Cordelia Fine - Testosterone Rex: Myths of Sex, Science, and Society

For Isaac and Olly

Copyright 2017 by Cordelia Fine

All rights reserved
First Edition

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The Library of Congress has cataloged the printed edition as follows:

Names: Fine, Cordelia, author.
Title: Testosterone rex : myths of sex, science, and society / Cordelia Fine.
Description: First edition. | New York, N.Y. : W.W. Norton & Company,
[2017] | Includes bibliographical references and index.
Identifiers: LCCN 2016031608 | ISBN 9780393082081 (hardcover)
Subjects: LCSH: Sex (Psychology) | Sex (Biology) | Sex.
Classification: LCC BF692 .F525 2017 | DDC 155.3dc23 LC record available
at https://lccn.loc.gov/2016031608

ISBN 978-0-393-25388-7 (e-book)

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But in addition to being angry, I am also hopeful,
because I believe deeply in the ability of human beings
to make and remake themselves for the better.

CHIMAMANDA NGOZI ADICHIE,

We Should All Be Feminists

ALSO BY CORDELIA FINE

Delusions of Gender: How Our Minds, Society,
and Neurosexism Create Difference

A Mind of Its Own:
How Your Brain Distorts and Deceives

B ACK 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.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 Darwins 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.

Darwins 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.) These field studies gave rise to Darwins 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.

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 males reproductive advantage by enhancing his ability to fight against other males for access to females. On the other hand, more whimsical characteristicslike a splendid plumage, a tasteful odor, or an intricate songhave their positive effect on reproductive success by boosting the males appeal as a mate for the female. This dynamic is termed intersexual competition.

Darwin acknowledged that the pattern hed 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, theres 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 femalesthat 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.

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 percent 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 Batemans six series of matchmaking was the first scientific report of greater male variation in reproductive success. For example, 21 percent of males failed to produce any offspring, compared with only 4 percent 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).