For decades it has been believed that the first peoples to populate North and South America crossed over from Siberia by way of the Bering Strait on a land-ice bridge.
However, a new study examining the largest collection of South American skulls ever assembled suggests that a different population may have crossed the bridge to the New World 3,000 years before those Siberians.
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The skulls belonging to the earliest known South Americans--or Paleo-Indians--had long, narrow crania, projecting jaws, and low, broad eye sockets and noses. Drastically different from American Indians, these skulls appear more similar to modern Australians, Melanesians, and Sub-Saharan Africans.
This indicates that these skulls--which date to 7,500 to 11,000 years ago--were not merely anomalies but rather were the majority, supporting the hypothesis that two distinct populations colonized the Americas.
Not sure where the 3,000 years figure came from. It doesn't say in the article. We'll attempt to find the original paper and check that out.
This ought to spur some debate about the origin of the craniometric traits they use to classify skulls to different populations. Generally, ancient skulls are compared to references collections derived from modern specimens. Given a 13-20,000 year space of time, the question of whether the configuration observed in these South American skulls arises from actual ancestor-descendent relationships, or perhaps a parallel evolution that just happens to make these skulls group similarly to the moden Aussie-Melano-African ones. Generally speaking, using a suite like this ought to negate that sort of thing, but it will no doubt be an issue.