Is warfare linked to evolution?
- December 30, 2014
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Among an eastern African farming people, males who participate in livestock raids in youth may enjoy greater long-term “reproductive success,” a study has found.
The results could feed into a longstanding debate over whether warfare is a product of evolution. Evolutionary theory holds that characteristics of a species take root because they enhance survival and reproduction. Over generations, this causes advantageous features for an individual to spread throughout a population, while unhelpful characteristics die out.
In the new study, published in the journal Proceedings of the National Academy of Sciences this week, Luke Glowacki and Richard Wrangham of Harvard University traced the number of wives and children of 120 male members of the pastoralist Nyangatom people of Ethiopia and South Sudan.
In the short term, the authors found, men who engaged in livestock raids didn't have more wives or children than non-raiders. This suggests that captured livestock aren't directly used as leverage for marriage opportunities-rather they're used by existing family members, the researchers said.
On the other hand, “elders who were identified as prolific raiders in their youth have more wives and children than other elders,” the authors wrote. “Our results suggest that in this cultural context raiding provides opportunities for increased reproductive success over the lifetime.”
“The causes of warfare in small-scale societies continue to be debated,” the authors added. “Most anthropological explanations have focused on causes that ignore the individual benefits warriors sometimes receive for participation.”
However, they added, “evolutionary anthropologists have commonly argued that warriors may receive fitness benefits,” or advantages that enhance their reproductive opportunities. “This hypothesis has a contentious history, in part because of concerns that a positive association between warfare and reproductive success may suggest biological” tendencies toward violence.
Glowacki and Wrangham also examined whether raiding and reproduction among the Nyangatom might be only coincidently related because both are related to a third factor-the man's number of older siblings, which may enhance resources to leverage marriage opportunities. But the researchers concluded that this wasn't the case.
Source : http://www.world-science.net