Nicky Lewis
4 September 2003
Source: SciDev.Net

The question of who colonised the Americas has been hotly debated for decades. Recent work suggests there have been two different waves of migration: the first from South Asia and the Pacific Rim, and the second from northeast Asia and Mongolia. Most modern Amerindians are believed to descend from the latter group.

But research published in this week's Nature suggests that a small group of Mexicans shares its ancestry directly with the first settlers. A team of researchers from Argentina, Mexico and Spain analysed the shape and structure of 33 'modern' skulls taken from the tip of the Baja peninsula in Mexico.

They found that these skulls bear closer anatomical similarity to southern Asian skulls than to other modern Amerindian remains. The authors suggest that the early inhabitants of the Baja peninsula may have become geographically isolated after the Ice Age, and therefore remained genetically distinct from northeast Asian migrants who subsequently settled on the mainland.

In a related article in Nature, Tom D. Dillehay from the University of Kentucky, United States, notes that the new research reinforces a more complex view of American ancestry than is traditionally put forward. "Slowly, we are realising that the ancestry of the Americas is as complex and as difficult to trace as that of other human lineages around the world," he says.

Reference: Nature 425, 23 (2003) / Nature 425, 62 (2003)

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