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Male dominance is no guarantee of genetic success

Genghis Khan spread his seed so liberally that nearly a tenth of men now living in the former Mongolian empire trace their ancestry back to the 13th-century warrior. However, a new analysis suggests that most socially dominant males contribute no more to the genetic pool than do their supposed inferiors.

"An individual really doesn't have the opportunity to set up things so their genetic information pervades the gene pool a long time in the future," says mathematician Joseph Watkins, of the University of Arizona in Tucson. "It could happen because life is chaotic."

Theories on how genes flow through populations of organisms generally support this idea, which has been dubbed neutrality. But some anthropologists argue that cultural dominance can seal a man's legacy. For instance, a rich and powerful father can ensure the status of his sons and grandsons.

Back in time

To determine whether dominance could last more than a couple generations, Watkins and a team of anthropologists and geneticists sifted through the DNA of 1269 males from 41 Indonesian communities.

They honed in on stretches of the male-inherited Y chromosome that change little from generation to generation. This allowed Watkins' team to peer back more than 3000 years.

Their search paid no attention to genetic traits that might offer an evolutionary boost and instead focused on "junk" DNA that flows exclusively from father to son.

Out of 41 communities, from Bali to Borneo to mainland Indonesia, only five showed evidence of long-term dominance by a few male lines.

Three of those communities were in Sumba, a remote island where males are polygamous and clans vie for status and resources. The genetic patterns seen in males from the other two communities could be explained by an influx of foreign workers in one case, and a recently settled village in the other.

'Equal opportunities'

Of course, Genghis Kahn proves that some powerful males can ensure their lineage - if not through prosperity, then promiscuity - but such men are rare, Watkins says.

"If I were to take 100 random Mongolians and follow their family lines, I wouldn't have seen anything special."

Peter Underhill, a population geneticist at Stanford University, agrees that cultural traits that flow exclusively from father to son, such as wealth and property, are unlikely to last.

"Evolution is an equal opportunity system. No single group is going to persist as the dominant group for very long before something changes," says Michael Hammer, a co-author of the study.

Wars, climate change, and diseases have all sent dominant males careening off their pedestals, he says.

Journal reference: PNAS (DOI: 10.1073/pnas.0710158105)





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