Origin: A Genetic History of the Americas

from later comparisons that the Mal’ta boys’ people were direct
descendants of the Ancient North Siberians from Yana (7). They were
broadly ancestral to present-day western Eurasians. But in comparing his
genome to those from populations across the world, they found that he was
also closely related to present-day Native Americans; his population was
directly ancestral to them. ii Mal’ta’s population—the Ancient Northern
Siberians—seems to have encountered the daughter East Asian population
described at the beginning of this chapter around 25,000 years ago and
interbred with them. Current estimates suggest that approximately 63
percent of the First Peoples’ ancestry comes from the East Asian group and
the rest from the Ancient North Siberians. We’re not sure where this
interaction took place. Some archaeologists believe that it occurred in East
Asia, suggesting that this is where the Siberians moved during the LGM.
There’s also a case to be made for this interaction having taken place
near the Lake Baikal region in Siberia from genetic evidence, too. The
ancient Paleo-Siberians, as mentioned earlier in this chapter, split from the
East Asian ancestors of Native Americans by about 25,000 years ago. They
are known to us from the genomes of an Upper Paleolithic person from the
Lake Baikal region known as UKY and a person from Northeastern Siberia
dating to about 9,800 years ago known as Kolyma1. Closely related to
Native Americans, these “cousin” genomes also show a mixture of ancestry
from Ancient North Siberian and East Asian populations, although the
proportion of East Asian ancestry is a bit higher than in Native Americans
—about 75 percent. The Ancient North Siberian gene flow into the East
Asian ancestors of the ancient Paleo-Siberians probably occurred at the
same time as into the ancestors of Native Americans—between about
25,000 and 20,000 years ago. Because UKY lived in the Lake Baikal region
some 14,000 years ago, some researchers argue, it seems likely that the
meeting between East Asians and Ancient North Siberians occurred in the
Trans-Baikal region (8).
But other archaeologists and geneticists argue that the meeting of the
two grandparent populations of Native Americans—the East Asians and the
Ancient Northern Siberians—occurred because people moved north, not
south, in response to the LGM. (In this scenario, Paleo-Siberian
descendants, like UKY, could have been the result of a southward
repopulation of Siberia out of Beringia.)