The first Americans to cross from Asia to the New World may have been trapped there by climate change. The story of the Native American ancestors walking across the Bering Strait land bridge has been known for some time. But in a new twist, it may be they were trapped there when the climate changed and glacial melt flooded the bridge.
Genetic proof has been given that Asian populations crossed the area known as Beringia around 25,000 years ago. But anthropologist Dennis O’Rourke of the University of Utah has recently released a study which claims that these migrants actually lived in Beringia for around 10,000 years. This comes from the analysis of Mitochondrial DNA which shows that the populations didn’t reach North American until around 15,000 years ago.
The theory he is discussing is called the Beringia standstill hypothesis and was discussed in the journal Science last month. It says that Beringia was a home to them for many generations, which explains the difference between the leaving Asia time and the settlement of North America time. O’Rouke continues to hypothesize that Beringia was not a barren steppe between the continents, but a normal area of land inhabited by trees and shrubs and animals such as bison and mammoth.
Other DNA evidence also seems to suggest that the ancestors of some of the northern populations such as the Inuit came in a separate wave of settlers in a later migration.
In fact, Beringia may have been a huge landmass. During the last ice age, from 28,000 to 18,000 years ago, the ice sheets reached down to Alaska and sea levels were 400 feet lower. This meant that Beringia was around 1000 miles from north to south and 3000 miles from Siberia to the Mackenzie River in Canada.
It is also believed that temperatures were similar to the area today, especially in the lowland areas. Winter would have been cold but no worse than currently experienced today.
Insects and traces of plants have been uncovered, back in the 1930s by Eric Hulten, a Swedish Botanist, in the sediment beneath the Bering Sea which gives an indication as to what the landscape was like. The people who lived there could use the woody shrubs for fire and the animals to hunt for food.
The main problem with the theory is that no evidence of human settlements has been found in the Bering Sea area. O’Rouke suggests that due to people occupying the lowland areas primarily, these would have been the first to flood when sea level rose. This would have destroyed evidence of habitation.
End of the Ice
When the ice began to melt, the barrier which originally separated America from Beringia melted and allowed migrants to move into it. But the rising sea levels which came with the melting ice also meant that they were cut off from their homeland and their place of origin in Asia.
The Beringia theory also fits in with a recent genetic study which stated that all Native American populations had a common ancestry with the Clovis people. This is based on studies of a young boy whose remains have been analysed.
The Clovis Culture was a prehistoric Indian culture named for sites at Clovis in New Mexico. They are considered the ancestors of both north and South American populations and several sites have been found across North America containing their remains.