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.
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