Geneticist A.J. Bateman did an experiment in 1948 which showed that, in mating fruitflies, 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.

You've seen casual invocations of this study everywhere. Heck, the entire field of evolutionary psychology was created on this "Bateman principle" that all sexual conduct is grounded in solid science. And it snowballed. Once evolution could explain one aspect of behavior, it could explain anything, which is why the 21st century is littered with claims that what genetics can't explain, like what candidates people vote for, epigenetics can.
 
There's just one problem, say a group of researchers who duplicated the study so fundamental that almost no one duplicates it - Bateman was wrong. The conclusion even violated Mendel's Laws of Genetics, the researchers wrote to Barbara King at NPR:
Bateman's method over-counted the number of offspring for fathers, because there were more single-mutant offspring that had dad's mutation than mom's mutation. It's elementary, and essential in sexual species, that the number of offspring having Dads must equal the number with Moms.
Some caution is in order. Once week someone is claiming to debunk Einstein and arXiv is littered with papers mathematically making time travel possible. But woo anthropology claims about how sexist the conclusion was don't have much credibility in science either. Will the new study by evolutionary biologist Patricia Gowaty and colleagues Yong-Kyu Kim and Wyatt Anderson survive scrutiny?  Stay tuned.

Sorry boys, the double standard may be double debunked and you'll have to stop being hound dogs and saying evolution made you do it. And double sorry, evolutionary psychologists, for making you get real jobs.

Promiscuous Males And Choosy Females? Challenging A Classic Experiment by Barbara J. King - NPR