martes, 3 de enero de 2017

The first Americans: How and when were the Americas populated?

Earliest evidence of humans in the Americas. Credit: K. Cantner.

Archaeologists used to have a tidy story to explain the earliest peopling of the Americas: During the last ice age, when sea levels were much lower, a band of intrepid travelers walked from East Asia, over the Bering land bridge, and into Alaska. From there, they followed an ice-free corridor east of the Canadian Rockies south onto the megafauna-rich plains, eventually spreading throughout North and South America by 11,000 years ago and leaving a trail of finely shaped “Clovis” spear points in their wake.

But the story is not so simple. The once-dominant “Clovis First” Hypothesis has been overturned in recent years by discoveries of an array of pre-Clovis tools and campsites throughout North and South America that date to as early as 16,000 years ago. But how is it that people colonized the Americas so much earlier than once thought? From where did they come? And what routes did they take?

Recent work investigating the eastern slope of the Rockies suggests that an ice-free corridor in this area may not have opened until about 13,000 years ago, thousands of years later than the earliest settlement sites now known in North and South America. That leaves a coastal route as the most likely passage, but which coast the earliest settlers followed is up for debate. [...] EARTH Magazine