Who were the “first” Americans?

It’s an age-old question with conflicting answers. Archaeological evidence shows that humans migrated south of the Canadian ice sheets some 15,000 years ago. One theory says a single population of modern humans migrated from southern Siberia across the Bering Land Bridge (Beringia) around 30,000 years ago, and could have crossed over to the Americas as early as 16,500 years ago.

For decades, it was commonly held that the Clovis hunters — a people who seemingly emerged and disappeared in the blink of time— were the first inhabitants of the Americas, but that has been disproved in recent years thanks to DNA-based archeology. A more contentious theory argues that the first Americans did not cross by Beringia at all, but by boat across the ocean. Little evidence exists to support this claim.

Last week, a group of evolutionary biologists and geneticists have released what could be a debate-settling scientific report in Science magazine.

The team compared genome data from 110 modern Native Americans and 23 who died between 200 and 6,000 years ago, and then compared the DNA to an additional 3,000 people from around the world. In conclusion, they found that “...all present-day Native Americans...entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (KYA), and after no more than 8,000-year isolation period in Beringia.”

How concrete is this finding?

“For a long time,” Carlos Bustamante, PhD, one of the project’s lead authors, told Stanford University’s Scope blog. “We’ve sought to understand the genetic history of the first people to populate the Americas and how they relate to modern day populations. This project brought together a large interdisciplinary team and amassed the largest data set to date on this problem. We found strong evidence for a single major wave and subsequent divergence of the founding population.”

The grassy plains of Beringia were swallowed by rising seas over 10,000 years ago. But the new genetic analysis still traces the original Native Americans through this 600,000-square-mile passage of land.

Their research further confirmed previous studies about the ancestral American gene pool. Upon arrival, the first Americans basically divided into two basal genetic branches — one that is now scattered across North and South America, and the other that is limited just to North America. Some Native Americans share genetic ancestry with today’s East Asians (including Siberians), and even — albeit remotely — with Australo-Melanesians.