University of Utah scientists deciphered maternal genetic material from two babies buried together at an Alaskan campsite 11,500 years ago. They found the infants had different mothers, and were the northernmost known kin to two lineages of Native Americans found throughout North and South America.
     By showing that both genetic lineages lived so far north so long ago, the study supports the "Beringian standstill model," which says that Native Americans descended from people who migrated from Asia to Beringia - the land bridge that once linked Siberia and Alaska - and spent up to 10,000 years there before moving rapidly into the Americas beginning at least 15,000 years ago.
     University of Utah anthropology professor Dennis O'Rourke, the study's senior author, says: "These infants are the earliest human remains in northern North America, and they carry distinctly Native American lineages. We see diversity that is not present in modern Native American populations of the north and we see it at a fairly early date. This is evidence there was substantial genetic variation in the Beringian population before any of them moved south. You don't see any of these lineages that are distinctly Native American in Asia, even Siberia, so there had to be a period of isolation for these distinctive Native American lineages to have evolved away from their Asian ancestors."
     The burial of ancient infants is rare. They are among human remains at only eight known sites in North America older than 8,000 years, and from which researchers obtained mitochondrial DNA. The infants are the northernmost of all those remains, and of the two lineages they represent.
     "It's not common to find infants buried together that are not related maternally," O'Rourke adds. "It raises questions about the social structure and mortuary practices of these early people."
     O'Rourke suspects that both 11,500-year-old infants were at or near the root of their respective genealogical trees.
     Modern tribal populations in northern North America show little mitochondrial DNA diversity, O'Rourke says. "In small populations, some lineages just get lost and don't get passed on, and in others they become established and more common."

Edited from Phys.org (26 October 2015)