University of Rochester

On the Origins of Diversity

Sometimes the ‘exceptions’ prove the rules need to change, says a noted biologist. By Scott Hauser

Given the way Joan Roughgarden ’68 describes herself and some of her colleagues, you’d think she’d spent the past several years studying the evolution of biologists.

A scholar whom The New York Times recently described as “at the top of [her] game” as a theoretical ecologist, Roughgarden has spent much of her 30-year career as a field researcher and scholar at highly regarded universities, the academic habitat that’s home to biological scientists.

For the past year, the professor of biological sciences and geophysics at Stanford University has been closely observing what happens when biologists are presented with a 480-page, newly published challenge to Darwin’s theory of sexual selection, one of the pillars of modern evolutionary theory.

It’s a little like an astronomer telling Ptolemy about a guy named Copernicus. . . .

“Most biologists are unprepared for the critical inspection of the theories that their work is a part of,” says Roughgarden, who 36 years ago graduated from Rochester as Jonathan Roughgarden. “They’re very good at adducing facts, but they’re not very good at making sense of the facts or at understanding them in a larger narrative.

“The argument usually is not about the facts. The argument is about the story.”

“[Evolutionary biologists] need to stop being so defensive about Darwin’s theory, roll up their sleeves, and start coming up with a theory that explains what we actually see.” —Joan Roughgarden ’68, professor of biological sciences at Stanford University

Roughgarden, who honed many of her critical reasoning skills as a biology and philosophy double major at Rochester, is bringing the argument about the story of evolution into the not-always-so-polite academic parlor with her new book, Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. Published last May by the University of California Press, the book blends biological science, politics, public policy, religion, and social ethics to argue for a more tolerant understanding of human diversity.

She devotes the majority of the book—about 200 pages—to cataloging examples from roughly 300 different vertebrate species that are known to change genders over the course of their lives, that straddle the boundary between genders, or that engage in same-sex relationships. Along the way, she posits her own theory, which she calls the “theory of social selection,” that emphasizes the role of cooperation rather than competition as the driving force for ensuring that an animal’s genes get into the next generation.

Drawing from those scientific examples, along with examples from the Bible, anthropology, sociology, popular culture, and from her experience as a transgendered woman, Roughgarden makes the case that a rigid view of sex and gender tracing its ancestry to Darwin has hindered modern interpretations of diversity.

“Sexual selection theory has long been used to perpetuate ethically dubious gender stereotypes that demean women and anyone else who doesn’t identify as a gender-normative heterosexual male,” Roughgarden writes.

While both academic and nonacademic reviewers have applauded Roughgarden’s effort to broaden the scope of discussion surrounding diversity, many say it’s too early to toss the Darwinian baby out with the bathwater.

In the July 30 issue of the British weekly The Times Literary Supplement, evolutionary biologist Jerry Coyne of the University of Chicago argues that Roughgarden is selective in the examples she uses.

“She ignores the much larger number of species that do conform to sexual selection theory, focusing entirely on exceptions,” Coyne writes. “It is as if she denies the generalization that Americans are profligate in their use of petrol by describing my few diehard countrymen who bicycle to work.”

But Robert Dorit, associate professor of biological sciences at Smith College, calls the book “thought provoking” and “profound.” Writing in the September-October 2004 issue of American Scientist, he says, “[R]egardless of the eventual success of the formulation, Evolution’s Rainbow will change the way many biologists view the world, making it easier for them to see additional instances of diversity in genders, sexual phenotypes, and sex roles. That’s real progress.”

Roughgarden posits what she calls the “theory of social selection,” which emphasizes cooperation rather than competition as a driving force behind evolution.

It was a progressively deeper understanding of how species evolve that led Darwin to propose in the late 19th century what’s become known as the theory of sexual selection. The basic idea is that the males of a species try to outdo each other in a competition to attract the attention of—and mate with—as many females as possible, sometimes going so far as to develop traits like showy plumage and oversized antlers that may be counterproductive to an individual’s overall chances of survival.

According to sexual selection theory, males are evolutionarily programmed to share freely the genetic material that they carry in abundance in their sperm. Females, on the other hand, are geared to be careful consumers in choosing the right mate to have access to their less abundant eggs.

To biologists, the distinction between sperm and egg is crucial because it lies at the heart of the differences between the sexes. Biologically, the definition of “male” is a member of a species with small gametes, or the cells that carry one-half of an individual’s chromosomes. A “female” is a member of a species with large gametes. The combination of gametes during sex results not only in a possible new member of the species but also in an important intermingling of genetic information.

The definition of gender, on the other hand, has little to do with gamete size but involves differences in body appearance, behavior, and other traits, Roughgarden points out.

She argues that the sexual selection theory often conflates sex and gender into a simple template of “the ardent male and the coy female,” an archetype that doesn’t always fit the evidence found in the natural world.

How, for example, does the theory account for a species of hyenas in which the females all have external, male-like sex organs? Or a species of coral reef fish that has two versions of males but one version of females? Or another species of fish that’s hermaphroditic?

Since the 1970s, evidence of the existence of such diversity has grown, Roughgarden says, although few biologists have studied it in depth.

“It’s one of those things where most scientists have been proceeding merrily along,” she says.

While biologists have recognized that many species don’t fit well into Darwin’s theory, most standard theorists argue that the examples are either not yet well understood or are anomalies among the tens of thousands of vertebrate species.

Instead, Roughgarden argues that animals have evolved an elaborate basket of tactics to build up and to trade on social coalitions to ensure their survival. Sometimes those coalitions are based on relationships between sexes, just as the sexual selection theory describes, but many times those relationships involve dynamic and fluid combinations of sex and gender.

“I don’t privilege any particular narrative,” she says. “Every animal has the same definition of fitness—namely the number of young placed in the next generation—but they have different tactics to achieve that goal.”

She bases her ideas on a version of game theory that emphasizes cooperation and bargaining tactics, a model developed by John Nash, the Nobel Prize-winning mathematician whose life was featured in the movie A Beautiful Mind and who’s better known for his ideas about competitive game theory.

Roughgarden’s interest in mathematical modeling and biology continues an aspect of her career that began at Rochester. Having grown up in the Philippines and in Indonesia, where her father, a construction engineer, was a quasi missionary for the Episcopal church, Roughgarden and her family were back in the United States when it was time for her to go to college.

At Rochester, she worked with the late biology professor Wolf Vishniac, but she also added a major in philosophy, part of a rigorous courseload that she now credits with helping her analyze subjects critically.

“My writing improved enormously as a result,” she says.

From Rochester, she went on to Harvard for a Ph.D. and taught at the University of Massachusetts before joining the faculty at Stanford in 1972.

Roughgarden ’68 argues that the Darwinian view of sex and gender has hindered interpretations of diversity.

Roughgarden admits that she hadn’t given much thought to gender diversity in the animal world until about 1997, when she was about to undergo the procedures to become a woman. As she joined the 500,000 people who turned out for the Gay Pride March in San Francisco, she had something of an epiphany.

“This was a red flag to me, because a theory that says there’s something wrong with so many people may itself be wrong,” Roughgarden says.

And as she found more examples that ran counter to Darwin’s theories, the more intrigued she became.

“A lot of scientists wanted me to stop there and just stand back and look at it, and say, ‘My gosh, we have a lot of work to do,’” she says. “Maybe they can admit that they need to widen Darwin, but I’m not going to put any work into trying to resuscitate the theory of sexual selection.

“They need to stop being so defensive about Darwin’s theory, roll up their sleeves, and start coming up with a theory that explains what we actually see.”

That explanation is important, she says, because like many theories in science, the scientific interpretation has implications beyond textbooks.

For the past century, many who have discriminated against gay, bisexual, and transgendered people have couched their arguments in Darwinian terms of what’s “natural.”

She had not planned to challenge Darwin when she set out to write the book, but she hopes her work sparks conversations about the misguided use of biology to justify social limitations.

“It’s not whether Darwin was right or wrong, but that the key archetype is wrong, and it’s important to say that it’s wrong because it’s the source of a lot of social injustice,” Roughgarden says. “The fact that it has bad social implications means that we have to be really sure that it’s scientifically correct. And if it isn’t, then we should junk it pretty fast.”

Scott Hauser is editor of Rochester Review.