The study, on fruitfly mating, was done in 1948 by geneticist A.J. Bateman. Bateman showed that the male insects' strategy was to mate with many females, whereas the females' strategy was to be discriminating in their choice of partners. Male reproductive success, in other words, correlated positively with number of mates, but female reproductive success did not.

Now, ecologist and evolutionary biologist Patricia Gowaty and her colleagues Yong-Kyu Kim and Wyatt Anderson have repeated that study. They conclude something startling: Bateman blew it.

Before I explain where they say Bateman went wrong, I need to show how Bateman's conclusions rippled far beyond the scholarly world of fruitfly sex. His findings — promiscuous males, choosy females — seemed to strike a cultural chord. Afterbiologist Robert Trivers cited it in a key 1972 paper on parental investment, the "Bateman principle" turned up everywhere. In my own field of primate behavior, for instance, field researchers expected to see (and thus often did) male primates with highly active sex lives and females who were coy, verging on sexual passivity.

And don't think that humans were left out of this picture. We've all heard it, right? When some big-name male public figure sleeps around, and cheats on his wife, isn't there always someone ready with an evolutionary explanation about vigorous male seed-sowing?