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.”