Different roots. This skull from Baja, Mexico, casts doubt on the theory that all early Americans came from north Asia.

Early Diversity in the Americas

A new analysis of ancient skulls from Mexico's Baja California bolsters the case that the first people to settle in the Americas came from more than one part of the world.

Some 12,000 years ago, the ancestors of today's native Americans migrated from North Asia via a land bridge across the Bering Strait that was later submerged when the glaciers melted. Indeed, most modern native Americans share many physical features with north Asians. But a growing mystery has arisen because the oldest skulls that have been found in North America, such as the 9000-year-old Kennewick Man and even older "paleoamericans," bear no resemblance to today's native Americans. At least some of the first Americans, it would seem, came from somewhere other than north Asia. The new find, reported in the 4 September issue of Nature, deepens the intrigue.

Anthropologists from Spain, Mexico, and Argentina describe newly discovered skulls from people who inhabited the Baja peninsula about 2000 years ago. The team, headed by Rolando González-José of the University of Barcelona, took detailed measurements of 33 skulls found on the tip of the peninsula and stored in two museums in Mexico and compared them to skulls from around the world. Despite their relative recency, the Baja skulls bore little resemblance to the skulls of Aztecs and other native Americans. They most resembled paleoamerican skulls, which have features in common with some South Asians and Pacific islanders.

This, say the authors, supports the notion that not all the earliest Americans came from northern Asia, but some--descendants of people who were also ancestors to Australian aboriginals--came around all the way from southern Asia. The authors speculate that being geographically isolated by a desert helped the early Baja inhabitants retain their resemblance to ancient forebears.

The paper adds fuel to a "fiery debate" about the settling of the Americas, says Tom Dillehay of the University of Kentucky, Lexington. But he and others have reservations. "By itself, cranial morphology is not something you want to go to the bank with," says Douglas Meltzer of Southern Methodist University in Dallas, Texas. He and Dillehay both say that genetic data are needed to prove that the Baja people represent a separate population from American Indians. Even so, Dillehay says, the find adds to evidence that the current theory on how the Americas were peopled may need revision. "It's looking more and more as though there were several different founding populations, arriving from different places."

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