The people who carried it had lived in Siberia during the Last Glacial Maximum.

They had contributed genetic material — through mixture and admixture in the complex population history of Pleistocene Asia — to the founding population that eventually crossed into the Americas.

This meant that the founding of the Americas was not a simple event in which a population directly derived from East Asia walked across a land bridge and populated a continent.

It was a more complex process that involved the mixing of at least two distinct genetic streams — East Asian ancestry and Ancient North Eurasian ancestry — somewhere in northeastern Asia, before or during the period when people were making their way toward the Americas.

The specific geography of where this mixing occurred, and over what time period, is still being worked out.