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Cordelia Fine’s “Testosterone Rex” — A Review

A review of Testosterone Rex, by Cordelia Fine. W.W. Norton and Company (January 2017) 272 pages. 

“Scientism”. “Orientalism”. “Historicism”. The trouble with inventing a belief system and ascribing it to your opponents is that you might inadvertently have built a straw man. After all, nobody actively signs up to these supposed philosophies: they’re terms of criticism or abuse. One such nebulous belief system is the topic of psychologist Cordelia Fine’s new book, Testosterone Rex. Unconcerned by the straw-manning risk, Fine introduces the eponymous “Testosterone Rex” as the “story of sex and society” that holds that there are male brains and there are female brains, programmed by evolution to be irreconcilably different, with testosterone explaining males’ greater risk-taking, promiscuity, competitiveness, and dominance. Fine argues that modern science is the asteroid that wiped out this T-Rex, revealing subtler cultural—not biological—explanations for the sex differences we see in society.

Fine’s first target is the ‘Bateman Gradient’, a seminal (excuse the pun) finding on sexual selection from 1940s experiments on fruit flies. Geneticist Angus Bateman found that the link between number of mates and reproductive success was stronger (the ‘gradient’ steeper) for male than for female flies, and theorised that it’s more important, evolutionarily speaking, for males of any species to be promiscuous, competing for mates. Females, on the other hand, have to put a lot more resources into producing eggs (costly compared to sperm), as well as gestating and caring for offspring, and so should pick their mates more carefully.

Fine points to the fruit fly experiments—and later theoretical elaborations by Robert Trivers—as the origin of damaging stereotypes about wanton males and picky females. As she explains, statistical and methodological flaws were found in the original study, and in subsequent decades biologists have discovered species where there’s no male-leaning Bateman Gradient. An anonymous biologist tells Fine that the original Bateman and Trivers work is only cited these days “for sentimental reasons” (though I found that the 1972 Trivers paper has been cited 642 times since January 2016 – that’s an awful lot of sentiment).

All this has been a genuine debate in evolutionary biology, but Fine’s summary is partisan. A 2016 meta-analysis—a systematic research review—confirmed the idea that, across the animal kingdom, sexual selection is generally stronger for males. Perhaps this review appeared too late for Fine to cite, but it does rather puncture her picture of “a state of turmoil” in the science of sexual selection. On the contrary, Bateman’s theories seem to hold up pretty well.

So much for the fumbled discussion of animals in general. What about humans in particular? Fine makes great sport of a statement from psychologist David Schmitt, who wrote that “one man can produce as many as 100 offspring by indiscriminately mating with 100 women in a given year”, implying that “men’s mating strategies [should] favour at least some desire for sexual variety”. This logic provides part of the explanation for more promiscuous males. How silly, argues Fine. She calculates that the probability of this hundred-baby strategy working would be around 3.63×10-156 (a very small number indeed). The problem is that this is a fairly outrageous quote mine of Schmitt, who in the very next sentence explained that the strategy would “rarely, if ever, produce 100 offspring”, arguing that what matters is that males who adopt the strategy will tend, on average, to have more children than will women. It’s the Bateman Gradient again, and there is convincing evidence that it is found in humans. In what one might call an ‘interesting’ scholarly tactic, Fine sheepishly alludes to Schmitt’s full argument in an endnote referenced three pages after the original partial quotation.

This fits into a pattern: evidence contrary to Fine’s position is often cited, but it’s not mentioned in the text, instead being relegated to endnotes where it can’t cause too much trouble. Witness, for instance, Fine’s mention of “stereotype threat”, where a single supporting study is discussed in the text but a contrary meta-analysis is only mentioned in the endnote. Or her discussion of a 2015 paper on how males’ and females’ brains aren’t essentially different, but are a mosaic of features: you wouldn’t know that four strong scientific critiques of the study had been published (with a response) unless you flick to the back of the book. This allows Fine to use the main text to critique only the most overblown claims about sex differences, and avoid having to deal at length with more reasonable arguments.

Admittedly, Fine does deal effectively with those overblown claims. Her chapter on testosterone itself is a useful pushback against assertions about the ubiquity and power of a molecule whose behavioural effects are not well-understood. But for all her stinging critiques of “Testosterone Rex” research, Fine is far more magnanimous—often completely silent—about the weaknesses of the research that supports her view. For instance, in response to self-reported studies of numbers of sexual partners, which are subject to expectancy bias (they might over-report male promiscuity), Fine cites an interview study of 50 men who frequent prostitutes, apparently not realising that such qualitative research is far more vulnerable to the same kind of bias. The final chapter speculates heavily about the idea that “gendered” toys (blue versus pink; cars versus dolls) have effects on girls’ career choices, uncritically citing weak studies (for instance this one, which included only 62 children). The harshest Fine gets about a sympathetic paper is when she discusses a ropey-looking social-priming study on men’s “threatened masculinity”, finishing with the bland statement that “we have to be careful that findings like these are robust and replicable”.

Given all the above, you might be surprised to read the following paragraph from Fine:

To be very clear, the point is not that the brain is asexual, or that we shouldn’t study sex effects in the brain… genetic and hormonal differences between the sexes can influence brain development and function at every level… [I]nvestigating and understanding these processes may be especially critical for understanding why one sex can be more vulnerable than the other to certain pathologies of brain or mind.

Absolutely! Autism, Alzheimer’s, depression and other conditions have very skewed male:female ratios—a primary reason neuroscientists are interested in sex differences. How odd, then, that Fine ends the paragraph by saying: “The point is rather that, potentially, even quite marked sex differences in the brain may have little consequence for behaviour”. True, this contains a “potentially” and a “quite” and a “may”, but it’s a strange conclusion. Unless you’re a dualist who thinks that behavioural differences—such as the reliable sex differences in physical aggression or spatial ability—are manifest somewhere other than the brain (and unless you think pathologies don’t lead to behavioural differences), the same logic Fine is happy to use for pathology applies just as much to behaviour.

In the end, Testosterone Rex is a curate’s egg (or perhaps, given the topic, a curate’s egg-and-sperm). It’s a semi-straw man, successfully debunking the most extreme and simple-minded claims about sex differences, but giving a terribly one-sided view of the science. If you’re a dinosaur who thinks men and women are completely different species, or that testosterone is the only reason sex differences exist, the book might be a useful corrective. Anyone with an even slightly more nuanced view should look elsewhere.


Stuart Ritchie is a Postdoctoral Fellow in the Psychology Department at The University of Edinburgh. Follow him on Twitter @StuartJRitchie.

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  1. John says

    I’d be interested to know the male:female ratio of antagonists to genetic explanations of behaviour differences between the sexes. From anecdotal evidence it seems to me to be more supported by women. If so, and assuming not-in-the-genes proponents have some kind of bias (i.e. the science as indicated in this article is correct, which I believe to be true), why does a not-in-the-genes bias appeal more to women? Speculations anyone?

    • Jalfrezi says

      Women know they’re innately inferior but want to blame their shortcomings on society.

    • Mars says

      Explanation should be relatively obvious. Women have throughout history been regarded as less capable and are to some degree still today. So obviously they don’t like the notion that there are meaningful psychological sex differences as those might be used to conclude the historic view is correct

      • Mars says

        a few characteristics men might also not like being ascribed to them as innate characteristics such as being more violent, but it’s more for women

    • John Fabian says

      I imagine it has to do with feminism. Women– for obvious reasons– are far more likely to be ideological feminists. If there are congenital average differences between men and women, and those differences are significant enough to affect organic development of social structures, then the edifice of feminist analysis falls apart. So, the feminist is ideologically motivated (probably on a sub-conscious level) to reject such explanations.

      • John says

        @JohnFabian “If there are congenital average differences between men and women, and those differences are significant enough to affect organic development of social structures…”

        Let’s say that’s true. Then a valid feminist stance would be to counteract those effects such that the organic development does not favour men. Rather than to deny the science. No? Otherwise you’re assuming that those average differences mean men are (statistically speaking) better endowed. It may be that whatever (average) differences exist are spread evenly between men and women (i.e. men get a statistical bump in one capability, whilst women get a compensatory bump in another). Personally I can imagine that women are actually, statistically, “better endowed”, but that might leave them worse off in an “organic development of social structures”. To take one personality trait, for a bit of a trite example; perhaps men are statistically more (congenitally) prone to value status more, and that motivation leads to more men than women in boardrooms. The answer to this would not be to deny the fact of the matter, but to expose that truth and perhaps devise compensatory structures and to educate folk about the evidence for it in order to defuse that tendency.

        But I buy your summary of “ideologically motivated (probably on a sub-conscious level) to reject such explanations”. I’m just not sure about the path to the ideological motivation.

        • Yeah Nope says

          @John “Then a valid feminist stance would be to counteract those effects such that the organic development does not favour men.”

          You mean social, cultural, political,and legal systems that are absurdly biased in favor of women? Like the family court system, criminal court system, women only (group x), political advocacy groups, levels of social funding, gender quotas. Or perhaps campaigns to normalize derogatory terms such as “toxic masculinity”, or campaigns to make derogatory normal terms such as “straight white male”, or to pathologize typical masculine traits such as stoicism, dominance, competitiveness, and aggression.

          “Rather than to deny the science.”
          As you see above, feminists are fully engaged in “counteracting those effects”, generally not to raise women up, but to push men down. And to slightly adjust the quote from the Old El Paso commercial “Why can’t they do both?”. Manipulating biases and denialism of biology go hand in hand, and none are better at it than feminists.

    • Yeah Nope says

      “why does a not-in-the-genes bias appeal more to women?”

      What’s easier to accept for demographic that is constantly told that sexism is rampant:
      1) Women have been oppressed by men since the dawn of humanity.
      2) Both physically and mentally women score lower in nearly every measurable metric, and without modern technology the very idea of gender equality, as defined by feminism, couldn’t exist.

      The first, which is the stance of feminist ideology, allows women to blame everything on an external force, and therefore shift responsibility for corrective measures onto that external force.

      The second requires women accept that their very biology puts them at a disadvantage to men, and it’s the technologies created by those very men that partially masks those disadvantages, allowing women to flourish in ways that have never before been possible.

  2. Thursday says

    I haven’t read the new book, but Fine had some batty things to say about girls with CAH, who don’t exhibit female typical behavior, in Delusions of Gender.

    Let’s say that CAH girls really are socialized differently. That would mean that sexist societies don’t actually socialize all girls to act girly(!), but (for reasons that are never explained) somehow pick up on the rather subtle cues (what these are is, again, never explained, at least that I recall) that distinguish CAH girls (and, remember, these can’t be behavioral tendencies resulting from CAH) and then they then socialize these girls to become more boy-like. Seriously, WTF?

    • Sashank Sriram says

      She didn’t say that CAH girls are socialised differently. She compared the behaviours of a certain species of monkeys in two different places in Japan and talked about a conclusion that somehow testosterone seemed to shape the brain according to the society too. The way it is, seems logical, although we don’t know yet if it’s scientifically true. But, she did explain the reason. I suggest you go through that part one more time. Her Delusions of Gender is near perfect, it’s only her Testosterone Rex which contains some ideological loopholes.

  3. Harriet says

    You can’t glorify female typical traits without sounding like a patronising traditionalist. It is so much easier to glorify male typical traits but when you think about it, the cultures that only glorify male typical traits are often the most hostile and brutal to women.

  4. Santoculto says

    What hdds still don’t understand is that gender is ALSO a social construct ’cause culture-co-evolution,


  5. mike says

    Men and women are different. They’re genes are different. Their brains are different.

    So effing what?

    They’re more the same than different.

    Thanks for the review.

  6. Good article. But it begins by implying that scientism isn’t a real ideology that anyone actually believes, just something that’s invented for critics to knock down. I beg to differ. How does Daniel Dennett fail to qualify as an adherent to scientism?

    • yandoodan says

      Scientism is the treatment of Science as an ontology rather than an epistemology. No one who understands this (or even the words) would possibly admit to believing it. Indeed, no one who doesn’t understand this would admit to believing it; it’s stupid. But it’s also common. We need a name for it.

      • David Mathers says

        ‘Scientism is the treatment of Science as an ontology rather than an epistemology.’

        Insofar as I understand what this means, I can tell you that no one believes that science is ontology instead of epistemology, but many philosophers would like to derive both their epistemology and their ontology from science.

        Or, in layman’s terms, that are designed to help people understand who aren’t familiar with the jargon rather than show off: no one thinks science is an account of what sort of things there are rather than a method for finding out about the world, but lots of people want to both say that science is the best way to know the world and that it gives us lots of information about what stuff there is (for example, that there are electrons.) Of course, theories often turn out to be wrong in the long run (i.e. there wasn’t really phlogiston or an luminiferous aether). But that’s got nothing to do with the distinction between accounts of knowledge and accounts of what there is. (And the people accused of scientism and those who want to ironically reclaim the term don’t generally think that *current* science will turn to be right about absolutely everything.)

    • Luke Reeshus says

      Good article. But it begins by implying that scientism isn’t a real ideology that anyone actually believes, just something that’s invented for critics to knock down. I beg to differ.

      I’ve never seen anyone use the term “scientism” in a rigorous way, as pointing to a specific ideology that people actually believe. It is always used as a pejorative word, and an incoherent one at that–usually by people who think certain domains of the human condition are off-limits to science, or who reject the unity of knowledge for ideological reasons.

      For instance, those who believe evolutionary biology can inform our ethical reasoning are often accused of scientism, and their detractors usually recruit David Hume to take them down. This is ironic, because Hume was trying to ground ethics in facts of nature, not declare them utterly separate. But no matter.

      Speaking about facts of nature, and to address yandoodan’s point, no one (at least no one reasoning clearly) thinks of science as an ontological position. Rather, their ontological position is naturalistic (or materialistic), and this is what people who accuse them of scientism are usually taking exception to. I’d bet this is the root of your problem with Dan Dennett, because he thinks that consciousness, however mysterious, is a natural phenomenon–a position most people recoil from, for obvious reasons.

      To return to the link between science and ethics, I’ll tie this off with a few words from the infamous “scientisist” Steven Pinker:

      “The facts of science, by exposing the absence of purpose in the laws governing the universe, force us to take responsibility for the welfare of ourselves, our species, and our planet. For the same reason, they undercut any moral or political system based on mystical forces, quests, destinies, dialectics, struggles, or messianic ages. And in combination with a few unexceptionable convictions— that all of us value our own welfare and that we are social beings who impinge on each other and can negotiate codes of conduct—the scientific facts militate toward a defensible morality, namely adhering to principles that maximize the flourishing of humans and other sentient beings. This humanism, which is inextricable from a scientific understanding of the world, is becoming the de facto morality of modern democracies, international organizations, and liberalizing religions, and its unfulfilled promises define the moral imperatives we face today.”

      • David Mathers says

        Fun fact, Pinker gave a positive dust jacket quote for Dave Chalmers’ famous attack on materialism in The Conscious Mind, and if I recall rightly, subscribes to a most un-Dennettian view that consciousness is a deep and perhaps unsolvable mystery. (I’m more sympathetic to Dennett’s view.)

    • strongforce says

      “Is social constructivism itself a social construct?” Of course it is

  7. You can simply say that all people should be allowed to proceed according to their own inclinations and talents and be done with it – except – when people look at men or women or white or black statistically – in the mass – then the arguments begin as to why there are more men doing this and fewer blacks doing that… then one comes under pressure to know the unknowable in a big hurry.

  8. janskzz says

    I noticed in Cochran’s review he said: “Testosterone is a strawman theory, here. Sex differences might be caused, in part or in whole, by biological factors other than testosterone” What are the most likely hypotheses for what causes biological sex differences other than testosterone? How does the Organizational-Activational Hypothesis stand?

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  10. Sashank Sriram says

    I actually liked Delusions of Gender. It was a real scientific piece of marvel, and debunked all myths we find today, in it’s three parts. But I expected more from her, for her experiences in research. For example, though she debunked thousands of faulty studies, she cared less to actually review what neuroscience has to say about sex differences. The potential arguments for cognitive differences in sexes, namely differences in corpus callosum, white-grey matter ratios, sizes of hippocampus and hypothalamus, etc. are largely dependent on brain size, and consequently, on the size of men and women. So, sex differences in, for example, spatial skills, is probably a direct consequence of the size of people. Next, she should have focused more on how the structure of brain changes due to the social environment, but she stopped with only the social environment argument, focusing less one how, though brains can be at a cognitive disadvantage, learning tasks can make it alright. For example, it has been shown that women match men when learning a spatial skill, so if fMRI scans should be taken, that should be enough to establish the fact that however disadvantaged male or female brains are, practice makes them perfect. Rather, her Delusions of Gender seemed more focused at highlighting sexism and bias in the workplace and parental gender bias, which were all good and true by the way. Had more about neuroplasticity and how it can change the brains, and its potential to erase behavioural differences between the sexes (that might have a biological basis, but roots mostly seem to lie on social environment and sex differences in height and weight) been discussed, this book would have made a good neuropsychology textbook on gender.

    But Testosterone Rex was disappointing. Not just because of Angus Bateman or other weak researches (Though I’d have to admit that it really disappointed me and my view of Cordelia Fine as an upright perfectionist myth-buster became blurred). Though her myth-busting needs commendable appreciation, her book still failed to actually look into what promiscuity means and what not. Now, she could have gone through the following argument, for example: does promiscuity of both the male and female species get closer or leveled, down the evolutionary track? For example, research has shown that promiscuity slows down evolution of species and thus, only those species that become less promiscuous tend to evolve and thus, survive. So, she could have cited this research and collect data based on decreasing promiscuity down the evolutionary track in a particular track of species like apes, for example, and shown that as apes evolve through intermediate stages and become human, the promiscuity would have declined and declined and finally, would have leveled. This seems to me a lot more sensible, and in a sense, more innovative than actually questioning the facts on promiscuity, because she is more prone then, as a human, to be ideologically motivated and fumble through careless distortions. For Fine’s intelligence and myth-busting skills, her arguments ought to be more concrete and established, rather than just pointing at the loopholes.

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