Guys may unknowingly be leaving their mark on the world: Scientists from the University of New South Wales in Australia have taken on what was widely considered to be the discredited theory of telegony—the idea that a woman's children might resemble not just her current sexual partner, but a previous one as well—and shown evidence of it in flies, Phys.org reports. The study, published in the Ecology Letters journal, first mated male flies whose diets had been specially engineered with female flies that weren't yet able to reproduce; in the second round, researchers waited for the females to mature, then mated them with a new guy. The results: Offspring size was determined by the mother's first partner, not by the father.
The telegony concept goes back to Aristotle, notes the Telegraph, and may have had an impact on Greek mythology (many heroes feature a godlike dad and a regular human dad). While modern genetics studies seemed to have put the kibosh on that idea, according to the Telegraph, scientists in the UNSW study believe that some of the original male partner's semen may absorb into the female's immature eggs and hang out until she's mature enough to be fertilized by another male. So what does this mean for humans who didn't, er, stay with their first love? "Things that were thought impossible previously might indeed turn out to be not so far-fetched after all, [though] I think it's impossible to say … without further studies in a more related species like a mouse," a cellular and molecular pharmacology professor at Oxford tells the Telegraph. (Moms with gene mutations may one day be able to have "designer babies" using three-parent IVF.)