Did first Americans make a 10,000-Year Pit Stop on Beringian land bridge?
It has long been debated whether the first human settlers of the New World arrived by walking over a land bridge across the Bering Strait from Siberia to Alaska, or whether they arrived by sea from southwest Europe millennia earlier, the so-called Solutrean hypothesis. Now a new study has suggested that the first human settlers arrived on foot from Siberia, but took a ‘pit stop’ of ten millennia on the 1,000-mile-long Beringian land bridge before making the move to Alaska.
The new study, published in this week's issue of the journal Science, reports that sediment cores from Alaska and the Bering Sea support genetic evidence that the first human settlers of the New World spent thousands of years inhabiting Beringia, a theory known as the Beringia standstill hypothesis.
Scientists once thought this vast tract consisted mostly of tundra steppe, a treeless environment incapable of supporting a large human population. But paleoecologists—scientists who study ancient environments—have found that sediment samples contained fossils indicating that Beringia's tundra steppe also contained woody plants, which could have been used to start fires, build shelters, and as cover for animals that humans could have hunted for foot. This suggests the land bridge was much more habitable than previously believed.
Dennis O'Rourke, an anthropological geneticist at the University of Utah in Salt Lake City, said that these results are consistent with genetic studies showing that the DNA of Native Americans is distinct from that of their Asian ancestors. Using knowledge of DNA mutation rates, the researchers concluded that the people who migrated to the New World must have split from their Asian ancestors about 25,000 years ago. Taking into account the popular view that people reached the Americas 15,000 years ago, O’Rourke and colleagues conclude that they must have settled in the Beringian land bridge for 10,000 years.
However, there are two major problems with this conclusion. The first is that archaeological evidence has been found in America that is much older than 10,000 years. "We definitely have some stuff here in the east of the United States that is older than anything they have in the west," said anthropologist Dennis Stanford of the Smithsonian Institution, a proponent of the out-of-Europe model. "They've been reliably dated to 20,000 years ago," too early for migrants from Beringia to have made the trek, he said, and strongly resemble Solutrean artefacts.
The second problem is that no archaeological evidence of human settlements has ever been found in the Beringian land bridge. O'Rourke claims that this is because many lowland areas become flooded with glaciers melted and the sea level rose. However, he neglected to mention that at least half of Beringia is still above water, so this explanation is not convincing enough. "If people were there for 10,000 years, you'd surely see evidence for them by now," said David Meltzer, an anthropologist at Southern Methodist University in Dallas.
Remote survey technologies are now advanced enough to allow researchers to peer beneath the water and sediment to identify areas that show signs of past habitation. It is hoped that this could help resolve this enduring debate.