More than 15,000 years ago, humans began crossing a land bridge called Beringia that connected their native home in Eurasia to modern-day Alaska. Who knows what the journey entailed or what motivated them to leave, but once they arrived, they spread southward across the Americas. The prevailing theory is that the first Americans arrived in a single wave, and all Native American populations today descend from this one group of adventurous founders. But now there’s a kink in that theory. The latest genetic analyses back up skeletal studies suggesting that some groups in the Amazon share a common ancestor with indigenous Australians and New Guineans. The find hints at the possibility that not one but two groups migrated across these continents to give rise to the first Americans.
“Our results suggest this working model that we had is not correct. There’s another early population that founded modern Native American populations,” says study coauthor David Reich, a geneticist at Harvard University.
The origin of the first Americans has been hotly debated for decades, and the questions of how many migratory groups crossed the land bridge, as well as how people dispersed after the crossing, continue to spark controversy. In 2008, a team studying DNA from 10,800-year-old poop concluded that a group of ancient humans in Oregon has ancestral ties to modern Native Americans. And in 2014, genetic analysis linked a 12,000-year-old skeleton found in an underwater cave in Mexico to modern Native Americans.
Genetic studies have since connected both these ancient and modern humans to ancestral populations in Eurasia, adding to the case that a single migratory surge produced the first human settlers in the Americas. —> read more: http://www.smithsonianmag.com/science-nature/