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Unpicking the myth of Testosterone Rex

Our long-held views on what causes gender differences are wrong. A new book argues it’s more complicated than we think.

Imagine this thing called Testosterone Rex. According to the old tales, he – most definitely he – is a dangerous beast: powerful; aggressive; competitive; risk-taking; promiscuous and potent, able to sire a hundred babies every year, from as many partners.

Or consider, perhaps, Testosterone Rex as a force. Measured in mere nanograms, this potent hormonal essence surges in gestation to physically determine if we become male rather than female. But more than that, says the old wisdom, it is “that special substance” that gives men and women intrinsically different natures, making them two separate kinds of people.

Better yet, see it as a mindset, grounded in tradition. Testosterone Rex, says Cordelia Fine, is “that familiar, plausible, pervasive, and powerful story of sex and society. Weaving together interlinked claims about evolution, brains, hormones, and behaviour, it offers a neat and compelling account of our societies’ persistent and seemingly intractable sex inequalities”.

Professor Cordelia Fine is using scientific evidence to challenge popular beliefs. Picture: Paul Burston

But, says Fine, Professor in History and Philosophy of Science at the University of Melbourne, advances in scientific understanding have made this T Rex extinct.

And even if it is not quite expired, Professor Fine, through her new book Testosterone Rex: Unmaking the Myths of Our Gendered Minds, has fired a burst of well-aimed silver bullets into its quivering carcass.

The book is a sharp corrective to the pop science of men from Mars and women from Venus. Professor Fine has been described as “the mistress of ‘it’s a bit more complicated than that’” and she assembles a mass of scientific evidence – across biology, anthropology, psychology and neuroscience – to disprove the myth that testosterone, or the lack of it, shapes men and women into virtually separate species.

We are spellbound by biological sex, she writes. “After all, sex categories – whether you have female or male genitals – are obviously fundamental for reproduction. Sex categories are also the primary way we divide the social world.”

Professor Fine’s new book

When a baby is born their sex is usually the first thing asked about them and it may be the last thing we remember of them – after a lifetime of their being directed down a “male” or “female” stream in school, play, work and social status.

“Perhaps it’s not surprising, then, that we often think of biological sex as a fundamental force in development that creates not just two kinds of reproductive system, but two kinds of people.”

At the core of this view is “a familiar evolutionary story” that University of Exeter philosopher of science John Dupre calls “The Biological Big Picture”, Professor Fine tells Pursuit. “It’s the big picture of sex difference which starts with the fact that sperm are cheap and eggs are expensive. It argues that as a result of this discrepancy in reproductive investment we’ve evolved different natures.

“Men have evolved to be more promiscuous, risk-taking, and status-seeking than women, and because these differences reflect evolved adaptations, they are timeless and universal, implemented through the stable mechanisms of biological sex.

“The T Rex view constrains our image of what gender equality can look like. Of course, the Rex version can include equal opportunities, regardless of sex. But if on average we have different sets of dispositions, then we will always see sex segregation in the kind of jobs people do and the places they reach in hierarchies. We could want that kind of equality, and we could strive for it, but biology is standing in our way.”

chasing down the science

Testosterone Rex is Professor Fine’s second book on this theme. Delusions of Gender: The Real Science Behind Sex Differences, calls out the unintentionally biased assumptions often at work in investigations of the neural basis of human sex differences, as well as the blatant misrepresentations and misunderstandings of the science in popular media. She coined the term ‘neurosexism’ to describe the misuse of neuroscientific claims or language to reinforce gender stereotypes in ways that are not scientifically justified.

Her interest in this area was in part triggered by her personal life. With two young children, she was reading a lot of parenting books. A number of these claimed that neuro-imaging technology showed profound differences between male and female brains – with implications for parenting, teaching and the workplace.

Some parenting books claim there are profound differences between the male and female brain. Picture: Shutterstock

Unlike most readers, Professor Fine chased down the science behind the claims: “I was really shocked at the disconnection between what the scientific evidence showed and what the popular writers were saying … that men and women have profoundly different brains and think in profoundly different ways, and it’s hard-wired. But of course the science wasn’t saying anything close to that.”

Victorian-era scientists measured skull volumes by filling them with lead shot and so deduced that women were less intelligent because their skulls were smaller. “They were trying to locate the basis of social structure and sexual inequality in the brain,” she says.

She recognises the importance of research into sex influences on the brain in contemporary research, but found that continuing implicit assumptions that men and women are essentially different subtly influenced how the research was designed, how the data were analysed and the interpretations that were made.

The myth of Testosterone Rex is permeated with similar deep-seated beliefs.

Myth presented as fact

Fine even quotes a Formula 1 magazine which argues: “A 21st century human has a stone age brain … the rewards of survival and of course mating resulted in a male brain tuned for hunting, aggressiveness and risk-taking … Females were of course during the same period honed to raise and defend offspring. This of course all sounds deeply sexist but it is a combination of historical fact and recent scientific study.”

Testosterone is often thought to be the hormonal essence of masculinity that drives these evolved differences, and its influence is rarely underestimated. Think how often we groan, “It’s the testosterone.” In a recent book, University of Cambridge neuroscientist Joe Herbert is emphatic: “At the end of any discussion of the impact of testosterone on the history of mankind in all its wide-reaching and powerful complexity, a simple fact remains: without testosterone there would be no humans to have a history.”

Professor Fine retorts: “Now there’s a conclusion to inspire the reverence the testicle deserves … or at least until you realise that the same fact applies to estrogen, carbon, and even that dullest of elements, nitrogen. But still – Sex! Power! The will to win!”

But she builds a case, across species and fields of study, to buttress her argument that the role of biological sex in development is more complicated than we think, and that testosterone is not king. Even in non-human animals, for instance, evolution has allowed for the roles males and females play in reproduction to respond to the context. The Two-Spotted Goby, for instance: at the beginning of its mating season the males are fiercely competitive, while at the end, when males are in short supply and exhausted, the females turn sexually assertive.

This points to a factor that’s often overlooked when we think about male and female adaptive behaviour: the role of the environment.

“We tend to think ‘adapted’ equals ‘in the genes’,” says Professor Fine, “particularly when we are thinking about masculine or feminine behaviour. But animals don’t just inherit genes, they inherit an entire ‘developmental system’ – a nest, a mother, playmates and, in the case of ourselves, a rich culture. Evolutionary processes can and do recruit these stable resources for the development of adaptive behaviour. And this means that if relevant environmental conditions change, so too does the trait.”

A striking example of this is sexual imprinting. “Having sex with the right species is pretty fundamental when it comes to reproductive success,” she points out. “And yet male sheep and goats cross-fostered by a mother of the other species develop a cross-species sexual preference.”

Genetics only tell us part of the story about how a human will behave. Picture: Shutterstock

At the same time, there are two important shifts taking place in the science of sex. One is a move away from the idea that biological sex creates discrete male and female brain circuits that underlie mating behaviour – which, as Professor Fine points out, to some commentators “potentially includes in its scope just about every aspect of human psychology – from a visual system attuned to babies’ faces, to a sense of humour that showcases one’s superior reproductive potential.”

Instead, sex interacts in complex ways with many other factors throughout the brain to create dynamic and idiosyncratic ‘mosaics’ of features.

There’s also growing interest in indirect ways that sex can influence the brain – for instance, via effects on the body and the responses this evokes in others.

A complicated reality

So where does testosterone fit in?

“Although there is a popular perception that ‘more T’ means ‘more masculinity’, the reality is much more complicated,” says Professor Fine. Her book shows just how far current scientific evidence takes us from “the simple T-Rex view, in which testosterone fuels male competition in direct proportion to the stable quantity of it roiling in the bloodstream”. Testosterone is neither necessary nor sufficient for competition, can take second-place to context and experience, and is sometimes a mere middle-man for the influence of our gender constructions.

“And this makes sense, given what we know about women and men,” says Professor Fine. As she explains in her book, the dynamic ‘mosaicism’ we see in our brains is also a feature of our patterns of ‘masculine’ and ‘feminine’ behavioural traits. We might even be financially risk-taking but physically risk-averse. “So what particular attributes of masculinity should we expect a high-T man to show or a low-T woman to lack?”

Moreover, she tells Pursuit, Testosterone Rex can stand in the way of clear and optimistic thinking about sex inequality.

“The T Rex story tells us that masculinity is a male adaptation, and therefore that ‘boys will be boys’. But the contemporary science is telling us a very different story.”

Testosterone Rex: Unmaking the myths of our gendered minds is published by Icon Books. In stores now. RRP: $29.99

Banner Image: Unsplash

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