for National Geographic News
At least two distinct groups of early humans colonized the Americas, a new study says, reviving the debate about who the first Americans were and when they arrived.
Anthropologists Walter Neves and Mark Hubbe studied 81 skulls of early humans from South America and found them to be different from both modern and ancient Native Americans.
The 7,500- to 11,000-year-old remains suggest that the oldest settlers of the Americas came from different genetic stock than more recent Native Americans.
Modern Native Americans share traits with Mongoloid peoples of Mongolia, China, and Siberia, the researchers say.
But Neves and Hubbe found that dozens of skulls from Brazil appear much more similar to modern Australians, Melanesians, and Sub-Saharan Africans.
Neves and Hubbe describe their findings in this week's edition of Proceedings of the National Academy of Sciences.
Who Was First?
The scientists examined 81 skulls unearthed over many decades in Brazil's Lagoa Santa region. They represent the largest collection of early American remains, many of which had to be tracked down in European museums.
These "paleoamerican" or "paleoindian" skulls feature projecting lower jaws, broad noses, and broad eye sockets, the researchers report. These traits are unlike those of modern Native Americans.
This strongly suggests that those early Americans were in fact a distinct group, Neves says.
He adds that the group could have crossed the Bering Strait land bridgethe once-exposed landmass between Siberia and Alaskathousands of years earlier than the Siberian populations who are believed to be the ancestors of modern Native Americans.
Other paleoamerican skulls have displayed similar traits to the Lagoa Santa skulls, which has led to controversy and differing theories about how and when the Americas were settled.
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