don’t understand such things to be arousing until after they go through puberty and have more points of comparison).
3. They are highly gendered in their appearance, appearing much more frequently in men. You would expect slightly more gender equity in the appearance of these arousal impulses if they were socialized or about breaking society’s rules (women get turned on by all sorts of rule-breaky things—just not these rule-breaky things).

If we don’t “learn” these arousal impulses and if they do not boost our odds of reproducing, where on earth do they come from?

Evolution is a cheap programmer when it comes to behavior. Evolutionary forces often hijack or piggyback on systems that were originally evolved in reaction to some other evolutionary pressure. Unfortunately for us humans, it looks like our sexuality is affected by evolutionary frugality and the same neural pathway fires when we experience aversion in sexual and non-sexual contexts. This results in our experiencing the same “ick” reaction when imagining an encounter with centenarians having sex that we feel when we fall face first into a pile of dog poop.

While we covered this a bit already, it is worth going over again: The aversion system in humans is literally the exact same system as the arousal system. It just uses a negative modifier.

Think about it, you walk into a room and see a rotting corpse. How does your body instinctively respond?

• You look away
• Your pupils contract
• You either hold your breath or hold your nose
• You try to get out of the room as soon as possible
• You have a strong impulse to not interact with the thing

Now suppose you see a hot person when you walk in a room. This time:

• You look at them as much as social conventions allow
• Your pupils dilate
• You might inhale deeply
• You look for excuses to stay around
• You have an impulse to interact with them

These two systems aren’t just eerily similar; they are the same system. The fact that this aversion pathway sometimes breaks in a way that causes strong arousal is proof of that in our minds. There is no other good explanation for why inverse arousal pathways appear before puberty, are heavily gendered, or really exist at all—but more on those three points ahead.

It makes a lot of sense that these two systems would be operating off the same code. Of all the categorization and volume systems animals have, the two (not tied to eating) that would have evolved earliest are:

1. The one that tells an animal to mate with something, and
2. The one that tells an animal that if it stays in an area with something, it may become ill.

The brains in which these systems evolved to work would have been simple in the extreme. If evolution could have found a way to program these systems with the same “code,” it would have. In the same way the original Mario games used the same image file for both bushes and clouds to save space because old cartridges had so little memory, when our brains operated in simple worm-like creatures, evolution decided to use the same system for arousal and aversion.

Sometimes part of the “code” that is supposed to find something aversive gets switched with the impulse to find it sexually attractive. Essentially, a (-) gets swapped with a (+) in a small portion of the population. This explains why people who have impulses tied to these things report feeling them before puberty. Systems like the one that keeps you from playing with fecal matter or rotting corpses are meant to be in an “ON” state from birth and not switch into an “ON” state at puberty, as those things are always a threat.

Note from the Research:

• An attraction to dead bodies motivates only 15% of necrophilia cases.

Inverse pathways leading to arousal are less common in women. We think this gives us a hint as to the source of this switch. Men tend to cluster along the far ends of gay-straight spectrum scales, whereas women do not (a gay man is more likely to be grossed out by the idea of sleeping with a woman than a gay woman is a man, plus a straight man is more likely to be grossed out by the idea of sleeping with a man than a straight woman is a woman). In men, there is some sort of neurological system designed to “flip” +s to -s that is not commonly present in women. We suspect this sign-flipping mechanism sometimes flips random +s and -s in roughly 15% of the male population and 5% of the female population, causing these individuals to become aroused by one or two random things that evolved to gross them out at a volume equal to what was supposed to have been output in disgust (this same switch also has the potential to cause someone to become disgusted by something that is “supposed” to arouse them).

Why would there have been stronger pressure on men to develop this system? Consider that if a man is sleeping with ten random people he finds attractive every couple of months, the fact that three of them just happen to be men is going to affect the number of children he has far more than a woman sleeping with ten random people every couple months, three of which just happen to be women. It appears that men addressed this greater potential for loss by developing some system that recognizes their gender of primary attraction, then flips the switches associated with the other gender to negatives early in childhood. The system, however, can be a bit faulty: Sometimes it flips the wrong switches and whatever process developmentally flips arousal to aversion is identical to the process for flipping aversion to arousal.

In short, many things you find gross at an instinctual level—usually from childhood—will turn on a small portion of the population; however, this is not true for other emotional states. For example, just because you have an instinctual fear of something does not mean a portion of the population finds that thing hot. While there are not large populations that get turned on by things like fire or heights, there are large populations that feel turned on by things like having insects poured on their face, being farted on, or being covered in slime.

Zoophiles

One kink group that may be tied to inverse systems (due to its overrepresentation in males and early age of onset) is zoophilia/bestiality. Both of these communities are aroused by the idea of sex with animals and both are surprisingly common. Kinsey’s study back in 1948 found 8% of men and 3% of women had had sex with an animal, but with time these numbers have dropped, with more recent studies showing them at around 5% and 2% respectively (likely a product of lower access to animals in a more urban society). These numbers are fascinating when contrasted with our survey results, which suggested that only 6% of males and 2% of females are aroused by the idea of sex with an animal.

If the data is accurate, this indicates around 87% of people who are aroused by the idea of sex with an animal have tried it. This suggests the impulse must be incredibly strong in the portion of the population that experiences it, lending support to our theory that volume modifiers are developmentally separated from the +/- signs. The volume of the disgust generated by the idea of having sex with an animal is super high in the average person, so the arousal generated by the idea would be equally high to someone turned on by it—high enough to override the moral aversion in almost every individual who experiences this arousal pattern.

As is the case with many kinks, zoophilia and bestiality seem to be combining a few pathways. Interviews with zoophiles often cite an attraction to animal genitalia due to their novelty (specifically, in one survey, they said this attraction stemmed from the genitals being smellier, wetter, and harrier). Individuals aroused by this aspect of zoophilia and bestiality are likely being turned on by an inverse pathway that would normally create an aversion impulse at the thought of sex with something that was smellier, wetter, harrier, and well . . . not human. However, not all zoophiles are experiencing the same pathway tweaks; some are likely exercising a sub-dom arousal pathway and others still seem aroused by the idea of sex without fear of judgment.

Notes from the Research:

• Most zoophiles are specifically aroused by the idea of sex with dogs or horses. We suspect this may just be due to the high availability of dogs and large genitals of horses combined with their moderate availability.
• One study on the subject found the average zoophile has sex with an animal two or three times a week.
• 72% of zoophiles responding to one study reported to not see anything wrong with what they were doing and 80% claimed that they believed the animals had offered them consent. As much as we have an impulse to condemn such acts as inconceivably reprehensible and remind our readers that animals cannot give consent, we would be hypocrites to do so as people who love to eat veal, enjoy a fresh glass of factory-farmed milk, and delight in playing with adorable dog breeds whose unique features are the product of forced sex between dogs. It is critical that we not shield ourselves from condemnation just because the way we lead animals to be tortured and forced to have sex is socially condoned. (But seriously, animals cannot consent.)

While we are on the topic, we would be remiss to not mention a bizarre website that used to exist in the early 2000s, which featured an excruciatingly detailed guide for having sex with dolphins. It went through everything from where to buy a house and how to get to a location where dolphins congregate to how to sexually engage them. What makes it crazier is that dolphins have a prehensile penis (i.e., their penises are like an elephant’s trunk), which could easily kill a person should they fail to execute every aspect of the courtship perfectly. The thought of a person who bought a house near a specific cove just so they could try to have sex with dolphins presents a splendid summation of just how far people will go to satisfy atypical sexual impulses that are very likely to get them killed. Humans are utterly bizarre.

Emotional States & Concepts / Dominance & Submission

Now to the arousal pathway we personally find most interesting: The pathway tied to emotional states and concepts—dominance and submission among them.

Emotional states and concepts can yield sexual arousal, but unlike the previous pathways we have discussed, emotional states and concepts can begin to cause arousal at any point in a person’s life, sometimes appearing before adolescence and other times appearing in adulthood. (As a refresher: Breeding target pathways almost always appear around puberty and inverse pathways almost always appear very early in life.)

The concepts and emotional states that ultimately trigger arousal appear to only be those which are most deeply programmed into us—those which would have been extremely relevant to humans in our early most stages of social evolution, when humans were tribal animals. Specifically, the emotional states most likely to be looped in with sexual arousal are associated with concepts such as: Submission, domination, anticipation, usefulness, betrayal, trust violation, the ability to impose an emotional state on another, rape, worthlessness, helplessness, being hunted/hunting, humiliation, feeding another, freedom/slavery/servitude, impregnation, surrender, dependency, being depended upon, gift exchange, subjugation, killing, being consumed, and predator-prey relationships.

In contrast, evolutionarily recent emotions and concepts, such as schadenfreude, war, driving, or the feeling you get from reading a good book, are rarely seen to be associated with sexual arousal. Something about these very early concepts and emotions, which played such an important role in our survival as a social species, got tied to arousal states in a portion of the human population.

The current go-to theory on this is that neural crosstalk plays a significant role in the connection between emotions, concepts, and arousal. Have you ever had the audio cord that connected to a speaker system get too close to a power cord, leaving you annoyed by the random noises that resulted? Essentially, this hypothesis claims something similar is happening when a person gets aroused by this category of stimuli.

The part of our brain that creates arousal impulses is nested between parts for social processing and the part of our brain for processing stimuli related to feet (this is unusually large in our brains, presumably because it was important back when our feet were used to grab branches). Many theorize that in a portion of the population, there is crosstalk between these older social parts of our brain and parts associated with sexual arousal. Essentially, a bunch of neural activity in one area could cause neural activation in adjacent areas or lower the threshold for activation in those areas.

We suspect that brain overlap theory is partially correct—or at least that it explains a small portion of cases in which a social concept arouses an individual. We do not, however, believe that brain overlap is the primary driver of conceptual arousal. If it were, we would expect a more even distribution of emotional concepts that arouse people, and this is not what we see in practice. Instead, emotional states that can be framed in the context of dominance and submission are far more likely to be tied to arousal pathways. Even more damning to this theory is the gendered nature of these pathways—something that is unexplainable by crosstalk alone as these parts of the brain are in the same locations and are roughly the same size in both males and females.

The role of dominance and submission in human sexuality cannot be overstated. Our survey suggests that the majority(over 50%) of humans are very aroused by either acting out or witnessing dominance or submission. But it gets crazier than that: While 45% of women taking our survey said they found the naked male form to be very arousing and 48% said they found the sight of a penis to very arousing, a heftier 53% said they found their partner acting dominant in a sexual context to be very arousing. Dominance is literally more likely to be very arousing to the average female than naked men or penises. To say: “Dominance and submission are tied to human arousal patterns” is more of an understatement than saying: “Penises are tied to human arousal patterns.”

We have a delectable theory about what is going on here: If you look at all the emotional states that frequently get tied to arousal pathways, the vast majority of them seem to be proxies for behaviors that would have been associated with our pre-human ancestors’ and early humans’ dominance and submission displays. For example, things like humiliation, being taken advantage of, chains, being used, being useful, being constrained, a lack of freedom, being prey, and a lack of free will may all have been concepts and emotions important in early human submission displays.

We posit that most of the time when a human is turned on by a strange emotional concept—being bound for instance—their brain is just using that concept as a proxy for a pre-human submission display and lighting up the neural pathways associated with it, creating a situation in which it looks like a large number of random emotional states are turning humans on, when in reality they all boil down to just a fuzzy outline of dominance and submission. Heck, speaking of binding as a submission display, there were similar ritualized submission displays in the early middle ages, in which a vassal would present their hands clasped in front of their lord and allow the lord to hold their clasped hands in a way that rendered them unable to unclasp them (this submission display to one’s lord is where the symbolism of the Christian kneeling and hands together during prayer ritual comes from). We suspect the concept of binding and defenselessness have played important roles in human submission displays well into pre-history. Should all this be the case, why on earth have our brains been hardwired to bind (hehe) our recognition of dominance and submission displays to our sexual arousal systems?!?

Dominance and submission displays are near universal in social animals. Sociality doesn’t really work in intelligent species when a tribe doesn’t know which members’ preferences take precedence or if they have to fight every time there is a difference of opinion. When our ancestors first evolved sociality, the brain had to find a way to motivate these social-order-facilitating dominance and submission displays. It is not crazy to think the brain used arousal to motivate these displays instead of a more generic reward pathway, given how close the part of our brain that judges our position in a social hierarchy is to our arousal centers. Further, if we assume that evolution was using arousal to reward dominance and submission displays, we doubt it had enough evolutionary time or incentive to quarantine this connection to only dominance and submission instead of associated concepts like predator-prey relationships, humiliation, and bondage. This would explain why there is such a range of dominance or submission associated concepts that arouse people.

There was likely another reason why evolution “chose” the arousal pathway to motivate dominance displays instead of a “more appropriate” reward pathway. When our pre-social ancestors were first evolving submission displays and needed a system to motivate complex behavioral displays, they likely already had one: The system used for mating displays (think of a bird dancing about and chirping in order to show another bird how great his genes are). Given its proximity to the act of sex, it makes sense that the mating display system would be using arousal pathways to motivate it and encourage action when it was detected in others.

It would have been much “cheaper” to just make some tweaks in the mating display system instead of building a whole new system from scratch—and since evolution is a cheap programmer, it would be odd for evolution to not borrow pieces of the existing mating display system to build the dominance display system. We are therefore willing to bet this cheap programming, as it were, explains why the majority of humans experience arousal when performing or witnessing dominance and submission displays.

A similar pattern can be observed in all sorts of social mammals: The same behavior used to show one is ready for sex is also used as a submission display. In most of these species, the way a female signals she is ready to be mated with involves a set of displays very similar to the ones that show submission to a more dominant tribe member. Heck, among many animals, all the nuance is taken out of it, and one individual, male or female, will simply mount another to show it is dominant while another—male or female—will prepare themselves to be mounted to show they are submissive.

Some species are strictly matriarchal, such as the spotted Hyena. Instead of adopting a behavior that mocks a female being ready to be engaged in sex as a submission display, such species mock a male being ready for sex as a submission display—with an aroused penis being a sign of submission in spotted hyenas in both males and females (females of this species have something called a pseudo-penis, hence this being possible). Long story short: The connection between dominance and submission and arousal is not a “human thing;” it is a “most social mammals” thing.

People often think of dominance and mating displays as sets of actions and not concepts; however, many animals’ mating displays are inherently conceptual. Think of the bird that brings a “gift” to a potential mate to show how good it is at procuring things. This is a conceptual display in the sense that the female must judge the quality of the gift. If a mating display system were to be hijacked to create human dominance and submission displays, those displays could easily be conceptual. Behaviors such as bowing, turning our heads to the side to expose our necks, and clasping our hands together are pretty clear instinctual actions showing submission in humans (likely to make ourselves look smaller or expose vulnerable regions of our bodies), but there are also concepts that can signal dominance or submission such as humiliation, bondage, control, chains, and slavery.

To see why concepts like dominance and submission that seem silly in modern human culture were so critical to our early ancestors, take a step back from what dominance and submission mean in the context of BDSM and our current culture and consider what dominance and submission meant to our ancestors.

For the sake of argument, let’s use chimpanzees as a proxy for our early social ancestors. Almost no cognitive ability affects a chimpanzee’s survival more than its ability to understand its position within a tribe’s social hierarchy and signal that it understands its position to other members of its group. A chimp who cannot understand when another chimp is above it in the dominance hierarchy and signal that it understands its lower social rank through a submission display has almost zero chance of surviving. It is not an exaggeration to say that a chimp who does not know how to find its own food has higher odds of survival than a chimp that fails to understand its position within his or her tribe’s social hierarchy.

To create dominance hierarchies, chimps must have a repertoire of dominance displays and submission displays deeply ingrained in their behavioral sets. When you see BDSM in this context, it becomes quite comical: A ridiculous Kabuki theater for acting out early hominid dominance and submission displays that in turn piggyback off of the “code” used to motivate pre-human mating displays, all to masturbate a very specific neurological pathway.

Similar to attraction to either males or females, arousal/aversion from dominance and submission does not work on a spectrum, functioning instead as two independent systems. Just as a person can receive emotional rewards from the systems for detecting men and the systems for detecting women, a person can also be turned on by performing/watching both dominance displays and submission displays. The same way a person can be turned off by men and women, a person can be turned off by both dominance and submission displays.

Much to our fascination, it seems to be possible for a person to be turned on only through one specific subcategory of dominance or submission. For example, someone may only get turned on by the feeling of being constrained or humiliated—and no other aspect of the submission pathway. We are unsure why this happens, though our survey shows such narrow and specific tastes are rare. In our survey, most people who are reportedly turned on by one subcategory of submissive behavior also reported being turned on by submission in general (the same goes for dominance related behavior).

Notes from the Research:

• Female submissives (at least on the BDSM front) have lower empathy than average females.
• While BDSM is often conflated with abuse, surveys indicate that 70.8% of women participating in BDSM report that BDSM reduces psychological stress “always” or “almost always.”

Being Bound

Arousal from being tied up or immobilized is strikingly common (45%f and 23%m). It is easy to assume that the impulse driving this behavior comes from being bound serving as a submission display—and sure we can see a rope bunny who gets aroused by being tied with rope maybe deriving arousal from a submission pathway, but not every outlet for this kink looks like a clean-cut proxy for submission.

Consider latex vacuum beds in which all the air is sucked from a vacuum bag, completely and tightly immobilizing a person. This is well-known in BDSM circles, is seen as an extension of the latex and PVC rubber kink, and (contrary to popular opinion) did not arise in Japan, but likely emerged in Western Europe instead. Given how clinical and separated from potentially historic interaction patterns vacuum beds are, they do not seem like anything proximate to a classic submission display.

So, what do we think might be going on here? We think that a portion of “kinks” around being bound or otherwise immobilized are not actually kinks at all, in that they are not motivated by an arousal impulse. Instead, we posit certain interests are widely believed to be driven by an arousal impulse, not because they are motivated by an arousal system, but because the types of places that accommodate them (such as BDSM dungeons) typically focus on arousal pathways.

What if positive emotions from being bound represent a misidentified impulse? What if the positive emotional feedback actually felt by individuals indulging in these kinks is a swaddling impulse that doesn’t turn off fully in a portion of the population? For those who have never cared for a baby: Human infants take immense comfort in being snugly swaddled. It would almost be weird if there was no portion of the population that didn’t have this impulse “shut off,” especially when you consider there would not be a strong evolutionary pressure to ensure we only feel the swaddling impulse in infancy.

That we can’t look around and identify the portion of adults whose swaddling impulse never turned off suggests they are being obscured by some other group or behavior. We suspect that these people make up portions of the populations involved with what is traditionally thought of as bondage, recreational use of weighted blankets, and obsessively tight tucking in of sheets.

This is one of those things to always be careful about when trying to parse out drivers behind a human behavior pattern. When you are looking at behavior from the perspective of arousal impulses, it is easy to forget that not every weird mental pathway must be driven by an arousal system, there are plenty of good feelings that don’t come from arousal systems and not everyone compelled to a non-socialized behavior pattern are doing it because of an arousal system.

Dominance in Self vs. Others

One interesting thing we decided to test for in our study was whether there was perfect overlap between people who feel aroused by seeing their partner acting dominant in a sexual context and acting submissive themselves in a sexual context. There was not.

It is actually quite common for a person to not be aroused by acting submissive themselves in a sexual context and yet to find it very arousing to see their partner acting dominant. The inverse is also true.

We find it a little odd that the systems shook out this way, but being aware of the dynamic is useful when mapping a person’s sexuality.

The Non-Sexual World of BDSM

When some small sliver of a subgroup toys with sexual arousal, our society tends to perceive the entire community as primarily focused on sex. This tendency can obscure totally-non-sexual factors that draw many (if not most) members to these groups.

Given the theming of this chapter, let’s consider the BDSM community as an example. Many BDSM community members are attracted to the subculture by totally non-sexual interests. For example, BDSM scenes can induce something called “subspace” in the submissive individual (this comes in a number of variations, including petspace, ponyspace, and littlespace). Subspace is a trance-like state that combines a constricted perception of reality with a sense of euphoria capable of transforming the perception of other stimuli (i.e. pain might be perceived as pleasure). Depending on the individual, this experience can be completely non-sexual and yet it presents a huge appeal of BDSM to a significant number of participants in its adjacent communities.

Don’t misunderstand us—even subspace is not the major non-sexual draw for the majority of BDSM practitioners. There is a broad diversity of motivating factors drawing people to BDSM, ranging from a sense of community to the opportunity to master new skills and the manner in which BDSM roleplay allows people to assume new roles that extricate them from the doldrums of daily life.

Very, very, very few communities of any type are predominantly focused on sex or sexuality—this is probably why whenever any community is sex-adjacent in any way, outsiders assume it is all about sex. We see this phenomenon affecting communities as diverse as diverse as the poly, leather, pony play, Second Life, and furry communities. Consider how, as kids, when we first hear about dating and marriage, we think it’s all about kissing and sex, but as adults we come to see those things as making up less than 1% of the holistic dating/marriage experience and representing very little of dating/marriage’s appeal.

One Way We Could Be Wrong

Our data suggest that 80% of women who tend toward the center of the gay-straight spectrum are aroused by submission, contrasted with only 62% of straight women. Recall how women in general in our data reported being more aroused by submission than the naked male form or penises. What if this explains why women are more likely to fall in the center of a gay-straight spectrum than men?

What if all our theorizing about an inverse system is just coincidence, and what is really going on is that women predominantly have a dominance-oriented sexuality? Could it be that the mostly-male lens through which sexuality has historically been investigated has led researchers to incorrectly assume that if males have a “naked-female-focused” sexuality, women must in turn have a “naked-male-focused sexuality?”

More females than males may appear to fall around the center of the gay-straight spectrum because more women’s dominance-detecting systems eclipse those meant to detect gender (meaning these women are not necessarily pansexual, but rather more attracted to dominance or submission than any particular gender). In this case, while many women placing around the center of the gay-straight spectrum in surveys would indeed be “bi” in the classical sense of being actively aroused by at least men and women,[[22]](#_ftn22) others would merely be women whose gender detection systems pale in comparison to their dominance-detection systems. Even if members of this second group were not aroused by anything tied to females, the relative volume of their female-detecting systems when contrasted with their dominance-detecting systems might be so weak that they would glean more arousal from a very dominant female than they would from most men.

We still don’t like this theory as much as the larger framework we present, but it may represent another way of looking at the larger truth.

Note from the Research:

• Can an emotion like fear increase our attraction to someone? A famous study conducted in the 1970s that reported to show that men who interacted with women in a dangerous situation felt a stronger bond with them than those who did not. Specifically, researchers had a girl interview men on a fear-inducing suspension bridge and on a normal bridge and recorded whether these men reached back out to the girl more often when the interview happened on the fear-inducing bridge.

This study has since been picked up by pop culture both due to its clever design and the fact that it yields a surprising result while simultaneously validating a hunch people kind of believe is true (these are the sorts of studies that spread the most, like that garbage study about babies and classical music). We would not take this study’s findings as strong evidence of its claims. Obviously, people who interviewed someone in a unique and interesting environment and thus have an “excuse” for outreach are going to follow up with someone more than those who didn’t.

We mention this study to highlight the relative absence of strong evidence that emotional pathways outside of disgust, love, and dominance/submission proxies have ties to arousal.

Transformation

BDSM, bondage, slavery, and humiliation are clearly tied to the dominance/submission pathway of arousal, but what about some of the less obvious kinks related to this arousal pathway? Transformation presents one interesting example.

The key to unlocking the mystery of what causes people to be aroused by the idea of transformation involves exploring the gender breakdown of transformation arousal (f16% m5%) and the variable age of onset. With this information, we can confidently say that transformation scenarios activate the human submission pathway.

As with most kinks that lean female, most transformation “porn” manifests in the form of narrative fanfictions and romance novels—typically, werewolf and vampire stories. The narrative structures of fanfiction and romance novels allow us to focus on the emotions experienced by characters during transformation fantasies, which in turn enables us to pinpoint what specifically triggers arousal. Arousal triggering emotions in transformation-focused romance novels and fanfictions typically fall into one of two categories: Either the transformation purifies the individual, making them somehow “cleaner” and more perfect, or the transformation revolves around pain, a lack of control, dehumanization, and/or surrender of control to another individual, who assumes a dominant role over the individual being transformed (Think: Sexy male vampire transforming a woman into a glittering vampire or a woman, recently attacked by a bloodthirsty werewolf, having her bones painfully crack and reshape as she becomes a beastly werewolf and loses control of her actions).

One interesting exception can be observed with superhero and magic anime girl transformations, which involve empowerment of the individual being transformed. While such transformations are often sexualized, they do not inspire the same amount of porn or erotic fiction as, say, werewolf, vampire, and animal transformations. This suggests that superhero / magical anime girl types of transformation are not effective at activating a transformation kink. This is neat because less sexualization of empowerment-based transformation makes sense if the above framework is correct—that transformation is a proxy for submission.

The counterpoint to the above argument is that transformation is actually overrepresented in females because it has something to do with pregnancy. Women have a portion of their life cycles in which their body rapidly and dramatically transforms, whereas males do not. We do not buy this theory but wanted to point it out as another option.

Signs That our Framework May Be Wrong

Some emotional state associated kinks do not seem to reinforce our framework. We are never ones to hide evidence that we may be wrong, so let’s take a quick look at four of these: Poppers, looners (those who engage in balloon play), voyeurs, and those aroused by sex in public spaces.

Poppers deviate from our model that implies all emotional turn ons are proxies to the dominance-submission pathway. While popping could be seen as engaging dominance-submission pathways (in that somewhat-unpredictable inanimate objects over which people do not have total control can be seen as being the dominant figures in a scenario), we hesitate to say this connection is definitive. Kinks of this sort may genuinely exemplify a case of crosstalk: If you tickle the part of the brain associated with anticipation—or non-sexual stimulation from certain emotional states like anticipation/release—enough, for whatever reason, it may directly affect the arousal system in a portion of the population through a potentially-unique pathway. Alternately, these kinks may involve a source of non-sexual stimulation being mislabeled (we suspect this happens frequently, with unusual sources of positive stimulation getting looped in to “sexuality” even when they are not activating arousal systems because they often take place within sexual contexts—for a more generic, if imperfect, example of this, think of a massage).

Looners gain arousal from sexual scenes involving balloons. From what we have learned from community members, interest in balloons arises before puberty, indicating it is either an inverse pathway (which we doubt) or an emotional state pathway. The problem is we can’t pinpoint exactly what emotional state balloons might be tied to. One community member we interviewed said they contextualized it as part of the BDSM community and to them it was an extension of submission or a tool for use in eliciting submission pathways. If this particular looner is right, it would be in line with our theory that all emotional state pathways are really just proxies for dominance and submission.[[23]](#_ftn23)

Voyeurs and those aroused by public sex may seem to be related on a superficial level but run off totally different arousal systems. Voyeurism is likely just a “breeding target” pathway functioning normally. The abnormal aspect of it lies in the lack of aversion the average person evolved to feel when they see the target of their sexual interest with another person. That said, many who practice voyeurism say the aspect of “betraying/violating” their target through watching is an important aspect of the arousal pathway, which would indicate a purer emotional pathway. While this might be a proxy for dominance, we doubt it.

Public sex seems to be motivated largely by the fear or heightened emotional state created by the risk of being caught. We suspect this is also a genuine case of crosstalk (we didn’t collect the data necessary to see if there is an overlap in these kinks, but if our crosstalk theory is correct, there would be).

Notes from the Research:

• One survey found that 66% of male and 57% of female participants had fantasized about the thought of public sex. Two predominant emotions appear to be at play here: “putting on a show” and “anticipation from fear of being caught.”
• Studies indicate that roughly two-thirds of men and one-third of women report having fantasized about voyeurism. Our survey showed 23% of females and 35% of males consume erotic material related to voyeurism. Personal accounts from voyeurs suggest they derive pleasure from the emotional states of their targets, specifically their targets’ suspicions of being watched or the concept of “betrayal” associated with their actions towards their targets.

Emotional Connections to People

Some people—heck, most people—feel a sexual impulse when exposed to stimuli they associate with a person to whom they are emotionally connected, or at least experience a lowering of the threshold required to feel a sexual impulse created by other pathways. Some people—demisexuals—only experience sexual stimulation in concert with strong emotional connections. This arousal pathway kicks in during puberty. (Note: The Westermarck Effect is why you don’t end up attracted to family members even though you have a strong emotional connection to them; we discuss the Westermarck Effect in detail later in this chapter).

It is easy to understand why humans evolved to experience greater sexual arousal from those to whom they have an emotional connection. This development facilitates pair bonding, increasing the odds that people will care for any offspring they have together. Amusingly, our brains are not designed to separate an emotional connection with a real person from an emotional connection with a fictional person, so almost any popular show, book, or movie will end up with an immense amount of porn dedicated to it.

The fact that fictional characters activate this pathway gets interesting when people form attractions to characters that you really would not expect to see sexualized. Consider the porn generated by the large adult fan bases surrounding children’s shows, such as “My Little Pony” and “Transformers.” Alternatively, consider the “fake” porn created of people with a public profile (and not just actors). Even Sarah Palin has had her share of erotic material created about her.

Despite stereotypes to the contrary, enjoyment of erotic material related to known characters is not the exclusive purview of “weird male loaners.” A robust 8% of females and 9% of males in our survey reported consuming erotic material depicting pop culture figures targeted at children, while 11% of females and 16% of males reported consuming erotic material focused on pop culture figures targeted at adults. This gender parity should not be surprising, as preferentially wanting to mate with individuals to whom someone has an emotional connection is evolutionarily beneficial to both males and females. This gender parity is only surprising because society has created a default assumption that all sexually deviant activities skew male.

Fan bases have been sexualizing cherished characters since at least the 1920s, which saw the emergence of little porn books called Tijuana Bibles (also known as eight-pagers, Tillie-and-Mac books, or jo-jo books). These publications were typically purchased under the counter from bars, bowling alleys, garages, barbershops, and second-hand bookstores. Tijuana Bibles featured popular characters of the time, such as Popeye, Blondie, Dick Tracy, and Little Orphan Annie in sexualized contexts. We would bet that this behavior goes back much further. It is possible, for example, that sexualized political cartoons alleging that Marie Antoinette had lesbian relations with the duchess of Pequigny were more driven by this sexual drive than any political gripes, and that as long as humans have been forming emotional attachments to fictional characters, they have been finding ways to create stories that sexualize them.

Emotional connections might also stand at the root of the aversion impulse most people feel when someone with whom they feel emotionally close engages sexually with another person. In other words, if you have an emotional connection to a person or a fictional character, you will likely find the idea of them having sex with someone else gross and be similarly repulsed by the idea of someone else masturbating to them. In a small portion of the population, this aversion reaction is flipped (as happens with any attraction or aversion impulse per our theory).

An inversion of the disgust most people feel when they see someone to whom they are emotionally connected engage sexually with another person likely explains the drive behind a portion of the hotwife/cuckold community. We would argue the drive to see someone with whom you share a strong emotional connection have sex with someone else is not primarily driven by a desire to be humiliated as is often assumed by outsiders (though humiliation certainly does play an important role for a portion of the community). If “hotwifing” is indeed driven by an inverse pathway, this would also explain why the behavior is so overrepresented in men (f11% m17%), as inverse pathways do not occur as frequently in women, (conversely, if it was over represented in females, we could assume it was motivated by the dom/sub pathway, which is seen more in women).

Contrary to what pop culture would have you believe, the tendency to perceive individuals to whom you have an emotional attachment as more attractive is incredibly strong—even among long-term romantic partners. About 90% of people have sexual fantasies about their current romantic partner, and two-thirds have these fantasies frequently, whereas only about 10% of people frequently fantasize about Hollywood celebrities, porn stars, politicians, or other famous people. Interestingly, while fantasizing about your partner is shown to increase the quality of your sex life with them, research has also shown fantasizing about other people is not linked to a decline in a couple’s sex life (though after a breakup, people will often look for “evidence” like this that the breakup was inevitable).

This category of arousal is one into which label-happy individuals have really sunk their teeth. The most common label related to this connection between increased arousal and emotional connection is “demisexual” to denote an individual who has emotional connection as their primary arousal pathway. People with a sign flip, who receive aversion from this pathway (e.g., they find the thought of sex with people to whom they have a strong emotional attachment aversive) are called “akoisexuals” or “lithsexuals.” “Lithromantic” is a term for individuals who primarily derive arousal from this pathway but have aversive reactions through enough of their other pathways that they prefer to fantasize about relationships over actually being in them.

Rather than assign a litany of labels to different types of sexuality, we prefer to clearly describe sexuality by stimuli, reaction, and volume. We see ultra-specific labels, such as “lithromantic” as inefficient because no one has time to remember them all. A word to which only you know the definition isn’t useful at transferring information to another person, which is, well . . . the purpose of language. (Not that we think people should abandon words describing specific sexualities: These ultra-specific terms can help people feel more comfortable with their sexualities and provide a sense of belonging. However, when it is presumed that sexuality is primarily described through specialized terms, they run an equal risk of causing someone to feel forced into a sexuality only adjacent to their own—or isolated, should an adequate term for their particular sexuality not exist.)

Sex Without Emotional Attachment

Individuals with an inverse pathway in relation to emotional attachment get turned on when they see others hooking up with people to whom they are emotionally attached (in the form of cuckolding). We also see something of an opposite phenomenon in which people feel rather turned off by the idea of sexual intimacy with someone to whom they feel emotionally connected (this is what the term akoisexual is meant to describe). Just as a small portion of the population will find typically aversive things to be arousing due to a sign flip, an equal portion will find something normally arousing to be aversive, which is the dynamic at play when people feel grossed out by sex with those they love.

Such people often fantasize about sex without an emotional attachment. This is pointed to as one of the major drives behind bestiality by zoophiles (in studies exploring what drives people to want to have sex with animals). This desire for sex without emotional attachment may have added some fuel to the broader “sex robot” trend, with one (admittedly non-peer-reviewed) study showing 11% of females, 17% of males, and 23% of non-binary individuals reporting having fantasized about it (7% of women and 8% of men responding to our survey reported consuming erotic works involving sex with an android). Still, 70% of people rarely or never fantasize about emotionless sex, meaning that wanting an emotional connection to a partner is the norm.

Laughter & Attraction

Much to our surprise, we could not find any study that showed laughter directly leading to arousal in and of itself—outside of neurodivergent case studies. That said, laughter does seem to promote emotional closeness in a large portion of the population, which in turn makes arousal more likely to form. Studies have shown that the more times a guy can get a girl to laugh, the more likely the girl will be to want to date him (though even a stronger metric on this front is the number of times both partners laugh at the same time during their first encounter).

Why do people bond more quickly with those who are funny? Surprise: It’s not that being able to make someone laugh should be seen as a proxy for intelligence. In fact, University of Kansas researcher Jeffery Hall was unable to find any connection between humor and GPA scores, SAT scores, or self-perception of intelligence. Instead, being funny seems to track with extraversion and agreeable personalities, which seems to be the reason we preferentially sort for a sense of humor in partners.

“So,” you may be wondering: “is it that humans developed humor to signal extraversion and agreeableness?” We do not think so; rather, we think laughter being picked up in this way is just a happy accident that was then conveniently co-opted by our relationship-building systems.

Why Do Humans Laugh?

Sometimes we have a theory we really want to get out there in the world, and we know it’s not going to fit in any book we plan to publish in the near future, so we sneak it in somewhere kind of relevant in one of our books. This particular theory is on why humans laugh, a question which stands proudly in the realm of great mysteries in cognitive science.

There are three keys to this theory:

1. The first involves identifying when people laugh: People laugh when exposed to surprising information—or information that fits into their larger understanding of the world (or a schema presented in the context of the joke), but that still took them by surprise (perhaps it was framed differently). Basically, a laugh means: “Oh wow, that makes sense, but I didn’t expect it.”
2. The second key to this theory involves determining the stage in life during which humans laugh most: It appears that humans laugh most frequently when they are very young (from infancy to toddler age).
3. The third key to this theory entails how one feels when seeing an adult versus an infant laugh: If you have had kids, you know you have a very specific and unique positive reaction to seeing an infant or child laugh that motivates you to repeat whatever stimulus you created that caused the child to laugh.

At this point, you probably see where we are going with this. We suspect adult laughter is just an artifact of a response that is “meant” to only appear in early childhood but has been co-opted by social schema in a way that promotes group bonding. We theorize that laughter still exists to a lesser extent in most adults only because there is no strong evolutionary pressure to get rid of it (similar to crying, which probably is only meant as a communication tool for pre-verbal infants, but is still present to a lesser extent in many adults because, again, there was no evolutionary pressure to get rid of it).

When functioning properly in young children, laughter is meant to positively reinforce the provision of novel concepts by caregivers, training caregivers to stimulate children and help them learn important skills. Think of an infant laughing at a game of peekaboo: He is beginning to understand the concept that a person is still there even when their eyes are covered, but still needs some more exposure to it for it to fully “click” and is signaling this to the caregiver. This in turn causes the caregiver to want to continue playing a “game” with the child even if they don’t understand what the child is extracting from it.[[24]](#_ftn24)

Essentially, we think laughter is a bit like lactose tolerance. Up until fairly recently in our evolutionary history, only kids could drink milk without getting sick, and then the system for digesting milk essentially turned off. Only very recently did a portion of the world’s population begin to evolve the ability to keep that system operational. We suspect something similar happened with laughter just a few million years earlier.

Another use of laughter in infants could have been to bond infants to their caregivers and vice versa. If this were the case, it would make hijacking the system for mate selection especially easy as the basic “machinery” that facilitated an emotional bond based on laughter was already in place.

BUT

There are two other reasons for laughter not discussed above, and both are very relevant to human relationships in the modern age—just not in the ways you might expect:

• Sympathetic laugher: This involves laughing when you see another person laughing. Old sitcoms used laugh tracks in the background to subconsciously “trick” the audience into laughing at things that were only mildly funny.
• Nervous laughter: A lot of older research has a big blind spot: women. Women just were not used that much in older studies, meaning many of our theories on the manner in which humans react ignore responses that are more common in females. One big one is the concept of the “fight or flight” response, which is predominantly used in men when they feel threatened while the “tend and befriend” response is more common in women. Part of this tend and befriend response is to laugh when in socially uncomfortable situations or physical danger.

Why do these two other types of laughter matter in relationships? Sitcoms.

Sometimes, sitcom writers get lazy and instead of writing things that make people laugh by subverting the audience’s expectations (the kind of laughing that feels good) they would write things in a way that made people laugh by putting characters in uncomfortable, socially threatening situations and then play a laugh track over the situation to normalize laughter in response to such circumstances. This may seem like innocuous lazy writing and social manipulation, but it led many men to interpret nervous laughter the same as “real laughter,” causing them to overstep their bounds with women and feel positively emotionally rewarded for behavior women find weird, creepy, and otherwise threatening. Essentially, sitcoms have led otherwise well-meaning guys to misinterpret the “oh my God this guy is going to kill me; someone get me out of here” nervous laugh with giggly infatuation.

The Westermarck Effect & Sex with Siblings

People appear to find their relatives much hotter than other people—but only when they do not know they are their relatives. If you are separated at birth from your brother or sister, but meet them later in life, you will likely be very attracted to them. This is a bit of a problem with prolific sperm donors—there are actually online support communities for people who encounter siblings later in life that they subsequently find sexually attractive.

Given this apparent attraction, plus the strong emotional closeness we have with our siblings, why do we not want to bang our brothers and sisters when we know they are our siblings? For this saving grace, we have the Westermarck Effect to thank.

The Westermarck Effect causes people who live in close proximity in their early years to develop a sexual aversion to each other—regardless of how related they are. Simply put, anyone around you a lot in childhood, be they a step-sibling, a parent, or a biological sibling, will generate a strong sexual aversion impulse.

The Westermarck Effect has caused problems in societies with arranged marriages involving a future wife moving in with the husband’s family in early childhood. In some countries, families buy brides while the girls are still children and raise them with their future husbands, which unfortunately results in husband-wife pairs who experience a high level of aversion toward each other.

As with any sexual aversion system, the Westermarck Effect can be subject to an inverse arousal pathway, which leads one to be attracted to—rather than grossed out by—siblings. To make matters more awkward, given how strong an aversive impulse the Westermarck Effect creates, the attraction impulse generated when the sign flips is quite strong.

Roleplaying Relatives

Interestingly, many people who find the concept of sleeping with family members arousing actually still experience the Westermarck Effect and are quite repulsed by the idea of sleeping with their own family members. In such cases, either people find someone pretending to take on the social role of a fictional child, parent, or sibling of theirs arousing or they find it arousing to watch two people who are related engage sexually (see “twincest” or “wincest”). Instead of involving arousal at the idea of intercourse with actual siblings or parents, these kinks involve arousal derived from the social dynamics that these family relationships represent on a societal level.

In the case of people who are aroused by sibling porn or roleplay: Their brains may be using the sibling dynamic as a cultural shorthand for intimate trust. Through this shorthand, these individuals can quickly activate arousal pathways through either a betrayal of this trust or an indulgence in that trust depending on what emotions arouse them most.

In the case of father-daughter roleplay, which boasts a fairly large community (called “Daddy Dom / Little Girl” kinks or DDLG for short), arousal appears to stem from dominance and submission dynamics (as can be inferred from the overrepresentation of this kink in women). People are drawn to this dynamic because, in our society, dominant-submissive relationships are almost never painted in a positive, caring, and protective light—except within father-daughter relationships. The father-daughter dynamic is likely one of only a few schemas many people have that presents a warm, caring, and protective submissive relationship in which the submissive party still has autonomy.

Within the context of a society that shames almost every other type of submissive relationship, it makes sense why the daddy-daughter dynamic is so commonly seen in sexual roleplay. We also imagine a lack of respected dominant-submissive relationship schemas in which the female is dominant explains the popularity of teacher and nurse kinks among men. These social schemas represent caring-yet-dominant figures that do not challenge men’s masculinity (i.e., a person can still feel like a tough, masculine guy and be submissive to a female nurse in a roleplay situation).

The Common Practice of Marrying Cousins

While we are on the subject of incest: In cross-cultural research, the most common preferred partner is a cross-cousin marriage (one’s mother’s, brother’s child, or one’s father’s sister’s child). Among small tribes, cousin coupling reduces odds of severe inbreeding more than any other pairing.

It might seem odd that marrying a cousin might reduce inbreeding. This happens because of the Westermarck effect: When you live among a small tribe in which people occasionally cheat, about the only individual in the tribe you can be sure they didn’t cheat with is their own sibling—thus your cousins are the only people in the tribe you can be certain are not your siblings. At any rate, the risk of inbreeding drops significantly when people shift from siblings to cousins.

Keep in mind that royal families did this for centuries, and it usually took a royal family a couple of generations for inbreeding to catch up with them. According to some historical theorizing, Catholic Church laws stand behind society’s taboos around inbreeding with second cousins and other fairly distant relationships. These laws, as it happens, were most likely created to decrease power consolidation within families, which in turn boosts the church’s odds of inheriting land from the deceased. We are not sure if we believe this, but it makes for an interesting story and is backed up by the fact that, in the early 9th century, the church banned marriages with relatives as far away as 6th cousins, making finding someone to marry in a small town without an incest waver from the church VERY difficult.

Tropes

Trope attraction involves experiencing sexual arousal upon seeing someone who fits a certain type, trope, or role. Sexual stimulation derived from tropes is uniquely difficult to understand, explain, predict, and analyze. People who experience this type of attraction are uniquely attracted to a certain “type,” such as goths, punks, soldiers, teachers, biker gang members, nerds, etc.

Why would a jock guy develop a differential sexual output when looking at cybergoth girls when contrasted with girls who associate with different styles or tropes? Trope attraction is neither an evolved attraction nor one that has been influenced by straightforward socialization or conditioning (or at least we don’t see any obvious ways trope attraction could be tied to these pathways).

Some guesses:

• Perhaps people subconsciously pair tropes with desired traits in a partner, then create an attractiveness modifier in their brain.
• It could be that trope attraction is somehow tied to people one found attractive early in life (e.g., that goth girl who always sat at the front of the classroom in 10th grade biology).
• Maybe trope attraction is tied to fictional characters to whom one has grown attached.
• Perhaps the modifier that makes us more attracted to people to whom we feel emotionally close can form into amalgams if one repeatedly fantasizes about a specific type of person enough.

If you found our non-committal answer here unsatisfying and want to dig into the tropes individuals find most attractive, check out the “Arousing Dioramas” supplement chapter on page 414.

Novelty

There is an old joke about something the 30th President, Calvin Coolidge, may have said while he and the First Lady were being shown around an experimental government farm. When Mrs. Coolidge came to the chicken yard, she noticed that a rooster was mating very frequently. She asked the attendant how often that happened and was told: “Dozens of times each day.”

Mrs. Coolidge said, “Tell that to the President when he comes by.”

Upon being presented with this fact, the President asked: “Same hen every time?”

“Oh, no, Mr. President,” he was told, “a different hen every time.”

President: “Tell that to Mrs. Coolidge.”

While this story is likely apocryphal, it struck a chord with enough writers to generate a name for the dynamic it describes: The Coolidge Effect. This effect is both real and extremely pronounced in males across species and exists to some extent in females as well. When a male rat is put in a cage with a number of females, he will mate with each until he becomes exhausted, after which he will then ignore the females despite being nudged and licked. That said, the male rat will immediately become alert and begin mating again as soon as a new female is added to the cage.

The effect is present in humans, whose arousal levels quickly decline when exposed to the same arousing imagery on multiple occasions and rise when imagery is varied. Another study showed that if you expose a male to porn featuring the same actress over the course of a few days, then show him porn featuring a different actress he will ejaculate faster and release more active sperm.

This tendency does not bode well for monogamous relationships, as you might imagine. The situation is actually worse than it appears at first glance, as it is amplified by the testosterone decrease and associated libido decrease men experience when in long-term, pair-bonded relationships (this decrease in testosterone is amplified after having children, further compounding the effect). So not only do men in long-term relationships have on average lowered libido overall, but the sexual arousal men derive from seeing their partners naked will decrease.

This damper on the sexual spark of long-term relationships will be mollified to a slight extent by the increase in arousal created by any strong emotional bond created—though in the average male, this is not nearly enough to cancel out the above two effects. This is not to say that the world is devoid of men for whom these pathways are broken in some way, but in the vast majority of cases, choosing a guy or girl for a long-term relationship because you like that, during a short term relationship, they are always horny and wanting to have sex is probably a bad idea given the Coolidge Effect.

Participating in a polyamorous relationship appears to nullify the Coolidge Effect. In fact, a man who is having enjoyable sex with another, secondary female partner will report enjoying sex with his primary partner more. Having additional partners will also increase a male’s testosterone and thus their libido, so men engaging sexually with multiple partners will not only feel as though they’re having higher-quality sex with their primary partners on average but also cause them to desire more of it.

Sadly, the enhanced-enjoyment effect is reversed in females. Statistically speaking, females enjoy sex with their primary partners less if they are sleeping with other people and enjoying it. Obviously, people’s personal experiences vary, and this is just the statistical average of how the presence of additional partners affects each gender.

While many couples claim to try to mix things up through new positions and novel forms of sexual engagement, such measures are unlikely to remediate the effects of the Coolidge Effect. The Coolidge Effect appears to be triggered in part by olfactory cues (at least in rats), so it would seem that “spicing things up” outside of adding additional partners will have a limited effect.

It is hypothesized that the Coolidge Effect, or something similar, led to the evolution of traits like eye color, red hair, and freckles in humans, as such traits made their bearers appear more unique. These traits seem to evolve more frequently in populations with more females than males (often due to war and extreme conditions such as cold and high altitudes), in which there would consequently be more inter-female competition.

The Coolidge Effect is often used to talk about men, but what about women? Do women lose arousal to a partner over time as well? A 2012 study with 170 participants found that women’s levels of sexual desire declined much more quickly than men’s as relationships aged. A study of 2,100 women in 2016 showed that women who had stayed in a single relationship throughout the course of the study reported less desire, arousal, and satisfaction from sex (though we can’t help but wonder whether sex drive may be a correlating factor for women who leave relationships). Finally, two German studies in 2002 and 2006 showed that women who lived with a partner saw their desire drop dramatically over the course of 90 months—a phenomenon these studies did not observe in male participants. Despite societal stereotypes to the contrary, it looks like women may experience a Coolidge-Effect-like phenomenon that affects them even more strongly than men.

Pain & Asphyxiation

Pain and asphyxiation hijack fairly deep neural pathways—pathways deeper and more primitive than any of the arousal pathways discussed so far. Pain and sexual pleasure from physical stimulation rely on closely related neurochemical pathways that may have significant crosstalk in some individuals (with pain, it is the closeness of the neurochemical pathways that causes this crosstalk and not the spatial closeness of where it is processed like in the theorized case of feet or some social cues).

More specifically, both pleasure and pain are related to humans’ dopamine and opioid systems, which regulate neurotransmitters involved in reward pathways, causing things such as the motivation to eat, drink, and have sex. Pleasure and pain are also associated with some of the same regions of the brain: The nucleus accumbens, the pallidum, and the amygdala.

Arousal from pain is super common, with one survey showing around 44% of men and 24% of women fantasizing about spanking or whipping someone else during sex and 36% of women and 29% of men fantasizing about receiving such treatment—though it is worth reminding readers this isn’t a clear-cut activation of the pain pathway, as both spanking and whipping would activate the dominance display and submission display pathways.

In our survey, we asked: “Does this statement describe you: “I sometimes look at pornography or read romantic literature in which one of the partners appears to be in pain.” and found:

• Yes with a focus on physical pain: f20%, m15%
• Yes with a focus on emotional pain: f8%, m1%
• Yes with a focus on both physical and emotional pain: f10%, m11%

Other pain and asphyxiation related stats from our survey:

• Regularly consume erotic material that contains sadomasochism: f18% m18%
• Regularly try biting during sex: f29% m22%
• Regularly try being bitten during sex: f25% m29%
• Regularly try scratching during sex: f26% m11%
• Regularly try being scratched during sex: f19% m24%
• Aroused by being choked during sex: f26% m12%
• Aroused by choking someone during sex f10% m21%

But again, most of these survey answers are capturing arousal from dominance and submission displays that involve pain or hypoxia, rather than pain or hypoxia themselves.

As a side note: We would draw readers’ attention to how much more women are turned on by submission-related concepts than men, with 800% more women consuming erotic material that focuses on emotional pain when contrasted with men. This aligns well with what we discussed in relation to higher female arousal from submission and narrative format erotic art.

While asphyxiation does not necessarily enhance arousal through pain, it makes sense to thematically group the two. Erotic asphyxiation leverages a state of hypoxia to enhance orgasms, making them feel quite different than an orgasm obtained outside of a state of hypoxia. While this pathway is unique in that it should work for all humans, people with a strong sexual aversion to submission will likely be unable to utilize it.

Erotic asphyxiation also appears to create orgasms that are more addictive in nature and can lead to extremely destructive behavior as individuals chasing higher highs. Autoerotic asphyxiation fatalities account for about 1,540 and 3,850 each year (these numbers are from Alberta’s medical examiner, Dr. Anny Sauvageau, and are much lower than previous estimates)—though we suspect the actual number is likely much higher, as we have read it is rare to find evidence of masturbation at the scene of an autoerotic asphyxiation, so most instances of death by autoerotic asphyxiation are just reported as suicides.

From a neurological standpoint, we wonder whether pain alone, in the absence of hypoxia, can really create arousal in a person or whether pain is just a proxy for a submission display. Some have theorized that the high reported from long pain sessions during BDSM is closer to a runner’s high than a true arousal response.

We would love to see a penile plethysmograph (a measurement of blood flow to the penis to gauge sexual arousal) conducted in conditions similar to the Milgrim experiment (in which test subjects were instructed to subject others to painful electric shocks), but without the authority figure (which was present in the Milgrim experiment to order subjects to shock others) to remove other potential stimuli. With such an experiment, we could not only probe for the existence of people who are only turned on by pain, but also determine if true sadists (people turned on by causing pain outside of causing pain being a dominance ritual) exist. Alas, ethics boards would probably prevent such experiments from taking place because they are populated by killjoys more concerned with the safety of the general public than having fun.

One of the sex researchers we consulted when sanity testing this book attested to encountering those who derive sexual pleasure and excitement from pain alone; however, she never had the opportunity to ask what those people were thinking about while inflicting or experiencing that pain (those thoughts, rather than the pain, might have really been the source of arousal). She theorizes perhaps some of the pleasure derived from pain involves a feeling of release or an excuse to release.

What we can say is that when people are consuming erotic material tied to pain, it appears to be pain as a concept that is most erotic and not the idea of pain being inflicted on them or inflicting it on others. More specifically, when we asked: “When you consume material in which it appears one of the participants is in pain, where do you place yourself in that fantasy?”[[25]](#_ftn25):

• I sometimes imagine myself being the one in pain: f48%, m42%
• I sometimes imagine myself causing the pain: f27%, m58%
• I sometimes take the role of an observer: f52%, m67%

In other words, the average person who is aroused by pain finds concepts on their own to be more arousing than the manner in which these concepts relate to them personally. This implies that the majority of the people who use pain to become aroused are actually receiving arousal from the dominance/submission arousal system and not the pain system directly.

Note from the Research:

• On the topic of BDSM and pain, two studies in the Archives of Sexual Behavior found that when participants engaged in sadomasochistic acts as part of erotic play, they bonded more with their partners and developed more trust in them when contrasted with partners who did not participate in sadomasochism.

Warning: Choking Hazard

Choking during sex can act as both a dominance ritual and create hypoxia, enhancing orgasm, which is why it is such a common practice. While choking may make you and your partner feel good, you really should not do it (assuming you value your life or the life of your partner—if not . . . you do you). Sometimes you should not do things that turn you on, even if they are widely socially accepted as “not that weird” or “not that big a deal” and are fairly common turn ons.

We failed to find any method of suffocation or strangulation that can be carried out without the risk of cardiac arrest. Worse, there is no reliable way to determine when the risk of cardiac arrest becomes imminent. The probability of successfully resuscitating someone after cardiac arrest is fairly low (about 90% of people who experience cardiac arrest outside a hospital die).

You might imagine that so long as you do not take choking to a point at which you pass out, the warnings above do not apply to you. That assumption is incorrect. It is impossible to parse out the point at which unconsciousness will occur until you actually become unconscious. More importantly, unconsciousness is a symptom of other things you cannot easily identify. Stuff still goes wrong before the unconsciousness happens.

You might at this point be thinking to yourself: “No, it’s totally cool; I know this safe way of choking where you avoid the windpipe and press on the arteries that deliver blood to the brain, leading to hypoxia with no risk.” Frankly, that method is not any safer. Pressing on the carotid arteries puts pressure on the baroreceptors—known otherwise as the carotid sinus bodies. This pressure can cause vasodilation in the brain. Simultaneously, the vagus nerve sends a message to the pacemaker of your heart, telling it to decrease the force and rate of your heartbeat. While most of the time this is not that big a deal and your heart rate will just decrease by about a third, some of the time your heart rate will actually increase by three thirds and then . . . to zero as it “flatlines” into asystole. This is a uniquely difficult-to-treat form of cardiac arrest and has been documented in cases that result from as little of five seconds of this form of choking.

But then again, we drink alcohol, and we know it could kill us one day, and some fellow idiots climb Everest even though 6.5% of them will die in the process, so maybe you just like being choked enough to keep doing it despite the considerable risks and stark fact that a lot of people die engaging in this hobby on an annual basis. All we ask is that you fully, logically acknowledge the risks and do not strive to prevent such risks from being taught. This is one of the many reasons why sex education that focuses on “kinkier” sex is critical. When roughly one in four people have been chocked or choked someone during sex, we don’t get to pretend that the dangers involved in sexual asphyxiation only affect “kinky people.”

Basic Instincts

It seems as though basic instincts drive a certain amount of human arousal. We like to describe behavior driven by these instincts as “sexual autopilot mode.”

We like to chuckle at kids who smash dolls and other unwitting, inanimate victims together and say things like “Now, KISS!!” but it does seem as though physical proximity is indeed—through some basic, instinctual mechanisms—a source of arousal.

If not explicitly a source of arousal, at least close physical proximity appears to occasionally trigger something we internally refer to as “sexual autopilot mode,” which compels sexual behavior without necessarily inciting someone to feel arousal. This pathway is also seen in behavior like the dry humping instinct that some people feel when they cuddle with someone. The pathway might represent the remnant of a precognitive attraction system designed to get our ancestors to mate that only still manifests in bits and pieces within modern humans.

While this is not an easy state to study, we would be remiss not to mention that it exists as a category of attraction. This pathway may even be working off of a neurological system independent from the arousal system, as it is more of an impulse to complete an action, whereas the arousal impulse is more of a reward mechanism.

Physical Stimuli

As you are no doubt aware, when you touch erogenous zones on a person’s body, they may feel arousal and pleasure. That said, receiving sexual stimulation from touch is a little more complicated than just “touch spot X with pattern Y; sexual arousal level 2 will result.” Arousal resulting from physical stimulation is not only modified heavily by other stimuli triggering sexual impulses; these systems also work differently in different people with different levels, types, and patterns of physical engagement.

Impulses generated by physical stimulation are not always contextualized as sexual in nature. Consider the autonomous sensory meridian response—ASMR for short (look it up on YouTube if you are interested). For some people, subtle auditory and visual stimuli, such as the sound of a crinkling bag, can generate a response similar to the response triggered by light sexual touching. That said, many who experience the response do not contextualize it as sexual arousal due to the environmental stimuli that cause it to be so non-sexual in nature.

Note from the Research:

• Generally, female rats will evade their partner during sex. Some researchers theorize this to be an attempt to extend the length of sex because rat females find sex more pleasurable when it lasts longer. In some studies, graduate students are tasked with stimulating the female rats by rubbing their clitorises—and when they stop, the female rats will tug the students’ sleeves which some students interpreted as the rats “asking” for more. We’re not sure if this is relevant to humans, but we nevertheless found the behavior entertaining enough to mention after stumbling upon it while looking for info on physical stimulation, as it relates to arousal in non-human mammals.

Conditioned Responses

Pavlovian—or conditioned—sexual responses are a product of training. In one experiment, scientists were able to manufacture an arousal impulse upon exposure to pictures of boots by associating pictures of boots with images of attractive women. It is conditioning like this that most likely leads to traits like shoe kinks, seeing as we can neither find an evolutionary reason a person would find a shoe attractive nor secure evidence of any sort of neurological crosstalk that might mix up the recognition of shoes with some other arousal pathway. Furthermore, instances of female kinks around male shoes are extremely rare, which would imply that something about women’s shoes must be constantly sexualized in society, and, surprise, surprise, this is exactly what we see.

In one particularly bizarre study, researchers put some male mice in little jackets that they wore the first nine times they had sex. For their tenth sexual encounters, both the control mice and the jacket mice were randomly assigned to either wear a jacket or be in the nude. The control mice were still able to have sex in both conditions; however, some (40%) of the jacket mice had trouble in the nude condition (a similar study was conducted in which the female rats wore little jackets while having sex, which yielded the same results). Still other studies revealed we can block the kink/fetish preference using naloxone, a chemical that blocks endorphin receptors (and if it works with naloxone, it would also work with naltrexone, which is easier to get in the US).

Though this is purely anecdotal, we have observed women to be less susceptible to Pavlovian sexual conditioning than men. Consider even simple things like the smell of a perfume or cologne: When a man is exposed to a smell repeatedly in association with a pair-bonded partner, he tends to become aroused when exposed to that smell out of context or later on, whereas women seem to be more likely to develop feelings of nostalgia instead. We have seen no study that attempts to parse out if there is a gendered difference in the way Pavlovian sexual conditioning “takes” and would love to gather some experimental data on this.

Sexual conditioning is quite distinct from what some ideologies refer to as “socialization” and does not appear to function as one would expect socialization to function. In what we will call “socialization theory,” society teaches you what to find attractive. For example: If a society repeatedly contextualized women with highly-visible moles as hot, regularly featuring them in ads, socialization theory would have it that men would start to become more aroused by women with moles. This form of sexual socialization does not appear to work. You cannot teach someone what to find arousing; however, through conditioning, you can affect someone’s arousal. (We discuss evidence backing this up in the next chapter.)

Some of the historical political regimes most infamous for being effective at goading people into going against their instincts knew full well that they were better off leveraging conditioning instead of socialization. Consider the Nazis, who notably created anti-Jewish propaganda in which footage of Jewish people was interspersed with things that caused a disgust reaction, like rats, to lead people to develop an otherwise unnatural disgust toward a specific group of people.

In contrast to socialization, conditioning pairs a stimulus that triggers sexual arousal or disgust/aversion with a secondary stimulus that does not. Conditioning completes this pairing by repeatedly showing these two stimuli together. For example, advertising agencies may pair something like an attractive woman or female foot, which many already find highly sexual, with a shoe until some begin to see the shoe as sexually arousing as well.

A case exemplifying how conditioning can happen by accident in a human can be seen in a man who, as an adolescent, would hide in a small closet to masturbate and is now aroused when he sees doorknobs. Conditioning is not at play in a man whose dad insisted he needed to be tough who, as an adult, derives sexual pleasure from acting dominant. In the case of the closet masturbater, a stimulus was specifically paired with an aroused state. In the case of the man with the tough dad, he was simply told a stimuli should be paired with an aroused state. The closet masturbater illustrates a case of conditioning, which does affect arousal pathways; the dominant man illustrates a case of socialization, which doesn’t affect arousal pathways. .

Conditioning is more complicated than we imply. Few men are aroused at the sight of a computer monitor or a box of tissues, even though both are frequently associated with masturbation. We are uncertain why this is, but we assume it may have to do with rumination or the point of the arousal cycle at which the stimulus is introduced.

A separate phenomenon called sexual imprinting may or may not involve the same pathways used in conditioning. A goat raised from birth with sheep will become sexually aroused by sheep and not goats. A man exposed to a breastfeeding mother between the ages of 1.5-5 will be more likely to be attracted to breastfeeding women. In general, individuals who grew up with a younger sibling (and thus were exposed to pregnancy early in life) have a 66% increased level of attraction to pregnant women (Fun fact: “pregnant” is now the 107th most popular porn search in the United States, putting it right up there with “redhead” and “babysitter”). Another example of sexual imprinting among humans can be observed in people’s tendency to be attracted to those who resemble their opposite sex parents.

In animal studies, imprinting appears to affect different genders differently. For example, while a male sheep who imprints on goats during his formative years will never show a desire to mate with female sheep, female sheep who imprint on goats can be trained to be willing to mate with male sheep later. Basically, imprinting is irreversible for males and reversible for females.

Things That Do NOT Cause Arousal

Though we briefly dispelled common myths about arousal patterns at the beginning of the book, let’s do a second, deeper dive into arousal pathways in the popular zeitgeist that do not appear to be well supported by evidence.

Socialization

As we mentioned in our discussion on conditioning, socialization probably doesn’t stand behind a significant proportion of the population’s sexual impulses—and yet the idea that most of a person’s sexuality is “socialized” or the product of societal preferences is downright pervasive. While society can teach people what they are supposed to find arousing and aversive, we find little strong evidence suggesting that society can change people’s underlying patterns of arousal and aversion simply through instruction or inundation. You can change what a person says is arousing, but not what physiologically arouses them.

The clearest indication that socialization isn’t shaping our sexual preferences can be seen in the fact that men prefer women of healthy weights in their pornography and in their partners. Men raised in Western culture are socialized from birth to believe that rail-thin models are the ideal of beauty. From video games to billboards and television, people are taught that women at unhealthily low weights should be more arousing. Despite this, men do not prefer skinny women over women of a healthy weight in the majority of studies conducted on the subject (though in the name of full disclosure, a minority of studies do show that skinnier is always better).

In our survey, 21% of men reported consuming erotic material depicting overweight women while only 14% reported consuming erotic material featuring underweight women. This finding is supported both by extant research and the marketplace. On Alexa’s adult website list, there are (as of 2019) 504 sites dedicated to heavier women and only 182 dedicated to skinny women and three fat girl searches for every skinny girl search. The average American porn actress is in the healthy range of BMI. Only famous non-porn celebrity movie actresses regularly fall below the healthy range. This data shows that on average, men find women of healthy weights to be arousing, despite being socialized to see underweight women as ideal.

It appears that there is an average range of weights that people find most attractive in their partners and that range cannot easily be “socialized” up or down.

You may be furrowing your brow with consternation given our neglect to mention various “tribal groups” who favor fat women, plus evidence that ancient Western cultures loved fat women. You may be under the impression that these examples “prove” that cultures can socialize people into being aroused by individuals at higher body weights. Surely if the most attractive body weight in women differs widely between cultures, then socialization must be affecting arousal patterns.

The myths suggesting these cultures are common stem more from racist Victorian cultural tropes of fat-worshiping savages than real anthropology. Cultures that find fat women attractive are much rarer than those which favor forms of conscious self-mutilation, such as the use of gauges to create giant earlobes or full body tattooing. Moreover, these cultures have never been tested in a way that would enable us to determine whether people are sexually aroused by overweight partners or whether individuals within them are merely gaining societal validation from association with someone who can “afford” to become overweight.

This lack of concerted research is particularly damning given that in every single case in which a culture equates obesity with beauty that we could find, obesity was first and foremost seen as a sign of wealth. In cases in which these cultures got wealthier and were re-surveyed after this societal shift, obesity ceased to maintain its status as a good signal of wealth, and the societal predilection for fat people appears to have been unceremoniously dropped.

Consider how in modern Western societies, people would (on average) prefer a partner with a really nice car over one who rides around in a clunker. In such cases, the car does not actually turn people on; it simply signals a secondary sign of fitness (wealth). It seems that extra body weight played much the same role in some societies: People were not turned on by the extra weight; instead, they were attracted to the wealth it signaled.

As for the myth that people in Medieval Europe on average found obesity attractive: There is hardly any evidence for this outside of two painters: Peter Paul Rubens and Titian (Tiziano Vecelli). In modern terminology, these painters had what we would call a kink. Writings of their contemporaries make it quite clear that their society thought obesity was a sign of bodily weakness, which the society associated with spiritual weakness (gluttony). Some scholars attempt to argue that Rubens painted plump women in an attempt to highlight how far his society had fallen from the time of the greats, but this strikes us as a tortured argument, especially given that Rubens had a rotund wife who he seemed to find quite attractive given the fairly pornographic art he created depicting her (see: Hélène Fourment in a Fur Robe, a portrait of his second wife, or any of the pieces in which she served as a model, such as Venus, Mars and Cupid, Andromeda, or The Birth of the Milky Way). Why can’t we all just come together and say that dude was kinky, had a wife and lifestyle that enabled his kink, and spent his life in cheery pursuit of this predilection for rotund women? Even in our society, this is one of the most common kinks (as our data shows).

The only strong claim that an attraction to obesity at a cultural level was ever anything other than a predilection felt by a population’s minority comes from Venus figurines: Small figurines of obese women that date back to Paleolithic times. As we do not understand the context of these figurines, any larger associations are just conjecture. Even if these societies saw fat as a positive sign in a potential mate, it is likely because extra fat signaled wealth and abundance.

This is not to say men are never attracted to heftier women. Actually, 21% of men who responded to our study reported regularly consuming erotic content specifically containing overweight women. This suggests that the number of men in the US who consume porn depicting fat women outweighs (hehehe) the collective population of the nation’s 28 lowest-populated states. (Contrast this with only 2% of our female survey respondents who reported consuming erotic materials featuring overweight men.)

Also, while there is a range of weights men typically prefer across cultures, this range can be affected by environmental factors. Statistically speaking, the more stressed a man is, the more he receives sexual stimulation from heavier women. We would assume this is a response we evolved to search for mates with more fat reserves in times of famine. This tendency also indicates that, despite societal pressures to find skinny women more attractive, many men cannot be socialized away from finding rotund women more appealing when subject to certain conditions. You may be noticing a trend here: You cannot socialize someone to be attracted to something.

Just because socialization does not affect what turns people on does not mean socialization has no effect on sexual behavior. People may take action in their sex lives in an effort to project a certain self-image celebrated by society. That action may have nothing at all to do with arousal pathways. For example:

• A man may only date rail thin women because he believes it to be a sign of status.
• Many couples have more regular sex than they would have otherwise because they feel the need to prove their relationship isn’t dead.
• Many men seek out a high number of sexual partners merely to prove their virility to themselves.
• An individual may act as a sexual dominatrix to validate their sense of power or gain sexual partners they would not otherwise be able to secure.

This desire to fulfill certain self-images we were socialized to find valuable can skew data on sexuality.

One commonly reported attraction pattern may even be a product of self-image based socialization. Specifically, we are referring to attraction to intelligence (many surveys show people rank intelligence as one of the most attractive traits). When attraction to intelligence is a uniquely pronounced aspect of an individual’s arousal pattern, it is known as sapiosexuality. We say we suspect sapiosexuality is a product of socialization as there is no realistic pathway for the lower-order parts of our brain associated with arousal to judge a person’s intelligence. Instead, we would need to process a person’s intelligence within the higher order, “socially informed” parts of our brains, which would theoretically prompt some other, older neural pathways to receive that judgment and yield arousal.

The likelihood that some element of socialization is at play with this form of attraction does not explain its existence entirely. A similar dynamic is at play in the system that outputs arousal in relation to social status. In fact, it is possible that—depending on a person’s social context and worldview—intelligence may be synonymous with social status and that sapiosexuality is an output of this status detection system (in the same way something like vore might be an accidental proxy for the dominance and submission system).

How can we make such a controversial claim so confidently? Because despite being one of the top ten things people report to find attractive in a partner, there is no widely popular category of erotic art that targets people aroused by intelligence (outside of pornography focusing on “nerd” tropes, which would be unlikely to arouse someone genuinely turned on by intelligence in isolation).

To be clear, if true, this theory does not invalidate sapiosexuality as a sexual identity; it just implies that sapiosexuality would not appear in other cultures at equal proportions and if a sapiosexual person stopped respecting intelligence, intelligence would likely stop turning them on (which is not true for other forms of attraction, such as attraction to certain genders—if someone stops respecting men, they may still find men attractive).

Parental Screw-Ups

Stuff that happened to you as a kid does not appear to have a huge impact on arousal. In our study, we failed to find significant correlation between adult arousal patterns and childhood home conditions, family wealth, size of childhood friend groups, or family social status.[[26]](#_ftn26) Even seemingly-obvious factors, such as whether or not a person was spanked as a child, did not seem to affect whether or not spanking turned them on as an adult. We also found no connection between pre-pubescent sexual abuse and adult arousal patterns. This shocked us. For more detail, refer to the “Childhood Sexual Assault vs. Sexual Assault in Adolescence” supplement chapter on page 507.

When you ask someone (or they ask themselves) why they have an impulse that they don’t understand, their default answer is almost always going to be either “society made me do it” or “my parents screwed me up.” These answers allow someone with no understanding of how arousal pathways work to create a somewhat complicated-sounding explanation for the impulse, allowing them to feel smart. These answers are reinforced by the prevailing social schema that encourages people to create a narrative in which they are a victim with no agency. Almost everyone either wants to be a victim or hero (or in best-case scenarios, both); attributing distasteful arousal patterns to one’s upbringing makes it easy for people to play the victim.

People are extremely willing to accept the parental screw-up explanation for any arousal impulse that society considers taboo, yet they find such explanations extremely offensive for any non-taboo aspect of our sexuality. Consider how common an explanation bad parenting and “corrupting” societal influences (socialization) were for gay individuals when their sexualities were considered taboo—and yet it would be quite offensive to make such assertions today.

There is some vague cultural understanding that the socialization/parent screw-up explanation really exists to stifle exploration of the areas of our arousal patterns that we are not yet comfortable exploring as a society. As soon as society accepts an arousal pattern, the prevailing narrative swings from “my parents screwed me up” to “some people are just this way.”

This is not to say that nothing that happens to a person in childhood will have any effect on their adult sexuality—there are actually some studies showing that an effect is possible, which we will address shortly. We are merely arguing there isn’t a great evidence-backed argument to be made that one’s childhood will have a huge effect on adult arousal patterns. (To be transparent, when we first started to dig into this, we were so sure that childhood conditions lead to adult arousal patterns we wasted about half of our study on questions asking about them.)

The Myth of The Childhood Abuse Cycle

On the topic of kids getting screwed up: It is often said that people who sexually abuse children themselves were abused as children, and this creates a cycle of abuse that explains why sexual abuse of children happens. This is another one of those weird Freudian “just-so stories” that somehow captured the popular imagination. We get why people want to believe that sexual abusers are primarily a product of sexual abuse. It would be very comforting if there were a clear reason why the people who abuse children do so. It would bring hope to believe that this abuse exists in a cycle that can be broken through active efforts. Sadly, such beliefs do not appear to reflect reality. Sometimes people just randomly abuse children—sexually and otherwise.

In interviews of more than 34,000 adults in the US, it was found that around 10% experienced childhood sexual assault. If 10% of the general population was sexually assaulted and around 23% of people who sexually assault children were themselves sexually assaulted, then we can assume being sexually assaulted approximately doubles one’s probability of sexually assaulting a child. If childhood sexual abuse had no effect, the percent would be the same as it is in the general population: 10%. This suggests that while being sexually assaulted as a child almost doubles one’s odds of sexually assaulting a child later in life, the majority of people who were sexually assaulted do not assault children and the majority of sexual assaults on children are carried out by people who were not, as children, sexually assaulted themselves. (An important caveat: The stats presented here only look at male sexual abusers.)

In no way do these findings indicate a correlation between arousal resulting from the idea of assaulting a child and childhood sexual assault. These statistics merely show a connection between the behavior patterns that likely stem from the normalization of sexual assault. For information on how childhood sexual abuse affects adult arousal patterns, refer to the “Childhood Sexual Assault vs. Sexual Assault in Adolescence” supplement chapter on page 507.

We take time to call this myth out as it is wildly damaging to tell someone who was sexually abused as a child that they are now predestined to become an abuser themselves or that they are not safe to be around children as they will require enormous cognitive effort to not to sexually assault them. We hate the idea of childhood sexual abuse victims believing they caught the urge as though it were an STD or something that is so often peddled in our popular media.

Social Taboos and Rule Breaking

The concept of social taboos inherently turning people on plays out constantly across pop culture. Perhaps it is a weird hold out from the Freudian period. There is virtually no evidence suggesting that rule breaking itself is inherently arousing, yet the narrative is so easy to understand and so prevalent in our society no one thinks to challenge it. If it were true that the act of doing something taboo itself activated an arousal pathway, you would see people turned on by any social taboo at approximately equal levels (in association with how taboo the activity is). This is not seen in practice.

Perhaps we have come to assume that social taboos incite arousal because teenagers, experiencing sexuality for the first time, simultaneously experience strong drives to rebel and break rules. The teenage drive toward rebellion likely evolved to encourage people to move out of their birth tribe as well as push boundaries—it is not part of a person’s arousal pathways. At any rate, because teens are introduced to a surging desire to both rebel and have sex at the same time, people may have trouble parsing these impulses out and ultimately come to associate rebellion and boundary-pushing with sexuality.

In The Pragmatist’s Guide to Relationships, we do actually recommend getting a target partner comfortable by breaking social conventions with you before making a move. We recommend this not because breaking social conventions causes arousal, but because people tend to contextualize themselves as having a closer relationship with those with whom we feel comfortable breaking social conventions.

“Why, then,” you may wonder, “are so many kinks socially taboo?” A kink, as a concept, is literally defined by something you find arousing that is also a social taboo. Being gay used to be considered a paraphilia (the clinical term for an intense kink) in the standard diagnostic manual (DSM). Now, being gay is not considered to be a kink because it is no longer taboo—and those in our society who still see being gay as taboo likely would still offensively claim that it is a kink. Back when it was mainstream to contextualize being gay as a kink, there were actually people who claimed that the only reason people found same-gender relationships arousing was because it was a social taboo. Heck, when oral sex was less socially acceptable, one can even find mentions that the reason people enjoyed it was because it was taboo—something we now know to be absurd.

Kinks are always taboo—not because taboo things cause kinks, but because we use “taboo-ness” to define something as a kink. Continuing to attempt to explain away your sexuality with the easy just-so story of social taboos retards genuine personal exploration and your ability to predict behavior in others.

The Impact of Gender Differences on Human Sexuality

Let’s explore disproportionately male and female kinks and turn ons. Many of these differences will deeply offend, trigger, and disturb readers. Even we, as dispassionate as we try to convince ourselves we are about these things, cannot help but find some of these tendencies concerning.

Inconvenient Things that Arouse Females

The topic of gender differences in arousal patterns becomes increasingly uncomfortable the deeper you dig, so let’s get the worst of it out of the way.

First, a warning: Many people, ourselves included, have trouble with the reality that women get disproportionately turned on by some dynamics that, for lack of a better way of putting it, are not in their best interest. It is tempting to want to believe that some external source forced this on them—that they were brainwashed by society to get turned on by things that hurt them. Alas, the data does not back this up. In fact, women who report being more secure with these controversial fantasies also report higher self-esteem.

We understand why the reality the data depicts is uncomfortable. In many respects, it runs contrary to basic human logic and acts as an affront to the ideal, enlightened societies we wish to create (or believe we occupy at present).

Face it: Many things about our sexuality are suboptimal, if not outright repulsive. It is infuriating that sometimes people involuntarily become aroused and orgasm when they are raped, which only compounds the emotional pain of the experience. It is horrifying that some otherwise-good people live with shame over becoming aroused when they see their partners cry. It is sickening that some murderers get aroused by torturing their victims.

You cannot control or choose which things arouse you. That which turns you on does not say anything about what you want to happen to you or how you think the world should work. The things that create arousing sexual impulses in your brain are just the things that create arousing sexual impulses in your brain. Because you cannot consciously choose these turn ons, they say nothing about you as a person. The character of a person can only be judged by the manner in which they allow their turn ons to influence their behavior.

At any rate, let’s dig in: Many kinks that are held by females at a higher rate than males involve submission or violence. Disproportionately female arousal pathways include: Submission, getting spanked, heavy bondage, being choked, being hit, being tied up, being raped, piercing, being a slave, and cutting.

While we have touched on this a few times, it bears repeating: 53% of females taking our survey reported that a partner acting dominant in a sexual context is very arousing while only 45% reported finding the naked male form very arousing and only 48% found the sight of a penis very arousing. The “default” human female arousal pathway is not arousal from the idea of sleeping with men, but arousal from the idea of sleeping with a dominant partner and more extreme submission fantasies are seen disproportionately in females.

Anecdotally, we have observed an unusually high number of female participants in the following kink communities (given how extreme they are):

• Human doll (acting like an object)
• Public use (a fantasy of being chained up somewhere public for sex)
• Painful/forced transformation into something not human (werewolf and vampire stuff are most common)
• Petplay (dressing up like and being treated like an animal)

We would be remiss to not mention this uncomfortable gender split goes both ways. For example, men are more likely to be aroused by hitting someone than women, as well as choking someone, owning someone, etc.—but this difference is far less pronounced and prolific.

This tendency for females to be aroused by submission and violence is further backed up by online porn search data. A quarter of porn searches conducted by straight women involve searches for acts that depict male violence against women like “painful anal crying,” “public disgrace,” “extreme brutal gangbang,” “forced,” and “rape.” Women search for porn featuring violence against women at more than twice the rate of men. Dr. Seth Stephens-Davidowitz, a Google data scientist-turned-writer/lecturer, who conducted the aforementioned research, writes: “If there is a genre of porn in which violence is perpetrated against a woman, my analysis of the data shows that it almost always appeals disproportionately to women.”

Studies have also suggested that 31% to 57% of women regularly fantasize about being raped and 9% to 17% of women mark these as very frequent or their favorite fantasy experience (our data does not show numbers that high, but makes these numbers appear plausible)[[27]](#_ftn27). Heck, one of the bestselling books of all time—with a primary audience of women—was 50 Shades of Grey, an erotic novel decried by almost all mainstream BDSM communities due to its extreme and abusive eroticization of sexual violence against women.

Upon going over these stats, one of our friends told us she didn’t care what the numbers said, they couldn’t possibly be true. When we pointed out that both her own mother and sister were avid readers of the 50 Shades of Grey series, her response was: “Well, shit.” This more or less sums up how we feel about this, too.

The fact that any single woman may not exhibit these arousal patterns is irrelevant from the perspective of the larger data and understanding arousal pathways. We explore kinks that are present more often in one gender than the other to elucidate how arousal pathways develop holistically. We do not claim that all women follow this same arousal pathway.

Notes from the Research:

• A recent study showed dominant behavior is more highly correlated to mating success in males than physical attractiveness. This makes sense when you look at our research showing women on average are more aroused by dominance than the naked male form.
• Women tend to be more attracted to men who view females as pure and nurturing, but also weak and needing extra care (a concept known as benevolent sexism). That this dynamic can be displayed by a man who is not “socially backward” through historical fiction romance novels is likely a huge contributor to the success of the genre. On a similar note: The popularity of vampires in female sexual fantasies is likely due to a similar dynamic of being able to see oneself as falling prey to a man, but not because one is lesser than a human man—with the added benefit of being able to lose one’s agency through mind control, thereby being freed of responsibility for one’s total submission to a man.
• The most differential search terms used by women using Pornhub are “pussy licking” (viewed 260% more often) and “solo male” (viewed 222% more often). That said, females rarely consume erotic material through this format, so information from Pornhub is not likely to present super robust insights into female arousal patterns.

Inconvenient Things that Arouse Males

We are keeping this discussion short, as we already explored the primary dynamic at play in men’s less convenient kinks, and we don’t suspect anyone is that surprised by them. The unsavory tendencies exhibited by men reflect what our society generally expects from kinky men.

Our polls were poor at putting a magnifying glass to the gender distribution of the rarer turn ons—they’re not common enough in the general population we surveyed. Fortunately, others have done the legwork on this, specifically targeting communities with less common kinks to get an understanding of the gender breakdown in a way that wouldn’t be represented in a general population survey like ours.

One thing you often see in these other surveys is that most “inverse system” kinks (getting aroused by something a normal person would find to be gross or a turn off) are overrepresented in males. In general, males are way more likely to find things that would gross out the average person hot when contrasted with women. This means that if someone is getting turned on by being farted on, rolling around in poo, having worms poured on their face, or sleeping with a sibling—that person is likely to be male.

We talk about the evolutionary pressures that we think might have led to this gender difference in the “Breeding Targets” subchapter startingon page 70. We hypothesize that the male brain’s “software” for flipping an attraction to an aversion can change an aversion to an attraction just as easily and through the same process, and that sometimes this “code” malfunctions and flips the wrong signs (these kinks are also observed in women—just at much lower rates).

Another big difference in male and female sexuality (though not an inconvenient one—for males) is that male sexuality is much more inclusive. For example, our survey results imply that:

• 21% of men consume erotic material depicting fat women, whereas only 2% of women consume erotic material featuring fat men—though this might be a subject matter issue, as only 1% of men included fat men in their interests while 13% of women included fat women.
• 23% of males consume erotic material featuring females of low wealth while only 18% of females consume erotic material featuring males with low wealth.
• 48% of men consume erotic material featuring people much older than them while only 34% of females do the same. (Another study showed the most popular ages men search for in porn are 16 and 18, followed by 50, 40, and 60.)

It is easy to attempt to dismiss these stats by claiming that men feature a greater diversity of erotic interests in general, but our data indicates this is clearly not the case when narrative forms of erotic art (like fanfictions and romance novels) are included in the dataset.

Finally, as we touched on when talking about inconvenient female arousal patterns, males are much more likely to be aroused by scenarios that involve them hurting another person. For example, 13% of males responding to our survey reported arousal at the prospect of hitting someone while only 8% of females did, 15% of males reported feeling turned on by tying someone up while only 7% of females did, and 7% of males reported feeling aroused by the thought of actually (not role-play) raping someone, contrasted with 3% our female survey respondents.

Suppressing Inconvenient Arousal Patterns

If a person experiences inconvenient arousal patterns, surely they should just learn to suppress them . . . right?

While a person’s arousal patterns do not reflect their values, morals, or logical desires, arousal patterns are not necessarily easy to suppress. Often against our logical, moral, emotional best interests, our biology conspires against us if we try to suppress them.

Study after study shows that suppressing one’s natural sexuality has many potential negative consequences. Specifically, suppressing an impulse decreases cognitive load capacity, thus lowering intelligence. Suppressing sexual thoughts decreases general cognitive wellbeing and increases compulsive sexual behavior (likely related to the specific modality of arousal you are trying to repress, but studies don’t separate these out).

Worse, studies have identified a rebound effect tied to the suppression of sexual thoughts: Suppressing a sexual thought increases the probability of subsequent preoccupation with that thought. Nevertheless, what choice do you really have when you know something that arouses you is immoral, maladaptive, and detrimental to society?

Fortunately, such maladaptive arousal patterns can often be indulged in harmlessly through fictional content. Contrary to a popular misconception, indulging in a fantasy through pornographic material makes whatever sexual impulse that fantasy indulges easier to suppress and makes a person less likely to act on that sexual impulse in real life. We go over this in more detail later in this book’s chapter on masturbation, but suffice to say for every 10% increase in internet access in the US, there is a corresponding regional decrease of 7.3% in rapes—and when porn was made legal in the Czech Republic, rapes declined by 37% in one year with similar results seen in Denmark, Japan, China, and Hong Kong when porn was made legal in those countries.

Female vs. Male Erotic Material Preferences

One of the most striking sexuality-related gender differences is seen in the overwhelming female preference for narrative forms of erotic material. Mercifully, this gendered difference does not come with much political baggage and is generally well known.

Women taking our survey disproportionately prefer romance novels (f47% m4%), erotic young adult novels (f15% m4%), and erotic fanfiction (f17% m8%). Our survey’s male respondents differentially prefer visual representations of real people having sex, such as live action video (f53% m81%) and still photographs (f23% m59%). Note that we specify men’s differential interest in “real people having sex,” as reported consumption rates of hentai video in our survey was gender neutral (f13% m14%) (this really surprised us as we had assumed that hentai was consumed disproportionately by males).

Why is there this distinct difference in male versus female consumption of erotic material?

Some research suggests that women are more likely to encode emotions through the left amygdala, whereas men are more likely to process emotions through the right amygdala. The right amygdala enhances memory for the “big picture” of an experience, while the left amygdala enhances memory for peripheral details. This might explain the female preference for erotica and the male preference for visual pornography, as the right amygdala is more active in men viewing pornography while the left amygdala is more active in women processing erotic narratives. This could be tested were we to find men whose brains are more likely to encode with the left amygdala (vice versa for women) and see if they have a different preference in erotic material.

Our go-to hypothesis is a bit simpler. We suspect narrative-form erotic material is simply a superior method of conveying erotic content in both men and women. Men just consume it at lower rates because it is difficult to consume while actively masturbating and given the way male arousal systems work, men are likely to want to masturbate while consuming erotic content (e.g., it is hard to masturbate to the point of orgasm while reading a fanfiction, but easy to do so while watching a video or looking at a picture).

If this is interesting to you, flip to the “Erotic Material Exhibits” supplement chapter on page 409, in which we both look at the percent of females and males who consume different types of erotic material and dig into the general phenomena in more detail.

Notes for Context:

• One of the reasons the surveys we ran were able to ferret out a clearer view of arousal pathways than some past research is that it included questions about romance novels and erotic fanfiction. It is easy to look at a porn website and think: “Wow, men are into some weird shit,” while forgetting to look at a corresponding fanfiction site frequented more by women.
• We wish we could have explored in greater depth how men and women’s sexual fantasies shift in response to current events. Anecdotally, during the 2020 COVID-19 outbreak, the number of quarantine-themed erotic fanfictions (consumed primarily by female audiences) dwarfed the corresponding R34 anthropomorphized COVID-19 pornography (consumed primarily by male audiences). It’s hard to make an apples-to-apples comparison with this type of thing, but still fun to think about.

Do Men Really Have Higher Sex Drives?

The data (and we are talking about huge, cross-cultural studies of 200,000 people) makes it clear that men have much higher sex drives than women. This effect holds across cultures, meaning women’s lower sex drives are likely biological and not socialized. As with any heavily studied subject, you will find a few studies suggesting the contrary, but findings from the vast majority of studies with larger data sets align with this claim.

While the data makes it clear that women have lower sex drives on average, the data we collected also indicates that the diversity of kinks and things that cause arousal in women is no lower in women than it is in men. The average woman may not want sex as much, but is just as sexually diverse as the average man.

There has been a recent rash of authors and individuals fudging evidence in an attempt to argue that women have a higher sex drive than men. We find it bizarre that someone would want to misrepresent data merely to assert that women are hornier than men. Do those concerned with this difference equate low sex drives with disempowerment? Are their missions to somehow prove that women are super frisky carried out in an effort to empower women? This would be odd, as the belief that women’s sex drives were higher than men’s sex drives used to be a mainstream opinion in Western society—during the Victorian period, an age in which women were clearly disempowered. At this time, women were seen as dominated by their sexuality as they were supposedly more irrational and sensitive—this was such a mainstream opinion that when Freud suggested a core drive behind female self-identity, he settled on a desire to have a penis, and that somehow seemed reasonable to people. (See Sex and Suffrage in Britain by Susan Kent for more information on this.)

If the data doesn’t suggest that women have a higher sex drive, and if arguing that women have a higher sex drive doesn’t serve an ideological agenda, why are people so dead set on this idea that women are just as keen on sex—if not more—as male counterparts?

In the abovementioned study, female variability in sex drive was found to be much greater than male variability. Hidden by the claim, “men have higher sex drives in general” is the fun reality that, in general, those with the very highest sex drives are women.

To put it simply, some studies show that while the average woman has a much lower sex drive than the average man, a woman with a high sex drive has a much higher sex drive than a man with a high sex drive. Perhaps women who exist in the outlier group on this spectrum become so incensed by the normalization of the idea that women have low sex drives they feel driven to twist the facts to argue that all women have higher sex drives than men. “If I feel this high sex drive,” we imagine them reasoning, “it must mean most women secretly feel this high sex drive as well, but are socialized to hide it—I just need the data to show this to the world so they don’t have to be ashamed anymore.”

We suppose we can understand this sentiment. It would be very hard to live in a world in which few people believe that someone like you exists and people always prefer to assume that everyone is secretly like them rather than think that they are atypical.

Alternatively, the push back against the reality that women on average have a lower libido than men may just be an overreaction to an implication some people take from this—that women do not like, want, or enjoy sex. This is not true. Given how prevalent this myth is in our culture, and how it toxically suggests women are somehow deviant for enjoying sex or having sexual thoughts, we can understand the desire to fight it. We merely draw the line at blatantly spreading misinformation.

Ovulatory Shift Hypothesis

The ovulatory shift hypothesis proposes that when women are fertile, they find men with higher genetic quality (or at least men with more testosterone) to be more attractive and when women are not fertile, they prefer men who are better providers. Some recent research challenges this hypothesis, especially with short-term pairings, but by and large the consensus is that the ovulatory shift hypothesis describes a real and significant effect.

A sexual therapist with whom we have consulted on this book suggested that some women make a point of tracking their cycles and the manner in which their arousal patterns change throughout them in an effort to gain a clearer picture of their exact sexuality and understand what they really need to satisfy their sexual needs. She also said she recommended men experiment—with their partners’ consent—with providing more structure (i.e., dominance) during times of fertility. (This seems a little extreme for us, but hey, you do you.)

Here are some additional weird shifts females appear to experience as a product of their ovulatory cycles:

• It has been shown that women are more assertive when they are more fertile—perhaps to provide more protection against unwanted advances when there is a risk they might lead to pregnancy.
• Female brain volume changes in sync with hormones. Specifically, the hippocampus increases in volume (both in grey and white matter) in lock step with rising estrogen levels leading up to ovulation.
• Women’s verbal and spatial reasoning is affected by hormones associated with the menstrual cycle. The effects of this are actually quite complicated, so if you would like to dig deeper check out: “Modulation of spatial and response strategies by phase of the menstrual cycle in women tested in a virtual navigation task” in Psychoneuroendocrinology.
• Women find men more physically attractive after the men have complimented either their possessions or appearance using metaphoric language (as opposed to literal language). This effect was observed to be stronger when the compliment was given to their appearance as opposed to their possessions. Interestingly, compliments on appearance using novel metaphors were preferred by women in a relationship during the fertile phase, but by single women during the luteal phase.
• Women evaluate their relationships more negatively and their partners as less physically attractive on days just prior to ovulation. Men also perceived their partners to be less satisfied at this time. Interestingly, the study that found this did not find support for the ovulatory shift hypothesis in the classical sense.
• Women are more likely to denigrate other women when they are more fertile. Specifically, Fisher 2004 showed when a straight female is more fertile she will give lower attractiveness to other females and Karlijn Et al 2012 showed younger (and thus more fertile) women engaged in more derogatory gossip about other women.

Using Sexuality As A Looking Glass Into Our History

Now for the fun part: The “so what?” Armed with all the above information about human arousal patterns, is there anything we can tease out about the evolutionary pressures that may have created them?

The Hazards of Evolutionary Psychology and Worshipping Past Cultures

Before we explore that which our present sexuality might reveal about early human societies, bear in mind that there is nothing morally superior about historical societal structures and cultural practices. An observation that people used to own slaves is not an argument we should go back to owning slaves.

It has become rather fashionable to believe that, at some point in our distant history, things were perfect, and if we could only get back to that time, things would be perfect again. Such trendy memes are what fuel the present impression among some that the invention of agriculture was somehow the beginning of the end of humans’ quality of life—as if we would somehow be better off living more or less like troupes of chimpanzees or bonobos, foraging for food, having sex, sleeping, and dying of parasitic infections without the distinct delicacies of culture, science, technology, or the uniquely human drive to advance.

It pains us to see people suggest there is credible evidence suggesting humans lived with less daily pain and illness in the pre-agricultural period than in a developed country today. Yes, the very first people living in agricultural settlements likely had a worse diet, more diseases, and worse living conditions than their immediate predecessors—but modern humans live an almost inconceivably better life than said predecessors. Consider one of the earliest near-modern human skulls we have: Cro-Magnon 1. The dude’s face was literally eaten off by fungus to the bone while he was still alive. A female living with him lived a portion of her life with a fractured skull and her brain hanging out. The fused neck vertebrae of others in Cro-Magnon 1’s cave suggests severe injury was common in humans living during that period. Trepanning, literally drilling a hole in a living person’s skull, was such a normalized procedure during this period due to the extreme pain people lived with on a day-to-day basis that is found in 5%-10% of all stone-age skulls. We feel fairly secure in our sentiment that people who succumb to the instinct to worship past cultures are egregiously misinformed.

Beware the countless (and honestly enjoyable and entertaining) pop science books out there that cherry pick evidence and anecdotes in an attempt to argue that humans are either “naturally monogamous” or “naturally polyamorous” and proceed argue that if only people could go back to our supposedly natural monogamous / polyamorous / whatever state, the world would be a better place. These books shovel forth transparent agendas and make ultimately ridiculous arguments. Any honest look at history will reveal that those looking to create a perfect society should look into the future of our species—not its history.

Bring a critical and even mindset to any discussion of evolutionary psychology. While we adore how evolutionary psychology yields fascinating insights into how our current sexuality may have come to be and how it may work at a systems level, we dislike seeing evolutionary psychology used to justify fringe political ideologies. **Evolutionary psychology is about spinning interesting stories from scant evidence. Evolutionary psychology is for musing and entertainment. Evolutionary psychology categorically should not be the cornerstone of one’s political ideology or worldview.**

Using Kinks to Find Clues Into Early Human Cultures

Back when I (Malcolm) worked in paleoanthropology at the Smithsonian, I was accustomed to seeing researchers bemoan the fact that we could never catch a glimpse of the social structures of early human groups. Researches regret that it is hard to know which, if any, of today’s “uncontacted peoples” (primitive tribes still living in isolation and untouched by modern society and technology) have social structures similar to those of our early ancestors. Time has passed as much for uncontacted peoples as it has for us—we can only expect that they, too, would have changed dramatically.

Are we really doomed to eternal ignorance of societal structures throughout most of humanity’s evolutionary history? After all, 98%+ of the time during which our ancestors have been human-like flew by before written records began to be kept. Groups before written records produced very few artifacts revealing the clues we normally use to learn about life, social structures, and relationships.

We propose there actually are means by which we can gather some evidence of early human tribal social structures—the academic community merely has not yet considered it. All one must do is explore (surprise, surprise!) internet pornography, smutty fanfictions, and romance novels.

Kinks do not develop out of thin air. If we find that humans statistically react in a predictable but peculiar way to a stimulus, and if we are fairly certain that reaction is not socialized, we can safely guess that humans who did not exhibit that peculiar reaction had fewer surviving offspring. By determining which behaviors lead our ancestors to produce more viable offspring, we can gather clues about their cultural practices.

While all our closest relatives’ tribes (bonobos, chimps, gorillas, etc.) do have “default” social structures and mating customs into which they sort, they also deviate from these set patterns, with individual tribes featuring unique cultures. We suspect early humans were the same. An investigation of kinks and the clues they send about past societies only indicates what would have been the most prominent social structure and relationship type in human tribes. Just as is the case today, early humans were grouped into many different tribes, which no doubt formed many unique social structures. There was never a time in history during which there was a “correct way” to be human that everyone followed.

Were Early Humans Monogamous?

Did early humans have pair bonded relationships? Did they have long-term partners from whom they expected fidelity?

Questions about monogamy in early humans should be broken into two parts:

1. Were early human females expected to be faithful to a single male?

1. Were early human males expected to be faithful to a single female?

To understand why this clarification is needed, look at the default gorilla social group, in which females are expected to be faithful to a single silverback male while this single, dominant male breeds with any of the females he wants.

The testes of an animal relative to that animal’s size yield clues about the extent to which females of that species sleep with multiple partners, as males whose female partners sleep around need to produce more sperm in order to compete with the sperm of other males. Human testicles fall, on the relative size spectrum, between those of chimps (which have large testes and almost no expectation of fidelity from females) and gorillas (which have small testes and extremely strong expectations of fidelity from females).

There is also evidence from sperm morphology studies suggesting that humans produce significantly more abnormal spermatozoa in their ejaculate than chimp and bonobo males produce—but around the same amount as gorillas.

Some argue that the human male foreskin’s ability to act as a “pump” (in the sense that its shape facilitates scooping out ejaculate from a previous partner) means there was high sperm competition in our early ancestors. This is not a very strong argument, as most mammals have a similar penile sheath—even those with low sperm competition. Moreover, chimps, our closest relatives, have a very similar foreskin, suggesting it was a morphological trait our common ancestor had and our species never experienced strong evolutionary pressures to lose it. (Note: We couldn’t find whether gorillas have a penile sheath or not—and our dedication to this book’s stops were Googling pictures of shaved gorilla penises starts.)

At any rate, findings regarding testicle size and sperm morphology imply that either early human females were somewhat faithful to pair-bonded relationships or that humans were in the process of transitioning between a species without an expectation of female fidelity to a species with an expectation of female fidelity.[[28]](#_ftn28)

The fact that human males have an urge to care for the children of their pair-bonded female partners serves as fairly strong evidence suggesting that humans have historically experienced strong pair bonding with an expectation of female fidelity. There is not a single intelligent species whose males care for a specific female’s offspring to the exclusion of the tribe’s offspring without some expectation of fidelity from that particular female. While there are some species featuring males that are generally caring toward the tribe’s offspring without expecting female fidelity, there are no cases in which a male bonds to only the children of a specific female with no expectation of fidelity.

While some human tribes conceptualize children as a communal asset and responsibility, we doubt there are many who would claim that it is not in the default human mental tool kit for a father to specifically love his own children very deeply and uniquely. Just because not every culture uses a tool sculpted by evolution does not mean the tool doesn’t exist. Some cultures lack the concept of romantic love; this does not mean that humans did not evolve the capacity for love at some point under specific evolutionary pressures.

The rather unique fact that human females do not visibly signal when they are fertile presents another piece of evidence providing hints into how early human relationship structures may have worked. Most of our closest relatives signal fertility with something like an inflated red butt to show all the males that a mating during said period is likely to end in offspring. Though human female behavior is influenced by hormone fluctuations and ovulation, these effects are subtle and certainly not broadcast publicly. The fertility-signaling trait common in our closest ancestors was lost far too quickly and way too thoroughly among humans to be merely a product of disuse. There must have been fairly strong selective pressures nudging women to hide periods of time during which they were fertile.

We can think of three theories as to how a woman would have benefited from hiding her fertility (from an evolutionary perspective). The first is that early human society was a complete sexual free-for-all and, in this free-for-all, early human females traded sex for resources. In such a world, women could get more resources if males did not know whether they were fertile or not. As this theory doesn’t fit with the data from sperm and testicular morphology, we are fairly confident it can be discounted as a possibility.

Our second theory behind hidden female fertility is inspired by an interesting study on gorillas conducted by the Mondika research center in the Congo. In the group of gorillas studied by this center, females have been observed faking fertility—even when they are already pregnant—when another, lower-ranking female is in her fertile period. This indicates that human females may have shed fertility signals to both block male access to other fertile females (by keeping male partners occupied with sex with them) and frustrate other females attempting this strategy. This would suggest early humans were polygynous like gorillas. We doubt this theory, as were this the reason behind humans’ hidden female fertility, we should also see a dramatic increase in libido among women in committed relationships—which we do not see. That said, this is a very interesting sexual strategy that would probably work among humans, so we are a little surprised we haven’t seen more human females guard against infidelity by constant and frequent sexual aggression with committed male partners.

Our strongest theory explaining the lack of fertility signaling is that women experienced evolutionary pressures to trick males who are not the actual biological fathers of their children into believing that they are the biological parents of those children. This misdirection would allow women to secure resources for their children from men who make for optimal providers (think the wealthy-but-ugly man) while securing genes from men who were more genetically desirable, but perhaps less available to provide resources to offspring on an ongoing basis (think the hot guy stud who sleeps around a lot). This in turn suggests that, while there may have been an expectation of fidelity from early human females, they occasionally cheated with higher quality (from a genetic standpoint) males when they had a chance. This theory aligns with changes we see in human female arousal patterns during different stages of their ovulatory cycles.

We can argue with some confidence that humans have been “cheating” a lot and for a very, very long time. We cannot think of any other way the human female could have evolved a subconscious tendency to find lower testosterone males (with lower average genetic fitness) more attractive when they are not fertile and higher testosterone males (with higher average genetic fitness) more attractive when they are fertile.[[29]](#_ftn29)

While attraction to higher testosterone males during fertile periods in modern human women may be completely subconscious, it could not exist without women differentially being “genetically rewarded” for sleeping with one type of male over another when they were more fertile over tens of thousands of years. To put it more simply, there appears to have been a systematically rewarded behavior pattern in which a woman would convince a less genetically attractive male that he had exclusive sexual access to her and would use sex with him when she was not fertile to create a pair bond with him—while nevertheless becoming impregnated by a more genetically attractive male (likely covertly, while maintaining a resource flow from the less genetically attractive male). This is not pleasant, but we really can’t think of other realistic things that could have motivated women to find less-fit men more attractive when they were infertile.

What about males? Were male humans expected to commit to only one female, and if so, did they cheat on those females? The answer is complicated. It appears there may have been one mating pattern between 50 and 20 thousand years ago, another between 20 and 10 thousand years ago, yet another in the early agricultural period between 10 and three thousand years ago, and a final pattern between three thousand years ago and now.

We know this because of a great study: A recent bottleneck of Y chromosome diversity coincides with a global change in culture. It shows that about 4000-8000 years after the invention of agriculture, there was an extended period during which on average only one human male bred for every seventeen females that bred. While this ratio didn’t stay this extreme throughout the entire period, after looking at the data it would be very hard to argue that humans living between ten and three thousand years ago were not polygynous.

Think about it: One would really have to twist the data to explain the seventeen-to-one female-to-male breeding ratio in a society that was not polygynous. The only way we can imagine explaining this ratio without polygyny would be to argue that:

• A tribe of “Amazons” swept the globe, systematically killing most male babies during this period
• A disease arose that only killed males while leaving no archaeological trace
• Inter-tribal conflict (war) was so common—as was the use of exclusively male child soldiers—that only one in seventeen men made it to breeding age.

We don’t find these alternatives to be particularly compelling.

Research also indicates that a significantly higher portion of the female population was breeding when contrasted with the males between 20 and 10 thousand years ago, but the ratio was nothing as extreme as the ten-to-3-thousand-year-ago period. Data on the period between 50 and 20 thousand years ago suggests significantly more equity between male and female breeding rates.

If we were to extrapolate from current uncontacted tribal cultures and primate behavior to guess at what human social structures were like between 20 and 10 thousand years ago, we are probably looking at packs with a strict hierarchy run by dominant males, each with differential access to females, that are regularly attacked by outside tribal groups (more on this shortly).

When we venture back to the period between 50 and 20 thousand years ago, we really don’t know what we can reasonably deduce—it is hard for us to draw data on this period from either the genetic evidence or from modern kinks. Monogamy, polyamory, and about a thousand other systems could produce a pattern like this. We nevertheless doubt that the manner in which these earlier humans related to each other intimately would fit well within modern relationship definitions like monogamy and polyamory. There have been enough genetic bottlenecks since then that few of the behavioral impulses from this period still affect us as much as those from 20 thousand years ago to the modern period.

For the rest of this chapter, we will focus on the period 20 to 10 thousand years ago and the period 10 to three thousand years ago. At the end of the book, we will return to a focus on how the extreme polygyny of this second period transformed into the monogamous culture that is currently dominant.

The data suggesting that some form of polygyny (with a genetic bottleneck tied to it) was practiced between 10 and three thousand years ago makes a lot of sense given how humans seem to naturally sort themselves. A hefty 84.6% of unique human societies are polygynous. Yes, you read that right: 84.6% of human societies are polygynous (one man with multiple women), with only 0.3% being polyandrous (one woman matched with multiple men). Most of the rest are monogamous. Polyamorous societies are fairly rare.

We can also say with some certainty that Western society has not corrupted the data, either through the lens they are using to look at it or through colonialism, because a similar distribution can be observed in both historical anthropological sites and in travel descriptions written by pre-imperial writers in both the east and the west. When humans randomly sort themselves into small groups, more often than not those groups have a similar social structure, and that social structure is polygynous. All of our closest relatives, such as chimps, bonobos, and gorillas, also have default social structures into which they sort most of the time—even when raised in cultural isolation—so it isn’t surprising that humans would have a default social structure of their own.

If polygyny is the default human social structure, why do most people living today live in monogamous societies? In a sedentary, post-agricultural world, monogamous societies outcompete polygynous ones and thus the cultures dominating today’s political, social, and economic spheres are monogamous. Stats suggest that polygyny increases social unrest when practiced above certain population thresholds, increasing rates of rape, murder, terrorism, theft, etc. (This is not to say monogamy is the most stable model; others like polyamory have not been experimented with on a societal level, so we don’t have stats on how they would affect social vices.) We will discuss why this appears to happen in more detail at the end of the book, where we discuss how sexuality might affect the future of dating, as this recent monogamous period of human history likely had little impact on our genetics given how short it has been. For more information on this phenomenon, we recommend checking out the literature review: The puzzle of monogamous marriage.

Gender Relations of Early Humans

We have fairly strong evidence the human males that historically bred most were the most dominant in their groups and that female dominance did not affect their ability to breed as much. We can infer this from the extremely low rates of women who report gleaning sexual satisfaction from acting dominant when contrasted with males and the extremely high rate of females finding it arousing when a partner acts dominant.

You may think it axiomatic that women do not need to be dominant to breed at the same rates as males, but this is not true for all species. For example, among packs of wild dogs, only the alpha female breeds, which suggests that engaging in dominant behavior is likely a turn on for most female wild dogs, as in wild dogs, a female’s dominance profoundly affects the number of surviving offspring she has.

Humans likely sorted into polygynous structures because, unlike wild dogs in which the alpha female is the only female in a pack to breed and does so in large litters, a human female can normally have at most two children per gestational cycle (and those gestational cycles are pretty long). Tribes of humans that experimented with a dominant female who acted as the only breeder would have almost certainly been overtaken by competing tribes who allowed more women to reproduce at once and therefore gained more human capital.

Within societies in which every female—but not every male—can breed, women who expend significant energy to climb a dominance hierarchy are not going to have significantly more kids than their less ambitious and submissive peers. This puts very little evolutionary pressure on females to get turned on by acting dominant themselves while simultaneously putting significant pressure on them to identify dominance in males and find it arousing, as a more dominant male will be able to more adequately protect her offspring.

We are deeply sorry to burst the bubble of any who wanted to believe that early humans commonly formed matriarchies. While we do not doubt that at least some small tribes for limited periods of time were (and are) matriarchal; we are simply stating there is little evidence that early human societies were matriarchal. We do not take Venus figures and some early religious traditions as strong evidence for matriarchal cultures, as despite the fact that ancient Greeks had some badass female Gods like Athena and Artemis, they barely even allowed their women to talk in public.[[30]](#_ftn30) Signs of a religion focused on powerful females are not indications of gender equity in a society.

The data we collected on differential gendered arousal patterns in modern humans shows it was probably worse for ancient women than even the above picture paints.

Consider the findings from our survey:

• People who get turned on from being hit: f26% m17%
• People who get turned on by hitting someone: f8% m13%
• People who get turned on by being tied up f45% m23%
• People who tie others up during sex f7% m15%
• People who get turned on by losing agency f17% m8%
• People who get turned on by the thought of being owned by someone: f28% m10%
• People who get turned on by the thought of owning someone: f12% m15%
• People who get turned on by cutting and piercing: f4% m1%

Since we have evidence supporting our theory that socialization isn’t playing a big role in human sexuality, the gender differences in those arousal patterns must be coming from somewhere else. The picture this paints of the lives of our early human ancestors is a little terrifying.

We suspect women in these tribes lived brutal, degrading lives. Ten thousand years ago, women were likely treated like livestock. Twenty to ten thousand years ago, women likely lived within social structures in which even a low-ranking male will be treated as superior to most females (you see this pattern in chimps). The kink patterns of modern humans reveal a genetic scar from lives in which women who received arousal from being property, being hit, or being bound, survived at higher rates than men with the same arousal patterns. We say this because we cannot imagine what other evolutionary pressures could have caused these kinks to appear at such high rates in women—they are really weird, creepily specific, and present in women from an early age (so again, they are probably not socialized).

There is an alternative to a bleak history in which women were more or less treated like chattel in their day-to-day lives. Just because women who were turned on by losing agency, being owned by someone, being beaten, or being tied up had more surviving children at a rate (differential to men with the same predilections) does not necessarily mean that such selective pressures existed in women’s daily lives. Arousal upon exposure to lost agency, slavery, and bondage could have evolved as a product of repeated bottlenecks.

For example, if 30% of women in this time period experienced violent turnover at only one point in their lives due to an outside tribe or group of males coming in and killing the existing males and their offspring, that could still be enough selective pressure to create differential arousal patterns. If a portion of the females in these conquered tribes got turned on by the experience in any way, the likelihood that they survived long enough to have more children in the future would almost certainly have been higher than the women who resisted.

This theory, combined with the other data we have presented, suggests that between 20 and 10 thousand years ago, many humans lived in tribes in which one male held a dominant role, but negotiated support from subordinate males. These dominant males had access to more resources and breeding opportunities than the less dominant males. Tribes likely treated females as subordinate to males but were not egregiously violent or physically abusive toward women of their own tribe (we assume this, as this impulse doesn’t seem to exist in men today in large volumes). These tribes were either occasionally attacked by groups of roaming bachelors or other similar tribes of both males and females. We think the latter occurred, because both males and females are (roughly) equally likely to be turned on by the idea of owning someone else (f12% m15%). During these attacks, males of the attacked tribe were killed, children were killed, and females who resisted were killed.

Note from the Research:

• There is a fascinating study from Paul Sabatier University—the findings of which conflict with some of our hypothesis, but we never want to be seen as obfuscating contradictory evidence to paint a simpler picture. Specifically, male horses and female horses do not (allegedly) show statistically different behavioral patterns in terms of “moodiness,” yet it is commonly believed among horse riders that male horses are less moody, which leads them to be preferred. What is crazy cool is that we can use DNA to go back and see when humans first began to exhibit this illogical preference for male horses and through that investigation, we can get some idea of when those groups started to form certain ideas about females in general (the idea that female horses were moody came from somewhere—and it wasn’t from the horses). Specifically, despite domesticating horses 5,500 years ago, the preference for males didn’t surface until 3,900 years ago. This is around the same time that Bronze Age men became much more likely than Bronze Age women to be buried with jewelry and other valuables—a tendency (this study claims) was not observed in Neolithic burials. However, this could be an illusory pattern more indicative of the beginning of mass husbandry of horses (in such a case, female horses would stay disproportionately at “breeding centers” while the disposable males would be more likely to be seen in the possession of “customers”). (Note: Our horse friends say this study is BS, obviously motivated by politics, and conducted by people who don’t know much about horses. Apparently, riders prefer gelded horses and female horse behavior is a unique and obvious problem when they are in heat).

Chad & The Myth of the Alpha Male

Before we accidentally cultivate an obsession with dominance among our male readers, we want to highlight that a lot of misinformation is presently spread about “being alpha.” This misinformation is based on a misunderstanding of how dominance hierarchies really work in species in which multiple males are allowed to breed, such as wolves and chimps. In reality, the beefiest, strongest male is not always the alpha. The “real alpha” (with “alpha” being a colloquial term for the dominant male—the status of alpha male is not a real thing that exists in these tribes) is the male who can convince two other males, who otherwise have no chance of rising in the hierarchy, to team up with him to kill the beefy strong chimp/wolf/whatever who presently blocks their access to fertile females.

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