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An Evolutionary Explanation for Altruism: Girls Find It Sexy

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Marie Killen

Girl giving twin medicine

One of the big unsolved mysteries in evolutionary theory is why creatures are altruistic. Selflessness doesn’t seem to be one of those qualities that ensure survival of a bloodline, since, by definition, it means acting against oneself. And genes, as Richard Dawkins has famously suggested, are pretty selfish. So, how come we still have customers jumping over fast-food counters to save an employee from a gun-wielding nutjob? Or ants that raise other ants’ children? A new study in the British Journal of Psychology makes the case that it’s because some females of the species are genetically predisposed to prefer altruistic mates. (More on Time.com: 5 Little-Known Truths About American Sex Lives)

The study, a summary of which was published on Science Daily, asked identical and fraternal twin sisters, questions about their own selfless actions and how desirable they found noble or sacrificial acts performed by others. The participants were not aware of what the study was testing.

“Identical twins share the same genes 100%, while non-identicals have a 50% chance of sharing any given gene,” says lead author Tim Phillips, who was a graduate student at the University of Nottingham when he did the research. If the identical twins came up with the same answers more often than the fraternal twins did, then it’s more likely that genes were the reason. “And that’s exactly what we found,” says Phillips.

Of course, altruism wasn’t attractive to everyone. But because some people are genetically predisposed to find selfless men hot — perhaps assessing that they’re more likely to help with the vicissitudes of bringing up kids — that trait may have been able to survive in the human gene pool through generations. “According to our theory females would have often had a limited choice of quality, altruistic males due to the cost of child-rearing so there would have been competition  to attract and retain such males,” says Phillips. “But this is at present informed speculation.” (More on Time.com: Photos: Love Ever After)

There are several other theories about altruism, but one of the more intriguing ones is that it’s all relative. A person or creature will do something selfless if the act still saves enough of its own genetic material — say, the amount carried in a couple of brothers or a half-dozen cousins. This is why it can be that many sterile female insects spend their allotted days on this planet raising somebody else’s children, instead of loafing about sipping dandelion nectar or seeking out insectile nooky.

One biologist developed a formula for how much genetic material would have to be to saved in the act of altruism for it to be worthwhile. But the academic equivalent of fisticuffs broke out recently when two Harvard scientists recently suggested that the formula actually doesn’t work for ants.

So, it’s safe to say we still don’t understand exactly why, evolutionarily speaking, people regularly do things that go against their own interests. But, as if we needed science to tell us, it’s partly so they can get girls.

NOTE: This story originally referred incorrectly to Dr. Phillips title. Time regrets the error.

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