But they, or populations closely related to them, had mixed at some point with the East Asian-ancestry populations that were also part of the founding mixture.

This ancestral mixing happened in Asia — specifically in the region of Siberia and adjacent areas — before the peopling of the Americas began.

The resulting admixed population, carrying both East Asian and Ancient North Eurasian ancestry, eventually moved into Beringia and, at some point, across into North America.

This is what the paper meant by “dual ancestry” in its title.

Not dual ancestry within the Americas, but dual ancestry in the founding population that entered the Americas: one component from East Asian lineages, one component from ancient Siberian lineages related to MA-1.

Ancient North Eurasians In Plain Language