For males, monogamy can have evolutionary benefits

Mon Jul 29, 2013 3:51pm EDT
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By Sharon Begley

NEW YORK (Reuters) - Whenever a public figure cheats on his wife, pundits can be counted on to trot out the tired old claim that males are simply wired by evolution to be promiscuous.

Two studies released on Monday beg to differ. By sticking to one female, they conclude, males of many species, especially primates, can increase their chances of siring many offspring who survive long enough to reproduce - the key factor in determining whether a particular behavior survives the brutal process of natural selection.

In fact, the evolutionary advantages to males of being monogamous are so clear that the two studies reached competing conclusions about which benefit is greater for males. According to research published in the Proceedings of the National Academy of Sciences, protecting the lives of his offspring was the paramount benefit of monogamy.

Separate findings published in the journal Science said that keeping his mate faithful provided the greatest evolutionary edge.

Both studies addressed a conundrum: because male mammals can sire so many more offspring per breeding season than females, it would seem that mating with only one female would be less adaptive for a male than spreading his seed widely.

The PNAS paper, which analyzed 230 species of primates, concludes that protecting the kids is the greatest benefit of male monogamy. By sticking close to his mate a male reduces the risk of infanticide. Although the study examined only nonhuman primates, that reasoning has resonance in people, too, where children who grow up without a father in the household are more likely to die in childhood, according to government statistics.

"This is the first time that the theories for the evolution of monogamy have been systematically tested, conclusively showing that infanticide is the driver of monogamy," said anthropologist Christopher Opie of University College London, lead author of the PNAS paper, which analyzed 230 species of primate. "This brings to a close the long-running debate about the origin of monogamy in primates."

Not so fast, according to authors of the Science paper. Zoologists Dieter Lukas and Tim Clutton-Brock of the University of Cambridge examined the social structure of 2,545 species of mammals, of which 9 percent are socially monogamous. That was defined as a system in which a male mates with only one female and they "usually stay together until one dies," Lukas told reporters on Monday.   Continued...