Tuesday, February 19, 2008

How the Americas may have been settled

via Livescience, a little more regarding the new theory of how early American natives settled the New World. While it does not change the early notion of people migrating over the Bering Strait land bridge during the last global Ice Age, it certainly does modify it substantially. In short, the new idea is that the migration occurred in three phases.

The first phase was one in which people migrated into the area of the land bridge, called Beringia, around 40,000 years ago, following migratory game. While not sedentary, these early hunters more or less stayed in this region for around 20,000years as the routes through the Rocky Mountains were blocked by the substantial glaciation taking place at that time. As these glaciers began to melt and passes opened through the mountains and along the coast, people migrated south approximately 15,000 years ago. As the glaciers continued to melt, the Beringian "homeland" slipped under the sea 10-11,000 years ago. So how did the researchers reach these conclusions? DNA.

"DNA allows scientists to deduce the history of populations. For instance, mutations that all New World populations have in common with each other and no one else means they share a common ancestry, suggesting there was just one wave of migration into the Americas, as opposed to several unrelated waves. However, the molecular evidence was confusing as to when this wave of migration took place. DNA accumulates mutations over time, serving like a clock, but some DNA suggested people came to the New World about 13,000 years ago, while other sequences hinted at 30,000 or more years ago."

The long wait on the doorstep of the Americas neatly explains both the DNA evidence and the apparent lack of artifacts from the earliest time period - even if the relatively small population of this group of prehistoric people did leave any artifacts behind, they are likely now underwater. Obviously, conditions today in this region of the world make finding such artifacts a daunting task, one which very few researchers (if any) have attempted to tackle.

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