Testosterone Rex

Unmaking the Myths of Our Gendered Minds

Cordelia Fine

• Publisher: Icon Books
• Year: 2017
• ISBN:
  9781785781629
• Topic: Biological Sciences
• Subtopic: Neuroscience
• Index: Biological Sciences

WINNER OF THE 2017 ROYAL SOCIETY INSIGHT INVESTMENT SCIENCE BOOK PRIZE What the judges said: 'Every man and woman should read this book on gender bias... an important, yet wickedly witty, book.' 'Fine's entertaining and thoughtful book is a valuable addition to the discussion about gender.' Ian Critchley, Sunday Times 'In addition to being hopeful, Fine is also angry. We should all be angry. Testosterone Rex is a debunking rumble that ought to inspire a roar.' Guardian 'A densely packed, spirited book, with an unusual combination of academic rigour and readability... The expression "essential reading for everyone" is usually untrue as well as a cliché, but if there were a book deserving of that description this might just be it.' Antonia Macaro, Financial Times Testosterone Rex is the powerful myth that squashes hopes of sex equality by telling us that men and women have evolved different natures. Fixed in an ancestral past that rewarded competitive men and caring women, these differences are supposedly re-created in each generation by sex hormones and male and female brains.Testosterone, so we're told, is the very essence of masculinity, and biological sex is a fundamental force in our development. Not so, says psychologist Cordelia Fine, who shows, with wit and panache, that sex doesn't create male and female natures. Instead, sex, hormones, culture and evolution work together in ways that make past and present gender dynamics only a serving suggestion for the future – not a recipe. Testosterone Rex brings together evolutionary science, psychology, neuroscience and social history to move beyond old 'nature versus nurture' debates, and to explain why it's time to unmake the tyrannical myth of Testosterone Rex.For fans of Fine – whose Delusions of Gender 'could have far-reaching consequences as significant as The Female Eunuch ' (Viv Groskop, Guardian ) – and thousands of new readers, this is an upbeat, timely and important contribution to the debate about gender in society.

PART ONE

PAST

CHAPTER 1

FLIES OF FANCY

BACK IN THE MISTS OF TIME THAT THANKFULLY CAST A HAZE over my dating career, I became entangled with a man who drove a Maserati. When I let this slip to my mother, she responded in the unnaturally bright tone of voice she uses whenever, in deference to my technical state of adulthood, she wishes to disguise the fact that she thinks I have made a decision that will lead inexorably to disaster. “Fancy, a Maserati!” she exclaimed. “Does he have many girlfriends?”

The unsubtly implied connection has an interesting scientific history.¹ In the middle of the last century, the British biologist Angus Bateman carried out a series of experiments with fruit flies. They would eventually become the wellspring of a flood of claims about the psychological differences that have evolved between women and men. If you have ever come across the idea that men drive Maseratis for the same reason that peacocks grow elaborately ornamental tails, then you have been touched by the ripples of this landmark study. Bateman’s research was inspired by Darwin’s theory of sexual selection, which was a much debated subtheory within Darwin’s widely accepted theory of natural selection. (Natural selection is the process whereby the frequency of different versions of a heritable trait change over time, due to some varieties of a trait leading to greater reproductive success than others.) Sexual selection theory was, in part, an attempt to make sense of the mystery of why the males of many species display extravagantly showy characteristics, like the peacock tail. These phenomena demanded an explanation because they were so awkward for Darwin’s theory of natural selection. After all, if a primary goal of your life is to avoid being eaten by another animal, then a large, eye-catching, wind-dragging, feathered rear sail is not an asset.

Darwin’s explanation drew on richly detailed observations of animals and their mating habits. (As one Nature journalist observed of that period of history, “despite the Victorians’ reputation for prudishness… there were few places in the world where courting animals could escape the note-taking naturalist.”)² These field studies gave rise to Darwin’s famous observation in The Descent of Man, and Selection in Relation to Sex that the cause of males’ deviation from the female form

seems to lie in the males of almost all animals having stronger passions than the females. Hence it is the males that fight together and sedulously display their charms before the female.³

On the fighting side, more formally known as intrasexual competition, Darwin proposed that some characteristics (like an imposingly grand size or an intimidatingly large pair of antlers) are usually selected for more strongly in males. This is because these kinds of features increase a male’s reproductive advantage by enhancing his ability to fight against other males for access to females. On the other hand, more whimsical characteristics—like a splendid plumage, a tasteful odour, or an intricate song—have their positive effect on reproductive success by boosting the male’s appeal as a mate for the female. This dynamic is termed intersexual competition.

Darwin acknowledged that the pattern he’d described was sometimes reversed, with females being competitive or ornamented, and males appearing in the choosy, less spectacular style. But this was less common because, Darwin suggested, the challenge to be chosen usually fell more strongly on males than on females. He implied that this was due somehow to differences in the size and mobility of sperm versus eggs. But it was Bateman who, picking up on this idea and developing it, offered the first compelling explanation for why it is that males compete, and females then choose from among them.

The goal of his research was to test a prediction from sexual selection theory. Just like natural selection, sexual selection needs variation in reproductive success in order to work: if everyone is equally successful in producing offspring, there’s no basis on which to weed out less successful individuals. If, as Darwin suggested, sexual selection acts more strongly on males, then this implies greater variation in the reproductive success of males than in females—that is, a wider range between the least, and the most, reproductively successful individuals. Bateman put this assumption to the test for the very first time.⁴

To do this, he ran six series of experiments in which male and female fruit flies (Drosophila melanogaster) were trapped together in glass containers for three to four days. At the end of this period, Bateman worked out as best he could how many offspring each male and female had produced, and from how many different mates. He needed considerable ingenuity to do this, since the discipline of molecular biology, that today brings paternity-testing kits to supermarket shelves, did not exist in the 1940s.

A screen-buff might be tempted to describe the solution he came up with as a cross between Frankenstein and Big Brother. Each fly in his series was inbred with a different, distinctive mutation: some with charmingly evocative names (like “Bristle,” “Hairless,” and “Hairy-wing”); others distinctly creepier (such as the miniature- or even no-eyed “microcephalous” fly). Each fly had one dominant mutant allele (one of the two copies of a gene) and a recessive normal one: meaning, as you might distantly recall from high school biology class, roughly a quarter of the offspring would end up with a mutation from both mother and father, a quarter from the father alone, and another quarter from the mother alone. (The last lucky 25 per cent of the offspring would have no mutations at all.) This principle of genetic inheritance enabled Bateman to estimate how many offspring each male and female had produced, and how many different mates a fly had enjoyed.

The outcome of Bateman’s six series of matchmaking was the first scientific report of greater male variation in reproductive success. For example, 21 per cent of males failed to produce any off-spring, compared with only 4 per cent of females. Males also showed greater variation in the estimated number of mates. But it was the linking of the two findings that became the basis of explanations for why males compete and females choose: Bateman concluded that although male reproductive success increased with promiscuity, female reproductive success did not. His critically important explanation was the now familiar insight that male success in producing offspring is largely limited by the number of females he can inseminate, whereas a female gains nothing from further pairings beyond a single one (since her first mate should furnish her with plenty more sperm than she needs).

Interestingly, Bateman’s study was largely ignored for over twenty years.⁵ Then his argument was expanded in a landmark paper by the evolutionary biologist Robert Trivers.⁶ In this paper, the economics of egg and sperm production was made more explicit, being expressed in terms of the larger female investment of a big, costly egg compared with the male’s minuscule contribution of a tiny, single sperm. Trivers also pointed out that the lopsided costs of reproduction can go well beyond sex differences in the size of the original contribution of gametes (that is, the egg versus the sperm) to include gestation, lactation, feeding, and protection. Any female readers who have themselves reproduced will, I’m sure, be inclined to agree with this point about the substantiveness of the female mammalian reproductive role. (My own personal understanding of this deep truth occurred during my first pregnancy, on reading an unhelpfully vivid description of childbirth as a physical feat comparable to a person making their way out of a car via the exhaust pipe.) The more highly investing sex—usually females—should therefore hold out for the best possible male, Trivers speculated, as the costs of a poor-quality mating are considerable. But males would do best to compete with other males in order to spread their cheap, mass-produced seed among as many females as possible. A follow-up implication, argued Trivers, is that males usually have less to lose and more to gain from abandoning existing offspring in pursuit of a new mate.

The Bateman paradigm, as it’s sometimes known, was for a long time “the guiding principle and cornerstone for much of sexual selection theory.” As University of Missouri–St. Louis evolutionary biologist Zuleyma Tang-Martínez puts it:

Up until very recently, the unquestioned assumptions underlying the study of sexual selection have been that eggs are expensive while sperm are unlimited and cheap, that males should therefore be promiscuous while females should be very choosy and should mate with only the one best male, and that there should be greater reproductive variance among males (as compared to females) because it is males that compete for females and mate with more than one female. Since females are, presumably, mating with only one male, this means that some males may mate with many females, while others may mate with few or none. This reproductive variance is then responsible for the sexual selection of traits possessed by the more successful males.⁷

Indisputably elegant, Bateman’s conclusions, elaborated by Trivers, enjoyed the status of universal principles for many years. They also became the bedrock of claims about evolved differences between women and men, in which peacock tails are replaced with Maseratis, corner offices, or big shiny trophies. Just replace the phrase “many females” with “many girlfriends” and “traits possessed by the more successful males” with “Maseratis possessed by the more successful males” and the dots are all connected. From this evolutionary perspective, a woman aspiring to high status is a bit like a fish aspiring to a bicycle.

But in the past few decades there has been so much conceptual and empirical upheaval over sexual selection in evolutionary biology that, according to one professor in that field I spoke to, the classic Bateman and Trivers papers are now largely cited for sentimental reasons. And startlingly, the first set of contradictory data we’ll look at comes from Bateman’s own study.

ALTHOUGH BATEMAN’S CONCLUSIONS tend to evoke images of the Playboy Mansion or well-stocked harems, it’s necessary for the time being to return to Bateman’s unsalubrious glass containers. It was only in our young century that, noticing that this (ahem) seminal paper had never been replicated, or apparently even subjected to close inspection, the contemporary evolutionary biologists Brian Snyder and Patricia Gowaty reexamined it. As they acknowledge, they returned to the study with many advantages that Bateman had lacked. These included modern computational aids, more sophisticated statistical methods and—perhaps I can dare to add?—fifty years of feminist insights into how cultural beliefs can affect the scientific process.⁸ Like other modern critics of the Bateman study, Snyder and Gowaty expressed considerable admiration and respect for Bateman’s “groundbreaking” study. But as they point out, given its “foundational nature,” it was “important to know that Bateman’s data are robust, his analyses are correct and his conclusions are justified.”⁹ As it happens, no such reassurance was forthcoming. Snyder and Gowaty’s inspection revealed some significant problems.

For a start, as you’ll recall Bateman used different mutant Drosophila strains so that he could infer reproductive success from the particular pattern of abnormalities passed on to each offspring. If this method had you squeamishly pondering the grisliness-squared of a fly unfortunate enough to inherit both a maternal and a paternal mutation, you are one step away from a significant problem: these mutations turned out to affect offspring viability, and Bateman only counted surviving young in his tallies.¹⁰ But if, on the other hand, a fly was more likely to survive because it had only one mutation, or none, then it could only be assigned, at best, to one parent. With the parentage of so many fertilizations completely or partially unaccounted for, this left considerable scope for error. While Bateman recognized this issue, Snyder and Gowaty quantified it. They noticed that in two-thirds of Bateman’s series of experiments, his data indicated that males had produced more offspring than the females: a logical impossibility, since every offspring of course had both a father and a mother. In other words, the data had been biased towards counting the offspring of males.¹¹ This bias is important because the very point of the study was to compare male and female variance in reproductive success, yet the data were biased in ways likely to inflate estimates of the male variance.

Even setting aside this source of bias in Bateman’s data, a vital problem remains, raised first by Tang-Martínez and Brandt Ryder.¹² While recognizing that Bateman’s study was “ingenious and elegant,”¹³ they also pointed out that his famous finding that only males benefit from promiscuity—immortalized into a universal principle—actually only applied to his last two series of experiments. For reasons that remain obscure,¹⁴ Bateman analysed the data from the first four series separately from the last two, and presented them in two separate graphs. Remarkably, females did show greater reproductive success with a greater number of mates in the first four series, albeit less so than males. But in the discussion section of his article Bateman focused primarily on the results that fit the notion of competitive males and choosy females. As Tang-M...