The first Americans may have traveled across a land bridge and south from Alaska in two separate groups at about the same time
Diversity ruled among the first American settlers. Within a relatively short time span, at least two groups of people trekked across a land bridge from Asia to Alaska and then went their separate ways, one down the Pacific Coast and the other into the heart of North America, a new genetic study suggests.
A team led by geneticist Antonio Torroni of the University of Pavia in Italy estimates that these separate migrations into the New World occurred between 17,000 and 15,000 years ago.
Even more populations with distinct genetic signatures and languages may have crossed a now-submerged strip of land, known as Beringia, that connected northeastern Asia to North America within that relatively narrow window of time, the scientists also contend in a paper published online January 8 and in the Jan. 13 Current Biology.
“Whereas some recent investigators had thought that a single major population expansion explained all mitochondrial DNA variation amon