Origin: A Genetic History of the Americas

East Asia, about 36,000 Years Ago
Around 36,000 years ago, a small group of people living in East Asia began
to break off from the larger ancestral East Asian population. We don’t know
why or how, but this group began to have fewer and fewer children with
their neighbors as time passed. Often this genetic signature signals a
population movement of some kind; geographic distance often results in
decreased gene flow between the two populations. We don’t yet have a
good idea of this process archaeologically, but we can see its signature in
the genomes of their descendants: a divergence of an East Asian group from
the larger population with some reduced gene flow continuing between
them for another 10,000 years or so.
By about 25,000 years ago, gene flow with the broader East Asian
population stopped completely. Again, we’re not sure what happened, but
another migration is a possibility. The smaller East Asian group itself split
into two. One, referred to by geneticists as the ancient Paleo-Siberians,
stayed in northeast Asia. The other became ancestral to the Indigenous
peoples of the Americas. Around 24,000 years ago, both groups
independently began interacting with an entirely different group of people:
the Ancient Northern Siberians (3).