Why Sexual Selection Matters and Why Cordelia Fine is Wrong

Last week The Royal Society awarded the polemical writer Cordelia Fine their Science Book of the Year award for Testosterone Rex. The central thesis of the book is that behavioral differences between men and women are better explained by culture than by testosterone and that the theoretical framework that evolutionary scientists regard as the root cause of several of the robust cross-cultural sex differences we see, namely Bateman’s principle and sexual selection, have been largely debunked, at least when it comes to humans. Since this runs contrary to the broadly held consensus in evolutionary biology the choice has naturally elicited criticism from both biologists and evolutionary psychologists.

Ad Hoc Hypotheses and Occam’s Razor

In her quest to deny that biology is responsible for sex differences in behavior, Cordelia Fine has a huge advantage: she benefits from that fact (which the award has made clear) that there are certain areas of research where science doesn’t work as usual. With the academia being overwhelmingly liberal and leftist there is a clear tendency to favor certain hypotheses over others regarding the causes of human behavior. Nowhere is this more clear than when it comes to race or sex differences. That there are genetic differences between different populations or the sexes that could explain the different outcomes that we see on a societal level is simply indigestible to many academics.

To some degree this is understandable. There is no dearth of misogynist and racist Alt-Right trolls who, instead of acknowledging that huge individual variation should mean that nobody deserves to be discriminated against on the basis of gender or race, seek to end women’s suffrage and reinstate Jim Crow. One has to spend 5 minutes reading certain PUA and Alt-Right blogs to understand where reluctance to approach these topics comes from. But it would also be a mistake to give the Alt-Right a monopoly over these questions. It is better to acknowledge them and emphasize that variation within groups means no individual deserves to be discriminated against on the basis of group averages. The shock of Trump winning the presidency appears to have reinforced this already severe taboo even further. Therefore, in large parts of the academia, any biological explanation will be disregarded, at least as long as there is an alternative way to explain the data.

The problem is of course that it is easy for anyone with a little imagination to come up with alternative theories; in fact, no matter what scientific question you look at, be it climate change, evolution contra intelligent design or Einstein’s theory of relativity there is always an alternative theory that purports to explain the data. Occam’s Razor is a good principle to rely on when choosing between them. This is the idea that among competing theories the one with the fewest assumptions and ad hoc hypotheses is likely the correct one. When fossils of archaic humans are discovered creationists can always invent a rationalization (they were simply suffering from some rare deformity, or sinners punished by God or whatever) to circumvent the fact that such findings severely compromise their grand idea of Intelligent Design (which erroneously predicted that no such fossils would be found in the first place). As the wild assumptions and ad hoc hypotheses pile up to fit the incoming data it is usually discarded and the few people who still cling to the theory are ignored.

Gender blank slatism is an exception to this rule. No matter how many wild assumptions, unsupported claims or ad hoc hypotheses are needed to explain away new data and why the annoying sex differences are so stubbornly and universally persistent, the social constructionist theory still reigns supreme in the humanities and most of the social sciences. As Geoffrey Miller has observed, no gender feminist he’s ever met has been able to coherently answer the question “What empirical findings would convince you that psychological sex differences evolved?”, because no matter the finding there is always a rationalization, however unlikely, that will ensure that gender blank slatism remains unscathed. And there is nobody more prolific than Cordelia Fine when it comes to producing these rationalizations.

Most Fine’s writings are exercises in creating these so called ad hoc hypotheses. Testosterone Rex has already been critically reviewed by Jerry Coyne, Gregory Cochran, Stuart Ritchie  and Robert King, but in light of the recent award by The Royal Society I felt a thorough review of sexual selection and its biological underpinnings might be called for, just to shed light on what kind of book the world’s oldest existing science academy considers worthy of prestige.

The Role of Testosterone

It would be a lie to say the influence of testosterone on humans and other mammals is thoroughly understood. There are several complicating factors. Humans produce several hormones and there seems to be interaction between them. In addition, there are lot of bad studies with small samples and unreliable measures that Cordelia Fine, with some justice, loves to pick apart. Other confounding factors include context, individual genes and androgen sensitivity. Some men become bald because of testosterone while others do not. But that doesn’t mean there aren’t any clearly detectable patterns, especially related to the large surges that occur during certain crucial life stages such as in puberty and prenatally. Therefore, it would also be a lie to say nothing about testosterone is known. Nobody except the most deluded gender studies professor would deny, for example, that it develops muscles, deepens the voice and causes facial hair to grow. A shower of testosterone during early gestation is also responsible for shaping the reproductive organ into a penis. There is a broad consensus among biologists and neuroscientists that there are also both organizational and direct effects of testosterone on the brain, which like other human organs has androgen receptors. Since males produce much more testosterone already in utero there is also a general agreement that the hormone is involved in the development of some of the cross-cultural sex differences we see among humans.

Since testosterone and its connection with maleness is much older than the hominin line, and spans the entire mammal order, studies on both humans and animals have revealed some key details regarding how it shapes some of the pervasive behavioral sex differences we see in humans and in our closest living relatives. Similar sex differences in childhood play have been documented throughout the primate order, both among wild animals and captives. Here, males engage more in rough and tumble play and showing greater interest in objects, while females tend more towards nurturing and are more interested in infants. That the very same differences are seen among boys and girls in every culture – before they are even aware of their gender – is already a strong indication that some deeply rooted factor shared by other primates has a role to play. There is much evidence across mammal species that testosterone is a key factor in this process. Studies on animals have shown that you can alter sex typical behavior by manipulating testosterone levels during gestation. Adding a dose of testosterone to pregnant monkeys causes female offspring to play more like their male peers and masculinizes their adult sexual behavior. Patterns in humans aren’t much different, as girls with a condition called Congenital Adrenal Hyperplasia (CAH), which causes unusually high levels of prenatal testosterone, show very similar tendencies. Here, Cordelia Fine’s ad hoc hypotheses to make the social constructionist theory fit all of this unwelcome data come to the rescue.

Fine’s rationalization is that these girls are simply socialized differently because of their condition. She says the same about boys born with defect penises who were raised as girls, but this carries with it lots of unproven assumptions. Not only is there no direct evidence that they are indeed raised differently, there is very weak evidence that parenting matters much for behavior at all. That prenatal testosterone has also been found to predict more boy-typical childhood play in normally developing girls without CAH has been hand waved away by Fine for relying on amniotic fluid (one wonders if Fine would say the same had it shown the results she wanted?). Some boys in the Dominican Republic have a rare condition that causes them to be born with female genitalia and suddenly turn into men with puberty. After studying their behavior and sexual orientation the authors concluded that “the sex of rearing as female appears to have a lesser role in the presence of two masculinizing events – testosterone exposure in utero and again at puberty with the development of a male phenotype”. This takes us to another critical period which comes at puberty, when hormones start running high, especially testosterone in boys. Beginning in adolescence, and continuing into adulthood, boys all over the world start behaving more aggressively and report a stronger sex drive. In every human society men kill each other at a far higher rate than women, with similar differences seen among chimpanzees. Although this might make it seem as if human males are wild beasts it is important to remember that although the sex difference in homicide is large, most men will never commit a murder during their lifetime, and when they do it’s mostly other men who are the victims.

When female-to-male transsexuals undergo hormone replacement therapy they report analogous behavioral changes. Reading personal stories of trans men describing the effects of testosterone on their libido will make anyone who has ever been a teenage male empathize. Trans women report very different experiences. After being administered testosterone trans men also show an increase in violent and criminal behavior, and there are similar effects in animals. The peaceful bonobo males are often invoked in this case, but they are unique among male apes not only by showing no clear symptoms of Young Male Syndrome but also by lacking the pubertal testosterone surge of their more macho cousins. At times Fine seems to suggest that while differences between trans men and cisgendered women might be caused by hormones, the differences between men and women are not, because women’s brains (while at the same time apparently being identical to men’s) could be more sensitive to the effects of testosterone. But this rhymes badly with the fact that genetic males with complete androgen insensitivity are so behaviorally similar to most other women that their condition is very seldom discovered before puberty and sometimes not until long into adulthood. I guess you all see now where this is going?

Bateman’s Principle and Sexual Selection

Fine’s silly mathematical exercise to dismiss Bateman’s principle, namely higher male variance in reproductive success, has been dissected by several other reviewers already so further comments aren’t really needed. Likewise her efforts to debunk a single experiment from 1948 while ignoring tons of research showing the same results. The evidence that this basic foundation of sexual selection holds up is so overwhelming at this point, no matter if you look at humans or at the animal world, it is incomprehensible how anyone could still deny it with a straight face. Genetic evidence show a few extremely successful men have millions of descendants today. All of this is a result of the fact that across species, males tend to invest less in reproduction, and therefore are less choosy and compete more intensely for mates. The differences in muscle mass and physical strength between men and women reflect this evolutionary history.

What is interesting is seeing Fine’s attempts to explain away the predicted outcomes of sexual selection, such as men’s greater tendency towards promiscuity, with similar ad hoc rationalizations as she uses to explains away the role of testosterone. In Testosterone Rex Fine spends a lot of time criticizing the famous Hatfield and Clark study in which confederates randomly asked peers of the opposite sex if they wanted to have sex with them. As opposed to the women, none of whom answered yes, most of the men seemed happy to sleep with a person they’d just met. This experiment has since been replicated with similar results.

Seemingly incredulous that so many young men answered “yes” to the offer of sex with an attractive female stranger Fine first suggests the men were only joking. More convincing is her argument that women were afraid to be alone with a stranger – who, being male, was probably much stronger. But this can hardly explain why the difference persists among homosexuals. An Australian study from 2014 showed that while lesbians and bisexual women reported an average of 6 same-sex partners, gay and bisexual men averaged 96 of them. This is not to say women will never say yes to casual sex, just that they are more choosy about with whom, precisely as Bateman’s principle and Robert Trivers’ theory of Parental Investment predicts.

The studies often cited by Fine and others do not contradict the overwhelming evidence when you take a closer look at the data. There are of course instances where females can be very promiscuous such as to avoid infanticide by confusing paternity. This happens in our closest relatives, chimpanzees and bonobos, which is reflected in the testes size and sperm quality of male chimps. But females are choosier than the males even among chimpanzees  and bonobos, just as sexual selection theory would once again predict. Cordelia Fine mentions some species where these roles are reversed but such species, characterized by higher male investment in reproduction, confirm both Trivers’ parental investment theory and Bateman’s principle rather than contradicting them. While culture certainly matters this difference persists even in modern egalitarian societies and Fine might be surprised to know there is little evidence that men are the main enforcers of conservative sexual mores. Even less convincing are her repeated appeals to the crisis-ridden field of social psychology and its non-replicable findings such as priming, implicit bias and the stereotype threat.

Her arguments are also somewhat self-contradictory, after arguing for pages why Bateman’s principle doesn’t hold up and that women are as promiscuous as men, she dismisses the likelihood of evolved male promiscuity in humans with the argument: “the theoretical possibility that a male could produce dozens of offspring if he mated with dozens of females is of little consequence if, in reality, there are few females available to fertilize, and competition for them is intense”. But if women were as promiscuous as men most men would probably have little problem achieving that as evidenced by the average number of sex partners for gay men. It simply doesn’t prove that straight men wouldn’t do that if they only could and the fact that more attractive men have more casual sex partners but no such correlation is found with women indicates that a lot of men really would like to be more promiscuous. As we have already seen, those few men in ancient times who could have a lot of partners did leave a lot of descendants, which means that such traits have been selected for in men. Looking at sex ratios it seems men become more promiscuous when there are lots of potential mates, which doesn’t seem to be the case with women. This is not to say that every single man is inherently promiscuous and incapable of monogamy, or the reverse for women – and fading hormone levels also make the sexes become more similar with age – but the overall pattern is quite clear.

Another prediction from sexual selection that Fine tackles is the area of risk-taking, where she questions the notion that women are generally more risk-averse than men. If males vary more in reproductive outcome they are expected to take more gambles since the prospective pay-offs are far higher. As Cochran and others have pointed out she tries to obfuscate this by pretending that what we define as risk-taking is in essence entirely subjective. While walking on a tightrope 2 feet above the ground might result in a scraped knee, doing the same at 100 feet might result in death. This leaves little doubt in most people’s minds about which option is the more risky one. In her book she wonders whether the reported sex differences would remain if the questionnaires included questions such as “How likely is it that you would bake an impressive but difficult soufflé for an important dinner party?” (yes, this is a direct quote). While taking on such a responsibility might result in social embarrassment and a missed promotion, the possible consequences are far more dire in the heavily male-dominated sport of base-jumping. Looking at injuries and mortality rates by sex worldwide might give Fine pause for thought.

Why Not All Men are Taller than All Women

Fine can be disingenuous in her argumentation, which can be frustrating to her critics many of whom have rightly drawn attention to this. A common trick, especially when she is under pressure, is to simply say that the differences are not categorical or absolute and depend on various factors. She often emphasizes that men have no monopoly on promiscuity or risk-taking, seemingly unaware that researchers who study sexual selection would never object to such a statement. But men have no monopoly on being 6 feet tall either and yet nobody can deny that men are generally taller than women. If the differences were categorical rather than distributional there wouldn’t be a need for women’s prisons but despite the fact that the majority of men don’t commit violent crime there are women who do (albeit far less often). There will always be variation because sex is not the only variable, the point is, that because of sexual selection, sex will be one important variable for many traits. Sex is not even the only biological variable since individual autosomal genes of course matter as well. This will create distributions of these traits rather than categorical differences but because of these distributions it will be impossible to erase all average differences and create a gender neutral society without totalitarian measures. If sex wasn’t a variable, ecological factors, such as an abundance of mates, wouldn’t affect the sexes differently which is what we see when looking at sex ratios. In short, enforcing rigid gender roles or erasing gender differences altogether would both lead to oppression, in a free society you will see men and women everywhere but the distributions will differ.

Instead of stressing that differently skewed distributions is no reason to stop treating people as individuals Cordelia Fine, in media interviews and throughout her book, can’t stop dreaming of a cultural revolution to reach her utopian egalitarian society and she gives the impression she is prepared to be radical to achieve that goal. One person who has fallen hook, line and sinker for Cordelia Fine’s rhetorical sophistry is The Royal Society jury member Sam Gilbert who defends the decision to award the book by arguing that Cordelia Fine recognizes that Bateman’s principle in humans is valid in “certain ecological, social, and economic conditions”. This totally misses the point, since nobody has argued that ecological conditions don’t matter. What matters is that sex is one important variable and in humans as well as in most other mammals it is important enough to create certain behavioral patterns that you see, sometimes to a higher or lesser degree, in every society in the world. With humans becoming less polygynous and more monogamous over time there is a discussion about exactly how large these differences are but to deny their existence is to engage in flat out science denial.

What Does Testosterone Rex Really Say?

If Sam Gilbert and his fellow jury members keep insisting that Testosterone Rex is a deserving winner for accurately pointing out that sex differences aren’t categorical and that ecological conditions matter as well, which seems to be the motivation, it is strange that they decided to award a book that does such an abysmal job at communicating that message. She describes the foundations of sexual selection theory and Bateman’s principle as being in a state of turmoil when the truth is that the evidence is stronger than ever before. Reviews in the press make it clear that lay people reading this book are left with the impression that testosterone doesn’t really matter and that sexual selection is a myth. Why award Cordelia Fine with a prize that is intended to reward the best science writing for a non-specialist audience if the non-specialist audience misunderstood what Fine was trying to communicate? Not to mention that her use of ad hoc hypotheses, based on unproven assumptions, to explain away well-established science are analogous to the favorite tactics of the proponents of intelligent design. If the Royal Society recognizes that sexual selection and testosterone is relevant for human behavior their choice couldn’t have been more mistaken. The most likely explanation is that the choice is based on the erroneous idea that fighting sex discrimination requires pretending that average sex differences do not exist. The only remaining alternative, that the world’s oldest science academy has abandoned Charles Darwin for pseudoscientific gender theory by virtue of sincere belief, is just too depressing to even consider.

Update 2017/09/29: Thanks to Ben Sixsmith for proofreading and improving the grammar!


19 thoughts on “Why Sexual Selection Matters and Why Cordelia Fine is Wrong

  1. Yeyo: I don’t have a twitter account but read your feed avidly. Thanks for writing this. I will use this comment section as a way to ask you questions!


  2. Hello Mr Yeyo, big fan of your Twitter.

    I wanted to bring something to your attention, via a study linked originally by Scott Alexander of Slate Star Codex. The abstract states that:

    “Females with CAH had more interest in Things versus People than did unaffected females, and variations among females with CAH reflected variations in their degree of androgen exposure.”

    Assuming that there’s really a solid level of correlation, that’s a powerful argument.Now that I look harder, maybe they only hypothesized it though:

    “Moreover, scores of females with CAH on interest in Things-People were hypothesized to be correlated with their degree of prenatal androgen exposure.”

    Anyways, here’s the study itself; I’m a busy guy (and a lazy one), but I hope this can be of use to you. And if it is, I hope it can enter the discourse and beat down a few lazy feminist arguments. Cheers!



    1. They put it to test and the results confirmed the hypothesis, just look at the study. In the final part authors conclude the following:

      “The results support the hypothesis that sex differences in occupational interests are due, in part, to prenatal androgen influences on differential orientation to objects versus people. Compared to unaffected females, females with CAH reported more interest in occupations related to Things versus People, and relative positioning on this interest dimension was substantially related to amount of prenatal androgen exposure.”


  3. Thank you Yeyo, your argumentation is excellent and your criticisms are backed by sound evidence and strong logic. We need a lot more of this kind of article to keep a strong voice against gender fetishism, and of course against sloppy applications of or denials of science.


  4. Good article. Just a side issue (irrelevant to your argument): in your introduction you conflate Creationism and Intelligent Design. They are different, if not contradictory, things.


  5. Very good read, thank you. A tiny question, when you wrote ” … annoying sex differences are so stubbornly persistent (even in countries who desperately try to engineer them away)…”, did you have, in the parantheses, Sweden in mind? Sweden in a secular state where the 50-50 ideology has replaced the role of the religion.


  6. “Testosterone Rex” is such great title for a book. I almost bought it on that basis! Now I’ll probably skip it — too many books with a more reliably scientific method to read. Including by Geoffrey Miller, whom you cite.

    Able review; much appreciated.


  7. Jerry Coyne has suggested that Sam Gilbert (the only neuroscientist on the judging panel) should probably have recused himself as he likely knew Fine from their time as PhD students together at UCL.

    UCL is a very large university – but Gilbert and Fine were both PhD students in the Institute of Cognitive Neuroscience based in the same small building on Queen Square.

    With very similar phone numbers back then, they may even have been in adjacent offices…




  8. Truly depressing. It seems reminiscent of when the Soviets distorted science to match their ideological preferences. Dreadful. She must know she’s being deceitful.


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