For decades, most evolutionary biologists based their understanding of female mating choice on a paper that turned out to be incorrect. The idea that females (including human ones) always choose the single "best" mate, rather than choosing promiscuity? Wrong.
Photograph of bonobos by Sergey Uryadnikov via Shutterstock
Today, 3 Quarks Daily's annual science prize was announced, and the winning essay is about why evolutionary biology was so mistaken about female mating choice for so long. Science historian Eric Michael Johnson explains what went wrong — and how scientists have demonstrated a pattern of "pragmatic" female promiscuity in many animals over the past 40 years.
In 1948, a balding and near-sighted English geneticist by the name of Angus Bateman published one of the most influential papers ever written on the evolution of sexual behavior. After studying patterns of inheritance among offspring in the common fruit fly, Drosophila melanogaster, Bateman concluded that the division between ardent males and coy females was "an almost universal attribute of sexual reproduction" across the entire animal kingdom. Bateman reasoned that, because females produce dramatically fewer eggs than males do sperm, and because eggs were physiologically more expensive, female reproductive success would not increase by mating with more than one male. Instead, females should focus on choosing the "best" male that they could and then directing their energy toward raising offspring. On the other hand, males who mated with multiple females would be expected to greatly increase their own reproductive success because the benefit outweighed the cost of production. Sex, like economics, was a question of quantity versus quality.
There was only one problem: Bateman got it wrong. In June 2012, UCLA biologist Patricia Gowaty and colleagues replicated Bateman's study only to find that he had come to faulty conclusions because his methodology was severely flawed. Without modern genetic analysis at his disposal, Bateman conducted his trials with males and females of known mutant strains whose offspring could be easily identified. However, he counted only offspring that had two mutations—one from each parent—in order to be certain of a given fly's reproductive success. This approach resulted in a biased sample because flies with some mutations were less likely to survive than those with others. In the end, the premiere study on sexual selection—which had been cited by more than 2,000 peer-reviewed papers and textbooks—contained a fatal flaw that would have been easily identified had the study been replicated sometime in the preceding 64 years. How could this happen?
Don't miss out — read the entire award-winning essay over at Slate. It's a great exploration of the way that scientific theories are always changing over time as we gather new evidence.