“The facts speak for themselves, and the facts are that biologists have been covering up the extent of certain sexuality, homosexuality, and all kinds of gender and sexuality expressions.”
From philandering men to gold-digging women, Darwin’s theory of sexual selection has been used to provide rationale for a variety of social and sexual behaviors. Originally proposed to account for physical divergences between males and females of the same species (e.g., the appearance of the peacock vs. that of the peahen), sexual selection postulates that, in general, males develop aggressive, showy traits to compete for the attention of passive, choosy females. In today’s post-feminist world, researchers have extended the theory from simple male vs. male competition to include female competition and intersexual competition, as well. Joan Roughgarden thinks Darwin just plain got it wrong.
A biologist at Stanford University, Roughgarden believes it’s time to discard sexual selection’s theoretical framework. In a 2006 review in the journal Science, she argued that sexual selection is “always mistaken,” even in species like the peafowl, whose “gender roles seem to match the Darwinian templates.” Today, she contends that “for any given species, if you look hard enough, sexual selection fails.” It is a hard-line position that has made her one of evolutionary biology’s most controversial figures.
With a career spanning nearly 40 years, Roughgarden is no young upstart. In 1971, after just three years of graduate work, she received her doctorate from Harvard University and joined the faculty of Stanford University. Conscious of her brief graduate career, she was determined to continue her education as an assistant professor and sat in on courses in a number of different departments. Bringing this interdisciplinary approach to her own research, she both created mathematical models to explain how ecosystems function and tested those models in field experiments.
But outside the lab, Roughgarden crossed a much deeper divide. Born a male, it wasn’t until 1998, at the age of 52, that Jonathan Roughgarden took a sabbatical to complete his physical transformation into Joan. The procedure carried some professional risk: According to The National Center for Transgender Equality, only 31 percent of Americans live in areas that explicitly ban discrimination based on gender identity and expression. It is common for transgendered people to lose their jobs. In Roughgarden’s case, she credits her ability to stay at Stanford to then-provost Condoleezza Rice, whom she describes as someone “quite sensitive to diversity.”
Perhaps the most surprising part of Roughgarden’s transformation was the effect it had on her scientific interests. The epiphany came at her first lesbian, gay, bisexual, transgender Pride Parade in San Francisco. Prior to this experience, she says she had no reason to doubt the general scientific consensus that homosexuality in nature was a simple irregularity—an academic dead end. But as she marched with thousands of people in the parade, she couldn’t help but question the status quo. “When I saw all these people, I knew that there was a big problem. It was just obvious…when something like 10 percent of the population has a phenotype, then that’s prima facie too common to be interpreted as a disability or a disease or something. And that is the party line in biology.”
In Roughgarden’s view, biologists have categorized homosexuality and other non-reproductive sexual behaviors as “aberrations” or rare exceptions to the rule. She decided to study the diversity of animal sexual behaviors. She eventually compiled the material into a book titled Evolution’s Rainbow. Published in 2004 and written for the non-scientist, it catalogues hundreds of species with a plethora of scandalous behaviors, from ejaculatory anal sex in male bighorn sheep, to orgasmic genital rubbing in female bonobo chimps, to a sort of ménage-à-trois in the bluegill sunfish. According to Roughgarden, these behaviors, one after another, present the field of evolutionary biology with a challenge the sexual selection framework does not meet.
In his 1871 treatise on sexual selection, Darwin wrote, “Males of almost all animals have stronger passions than females,” and “the female…with the rarest of exceptions is less eager than the male.” In the 20th century, biologists like Robert Trivers supported Darwin’s generalized narrative of passionate males and passive females using what is now called parental investment theory. In this model, females choose their partners carefully because of the time and effort of egg production, pregnancy, and/or childcare. Males, on the other hand, invest little energy in sperm production or rearing offspring, so their most effective strategy is to mate widely and often. In this way, the differential parental investment of the two sexes gives rise to the traditional “battle of the sexes,” which continues to surface in popular culture today—males chase quantity, while females choose quality.
But in the 1970s and 1980s, the women’s movement questioned traditional sex roles and brought more women into the lab. Soon, sexual selection’s Victorian view was revised. Through the work of Sarah Hrdy, Patricia Gowaty, and many others, new data accumulated to challenge the stereotype of the “passive female.” Although most evolutionary biologists agree that the parental investment theory provided a useful framework that stimulated the acquiring of new data, many also agree that the data doesn’t support parental investment theory. The link between parental investment and reproductive behavior is not always predictable. In many species, males can be just as choosy as females, and females as sexually competitive as males.
But in Roughgarden’s view, this challenge stops short. Rather than gain equal rights for females within sexual selection, Roughgarden seeks to do away with the theory that she believes nature’s sexual diversity has rendered obsolete. Beyond the categorizations of male and female, or even homo- and heterosexual, Roughgarden cites numerous examples of species that do not fit into what she calls the “gender binary.” Pointing to the prevalence of hermaphroditism, multiple genders, and species that change sex during the lifecycle, she believes that the real story of sexual behavior is being stifled by sexual selection theory. “The facts speak for themselves,” she says, “and the facts are that biologists have been covering up the extent of certain sexuality, homosexuality, and all kinds of gender and sexuality expressions.” She sees the theory of sexual selection as a rigid framework that highly complex behaviors have been needlessly shoehorned into. “I think it’s pretty clear that there are no known established cases where sexual selection is true,” she says. “There are lots of papers that invoke sexual selection after the fact, to rationalize the behavior, but they don’t test it and that’s in part because they don’t have an alternative.”
In seeking to formulate her own alternative, Roughgarden attacked sexual selection from another angle, as well. As research in previous decades found females to be just as competitive and just as promiscuous as males, the “battle of the sexes” resurfaced in the form of sexual conflict: an evolutionary “arms race” where males and females with conflicting ideal reproductive strategies continually evolve new traits to defeat the other sex. With new data on phenomena like “killer sperm” making headlines, an antagonistic relationship between males and females had been adopted as a major driving force in sexual selection. As Roughgarden has described it, sexual selection assumes “that the male-female relationship begins with sexual conflict from which cooperation may be derived.”
Taking a different approach, Roughgarden’s theory proposes that “the male-female relationship begins with shared investment that may devolve into conflict.” Rather than males and females being forced to reconcile conflicting fitness strategies, her “social selection” theory suggests that males and females cooperate to ensure the survival of the greatest number of offspring possible. Using cooperative game theory, a set of mathematical models used in economics and applied mathematics, Roughgarden hypothesizes that the individual male’s and female’s actions involve obtaining and exchanging direct benefits to increase the number of offspring successfully reared. In this way, the starting point for the theory is cooperative investment as opposed to competitive advantage. The mathematics of the game are complex—decisions are made on the basis of threats, promises, side payments, and alliances—but Roughgarden describes it simply as, “viewing heterosexual mating as similar to funding a joint investment.” Applying this theory, Roughgarden suggests an alternative explanation for Darwin’s original promiscuous-male-coy-female scenario: Females have greater control of the offspring investment, forcing the male to acquire multiple partners in order to ensure that some survive. In this way, promiscuity becomes a strategy of last resort.
A few months after Roughgarden’s 2006 review presented her theory, Science published 10 letters signed by 40 different authors refuting it—an unusual number of responses for any paper. All of the letters disagreed with the idea of abandoning sexual selection. But at least two letters, signed by 21 and 24 authors, respectively (including 14 who signed both), argued for more than the continued use of sexual selection theory. They argued that Roughgarden’s “social selection” theory is not an alternative at all, but rather an idea already covered within sexual selection theory. Though Roughgarden responded to these allegations in Science, the criticism remains. Tim Clutton-Brock of the University of Sussex says, “I’m reluctant to say [Roughgarden’s model] has no merit, but I’m not convinced it explained anything that wasn’t already explained by sexual selection.” Meanwhile, Roughgarden maintains, “There is no room for cooperative game theory in sexual selection theory…[my theory] is not explained by sexual selection theory because sexual selection theory is demonstrably wrong.”
For the moment, the issue is at an impasse.
But possibly the most damning criticism Roughgarden receives is that she’s deviating from science, and allowing a personal “gay agenda” to influence her take on the data. Indeed, her public advocacy—including a “political agenda for transgendered people” included in Evolution’s Rainbow—isn’t helping her reputation among scientists. “She is concerned about the implications outside of science, and it would be even more so because she’s been on the receiving end of the implications of that,” says recent graduate student Erol Ackay. “But I don’t think that’s a valid criticism of the science.” Carol Boggs, a biologist and colleague at Stanford for more than 30 years, says, “She’s always had a concern about social issues and political issues, and I think many scientists at one level or another are concerned about social and political issues. It’s just that we’re used to having scientists be concerned about environment issues, or something like that. We’re not used to having scientists who are coming from biology being concerned about gender issues.”
Many consider the debate over sexual selection to be one of the most heated exchanges currently taking place in the life sciences, and it seems that many are optimistic about the results. In one of the letters responding to the Science review, Jeffrey Stewart of the Aeri Park Institute wrote, “The game theory idea might be better argued…nevertheless, the use of game theory and the associated mathematics of reproductive behavior research could prove extremely useful in this field.” In a Science review published at the end of last year, Clutton-Brock wrote, “Roughgarden’s views are unusual, but it is clear that the mechanisms underlying sex differences in reproductive competition and the traits associated with them are both more diverse and more complex than was initially realized. In the wake of Roughgarden et al.’s review, both the exceptions to the basic structure of sexual selection theory and the operation of sexual selection in females deserve further attention.” Gowaty says she disagrees with Roughgarden’s game theory approach, but she also says, “I am always delighted when controversial ideas, even ones that I’m not in agreement with or ones I think are silly, see the light of day. I always hope that where there is heat, some light might be generated.”
In this case, Roughgarden’s controversy may end up contributing to the field in ways that neither she nor her critics predicted. Only more research will determine if there’s anything to “social selection,” or whether sexual selection still provides a valid model. In the immediate future, Roughgarden has no plans to slow down. Still working to make her research relevant to different fields, she gives talks all over the country at the invitations of psychologists, social scientists, and even philosophers. Currently, she’s in the midst of revising the sequel to Evolution’s Rainbow, which will debut in early 2009. Titled The Genial Gene: Deconstructing Darwinian Selfishness, it challenges Richard Dawkins’ famous selfish gene metaphor, asking whether the gene-centered view of evolution explains sexual behavior. Confronting another basic tenet of the field will almost certainly cause more controversy; Roughgarden has already been filmed with Dawkins for the BBC. Let’s hope the controversy leads to insight.
Sandya Viswanathan is a documentary filmmaker whose projects have aired on The History Channel, National Geographic Channel, and PBS. She resides in New York City.
