Men are not from Mars, Women are not from Venus

[mtvessel]

Mar 2018
Testosterone Rex - Cordelia Fine – Icon Books, 2017 (kindle edition)
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All right, I admit it. I got this book for the same reason that The Guardian is my newspaper of choice - because it confirms opinions that I already have. It has long been my view that cultural rather than biological factors are chiefly responsible for the differing roles of women and men in society, and have in the past gently criticised some who appear to think otherwise. Cordelia Fine, a psychologist and self-declared feminist, shares my skepticism, and makes a fine case for the demolition of the myth of sex-determined behavioural traits, which she calls Testosterone Rex, in this book.

A brief note on nomenclature before we continue - Fine follows what is apparently the normal definitions in her field and defines the sex of a person as referring to the gonads that they possess, and their gender as referring to the culturally constructed role that they habitually play in (or have forced on them by) society. Neither, of course, is binary, which already suggests that simplistic causal explanations linking the two are going to get messy.

The myth of Testosterone Rex starts, as so many modern myths do, with bad science. In the 1940s, the British biologist Angus Bateman did a series of experiments on mutated fruit flies. He was attempting to test a prediction of sexual selection theory - that males, being subject to greater sexual selection than females, would show a higher variation in reproductive success. Bateman used mutant flies so that individuals could be identified - this was long before the advent of genetic fingerprinting - using the patterns of mutations in the offspring and Mendelian genetics to identify the relative reproductive success of the parents. And indeed, he found what he was looking for - in one of his six studies, 21% of the males failed to reproduce against only 4% of the females. This made sense from an evolutionary perspective, because after all, making sperm is much less energy-intensive than making eggs and rearing young. Obviously males will compete to impregnate as many females as possible, and conversely females will be picky about the quality of the males they choose to mate with. So promiscuity only works as a reproductive strategy for males. Right?

Such was the success of this line of reasoning that it was held as dogma in biological circles for a number of years. But no longer. The problem is that Bateman's science doesn't stand up. One obvious issue with his methodology is that the mutations he used were so gross (microcephaly, hairlessness, hairy wings and so on) that they affected the survival of offspring, and Bateman only counted surviving young. This meant that in 4 out of the 6 studies, males apparently had more offspring overall than the equivalent number of females, which is a logical impossibility. Clearly there was a bias towards counting the offspring of males over females, so inevitably there was a greater variance in the numbers for males. Even worse, Bateman used dodgy statistics. Only his last two studies - 5 and 6 - showed the promiscuity pattern he expected to see, so he combined them and presented them as a separate graph from studies 1 to 4, which showed that females also benefited reproductively from being promiscuous (albeit less so than males). Textbooks and general discussions that presented Bateman's work generally only used the 5-6 graph and ignored the 1-4 graph.

Subsequent studies in other species have also shown that the "promiscuity benefits males and not females" hypothesis does not work in practise. Even species of birds that use leks, such as birds of paradise or sandpipers, have much more variability in male parents than the highly visible matings of successful performers would suggest (clearly a lot of rumpy-pumpy happens off-stage). Female-female competition can be a significant contributor to evolution, and so can male choosiness - the nuptial gifts accompanying mating can be a heavy investment (in the case of some spiders, it is the male's entire body as the female eats him), and there is plenty of evidence of males refusing willing females to save themselves for someone they perceive as more reproductively fit.

But surely these caveats do not apply to humans, with our enormously long gestational period (relative to body mass) of nine months, not to mention the lactational post-natal care that only mothers can give? Studies suggest that in "ideal" breeding conditions, women only produce 10-11 offspring on average in their lifetime, as achieved by Hutterite women in the early twentieth century. Whereas men's relatively minor contribution means that they could, in theory, easily father far more children than this - the psychologist David Schmidt suggests that in principle, a sexually enthusiastic man could father 100 children per year. However, Fine points out another oddity of human reproduction, which is that we are incredibly infertile. This may seem unlikely given the unsustainably large number of humans on the planet, but consider a woman having sex once per week (without contraception) for thirty years. Suppose she has nine children who survive to reproductive age. This means that for every act of intercourse that resulted in a (potentially) reproductively successful offspring, there were 173 that did not. Even excluding maternal factors, a potential lothario would have to bed over 130 women per year to have a 90% chance of just one pregnancy, let alone 100. In practice, outside harem situations the maximum number of children a man can father in their lifetime seems to be about 12-16, not so very different from women.

Still, the concept of promiscuous men and choosy women is deeply ingrained in our (western anglo-centric) culture and it is not surprising that a couple of studies did show a substantial difference in the willingness of men and women to consider a sexual encounter with a stranger. Students in a campus university were approached by moderately attractive people of the opposite sex and asked one of the following propositions: if they would a) go out with them, b) visit their apartment or c) have sex with them. A substantial proportion of the men agreed to propositions b) or c), whereas none of the women did. While on the face of it, this looks like strong evidence of higher promiscuous tendencies among young men than young women, it seems fairly obvious that this is more bad science. Among the many possible confounders, the most obvious is the female fear of risk to personal safety. Another is cultural bias - Fine does not say where these experiments were carried out, but the USA seems most likely.

Fine suggests a third reason - the sexual double standard in which there is a rich variety of demeaning epithets for promiscuous women such as sluts (a term that she says has no male equivalent), slags, or prozzies, while promiscuous men are described as gigolos, which isn't so insulting. From a linguistic point of view I have to take issue with these claims. There are plenty of terms for promiscuous men - rake, roue, cassanova, player, cad, philanderer, libertine, playboy, lothario, ladykiller, skirt-chaser, womanizer - which are not positive descriptions. They may lack the slap-in-the-face offensiveness of "slut", but there is some disapproval implied. The sexual double standard is undoubtedly real in many cultures, but it is not as great as claimed here.

But what about the structure and function of male and female brains? It is true that a large number of statistical differences have been found, ranging from grey matter volume to drendritic spike density. However, there is very little evidence that any of these structural variations result in differences in behaviour. Nor do many of the claims for sex-based differences in brain activity - such as higher use of language centres in women - pan out in meta-analyses. The model that fits the most facts is a mosaic brain, in which both men and women have a variety of brain characteristics in different admixtures. Crucially, none of these is unique to one sex or the other. You might be able to tell from a combination of a brain's physical characteristics if it is from a man or a woman, but knowing whether a brain is from a man or a woman will not help you to predict reliably the physical characteristics it will have.

The same applies to the supposed differences in male and female behaviour, such as risk-taking. Fine points out that risk is a multi-valued trait. Some people may be economically adventurous but cautious about health risks, for example - it is perfectly possible to be a hypochondriac gambler. This is in fact the common case. Risk-taking in one part of life is simply not a predictor for risk-taking in another. Which rather puts a nail in the idea that men are inherently more likely to take risks than women - there is no such thing as a risky personality. Almost everyone, no matter their sex, is mildly risk-averse - whether someone will engage in risky behaviour depends on the type of risk and the (cultural) circumstances. The same applies to willingness to engage in competitive behaviour. Most of the studies showing that men are more competitive than women turn out to have been based on tasks which are culturally gender-skewed. Ask a woman from a matrilineal society, or pick a task with a "feminine" cultural context, and women are just as competitive as men.

Getting back to biology, Fine next examines the effects of the big T - testosterone itself. This is supposed to be responsible for all sorts of characteristically masculine behaviours, but once again the story turns out to be complicated. For a start, some of its effects are mediated by turning it into a "female" hormone, estradiol, through the action of an enzyme called aromatase. Then there is the fact that it doesn't work alone - testosterone combines with cofactors to switch genes on and off and requires specialised androgen receptors to get into cells. Its effects can be counteracted by oestrogen, which does not have to be made in the gonads - the brain and several other tissues can synthesise their own. In short, there is a whole complex biochemical web which means that blood levels of testosterone alone will tell you very little about what effects it will have. Given this, one has to suspect that studies that show reduced testosterone levels in fathers who care for their children probably don't tell you much other than that child-rearing is tiring. It also explains why studies that have attempted to link financial risk-taking among traders to testosterone levels have drawn contradictory conclusions. The causes of the stock market crash in 2008 were almost certainly cultural rather than hormonal.

To me, none of this is a surprise. Evolution generally favours generalists over specialists, so hardwiring sex-determined behaviour into our brains and bodies would be a poor evolutionary choice. Retaining the ability to make appropriate adaptations to circumstance - males becoming nurturers when children need to be raised, females becoming military when homes need to be defended - seems a much better survival strategy, and fits with the mosaic brains and overlapping behavioural traits that we see. To adapt John Gray's memorable but inaccurate phrase - men are not from Mars, women are not from Venus. We are all of us from both.

Of course, statistical behavioural differences between the sexes are real. In western culture, the vast majority of domestic violence is committed by men. Most nurses are female and most software developers are male. Girls over the age of three prefer to play with pink dolls and boys with blue trains (though interestingly, the difference is much smaller if the children are presented with blue dolls and pink trains). And it is of course possible that despite the multitude of confounding factors, genetic sex does have an effect. But far more likely is that gender stereotyping imposed by cultural environment is to blame. Humans are unusual in the degree to which we ape each other - far more so than other great apes. Fine cites developmental psychologists who claim that children are "gender detectives" who learn their roles by copying the people they see who are like them. If you want your child to play with gender-neutral or counter-stereotypical toys, show them a child of the same sex who is already playing with them.

The nature-nurture war will undoubtedly continue, but Fine does a good job of tipping the scales in favour of the latter - I should add that she has a witty and enjoyable style too, using jokey observations of her home life and sarcastic asides to buttress her arguments. And her conclusion that cultural rather the genetic factors are at play is to me a hopeful sign that a better, more equal balance between the sexes could be achieved quite quickly. The power of cultural conditioning should not be underestimated, but there are plenty of examples of rapid change in social behaviours. Whereas if gendered behaviour is hardwired, there is not a lot that we can do, short of eugenics. Fortunately, that is not what the science says. The good science, anyway.