And there's no covering up even ancient sexual dalliances: the guys most successful in sowing wild oats passed on the proof in their genes.
By using those genetic smoking guns, researchers at the University of Arizona in Tucson have developed new insights into ancient mating and migration patterns in humans.
Men and women differed in their participation in reproduction, the researchers report. More men than women get squeezed out of the mating game. As a result, twice as many women as men passed their genes to the next generation.
"It is a pattern that's built up over time. The norm through human evolution is for more women to have children than men," said Jason Wilder, a postdoctoral fellow in UA's Arizona Research Laboratories and lead author on the research articles. "There are men around who aren't able to have children, because they are being outcompeted by more successful males."
Co-author Michael Hammer, a research scientist in UA's Arizona Research Laboratories, said, "We may think of ourselves as a monogamous species, but we're coming from an evolutionary history that's probably slightly polygamous. If we're shifting toward monogamy, it's so recent it hasn't left an imprint on our genome."
Or the same reproductive behavior is continuing, but in a culturally accepted fashion, Wilder said. "The modern version that we generally don't find offensive is that men tend to remarry and have more children much more often than women do."
The team's research also overturns the long-accepted idea that, on average, women's genes traveled farther from their birthplace than did men's. That idea was based on a common marriage practice called patrilocality, wherein women tended to move from their natal village to their husbands' village.