Discovery

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Archive for the ‘Archeology’ Category

Some discoveries come wrapped in mystery

For more than two decades, researchers have wrestled with something akin to a unified theory of archeology. Put forth by Colin Renfrew, the “farming-language dispersal hypothesis” suggests that farming helped spread language and culture through Europe, Africa, and Polynesia.

The claim, formalized with Australian Peter Bellwood, was appealing in its elegance, if not a bit brash. As Renfrew wrote in the 1996 The origins and spread of agriculture and pastoralism in Eurasia, the ancient distributions of language and farming are so closely related “that an adequate understanding of world genetic diversity and its origins will scarcely be possible without an insight into this fundamental relationship.”

Washington State University molecular biologist Brian Kemp has spent several years extending the hypothesis into the Southwest and Mesoamerica, between central Mexico and Central America. Scholars have long noted a relationship between past and present people in the two regions, the farming of maize, and shared words of the Uto-Aztecan languages.

Writing first for his UC-Davis doctoral dissertation and now the latest Proceedings of the National Academy of Sciences, Kemp explored the possible genetic connections that might be another brick in the wall supporting Renfew’s hypothesis.

Using DNA samples from Uto-Aztecan speakers in the two regions, Kemp looked at both mitochondrial DNA, which is passed down from mothers, and Y-chromosomal DNA, which is held only by men.

Dachalan maize photo courtesy of Flickr. Click image to see photostream.

The mitochondrial DNA doesn’t do much for Renfew’s hypothesis. Women were more closely related to non-Uto-Aztecan speakers in their areas. This, Kemp says, “suggests that no matter which way the language spread, it didn’t spread with females.”

But when he looked at the male DNA, he saw genetic links between men in the two regions. He can’t say which way their genetic material spread. However, he says, “it seems to have been spread by the males, not the females.”

Leaving, well, a mystery. It’s easy enough to imagine male farmers branching out, taking their farming practices, language and genetic variation with them. But a significant expansion of people would seem to need both sexes to reproduce and last more than a generation.

“In the end,” Kemp says, “it’s kind of a frustrating conclusion.”