W.W. NORTON, JANUARY 2017There is a myth that male and female natures are distinct, shaped by ancient evolutionary pressures and transmitted faithfully and timelessly via sex chromosomes and hormones, against which equal opportunity laws and optimistic feminists are no match. This myth is so familiar that every reader can fill in the chain of argument required to get from “cheap sperm” to an explanation of why there are many more male than female Nobel Prize winners. What’s more, the issues I dissect in my latest book, Testosterone Rex: Myths of Sex, Science, and Society, are part of every scientist’s life. Of course only a subset of scientific research examines the often-contentious zone of how systems of sex, gender, or both impact the brain and behavior. But just about every researcher is, at some point, part of conversations and disagreements as to why men predominate in a...

The debates are ubiquitous, whether they concern gender gaps in science, senior leadership roles, or entrepreneurship. The “nature” side claims a small triumph or two: some hormonal effect, anatomical brain difference, or evolutionary principle that seems to prove the naturalness of a particular gender gap. But then the “nurture” side enjoys a few gains—a demonstration of workplace gender bias, an unfavorable comparison with a more egalitarian country, or a study showing that in some situations the sexes aren’t so different after all—that seem to finger stereotypes and sexism as culprits. And, of course, each side regularly challenges claims made by the other, dismissing the reliability, validity, or applicability of this or that finding.

Testosterone Rex seeks to transform the debate by taking a closer look at phenomena we usually think of as falling into the “nature” basket: the development of sex-specific adaptive behaviors, the role of sex in brain development, and the effects of higher testosterone levels. For example, evolutionary biologists have documented evidence, both across and within species, showing that biological sex doesn’t have straightforward consequences for courtship patterns or mating behaviors. Sperm provisioning isn’t as biologically cheap as was traditionally assumed, nor are competition and social dominance as irrelevant to females’ reproductive success.

In neuroscience, the traditional model in which sex has a powerful, monolithic effect on the brain is being replaced by one in which the genetic and hormonal components of sex are among many factors that interact in complex ways. There is also growing appreciation that sex can also act indirectly on the brain and behavior through tangible effects on size, strength, smell, appearance, and so on. In other words, gender socialization isn’t something that tinkers around the edges of the real developmental work of sex, but is an integral part of it. And in behavioral endocrinology, scientists are building on animal research that shows the importance of steroid hormones such as testosterone for behavioral plasticity to help unravel the biological links between gender constructions and hormonal state.

The Testosterone Rex myth persists in popular understanding of the gender dynamics of society. It also lurks in outdated models and assumptions in some areas of research, pinning the gender gap in retirement savings or even the global financial crisis on men’s higher testosterone levels. But science has evolved, and the Testosterone Rex myth is as extinct as the T. rex. It’s time to say good-bye, and move on. 

Cordelia Fine is a professor in the History and Philosophy of Science Programme in the School of Historical and Philosophical Studies at the University of Melbourne in Australia. Read an excerpt of Testosterone Rex.

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