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Which Way Did They Go?

An examination of ancient bison and other DNA is informing researchers' idea of how people migrated to the Americas, as bison were a main prey of humans, the New York Times reports. But, it adds, the two groups that have taken this approach have come to differing conclusions.

Beth Shapiro and her team at the University of California, Santa Cruz, and elsewhere turned to a combination of radiocarbon dating and mitochondrial DNA analysis of late Pleistocene bison fossils to gauge when the Ice Free Corridor between Alaska and the rest of North America was open. With this approach, they dated that opening to about 13,000 years ago — just before the appearance of Clovis technology in interior North America — as they reported recently in the Proceedings of the National Academy of Sciences.

However, Eske Willerslev from the University of Copenhagen and his colleagues report in Nature this week that they analyzed ancient DNA from bison, rabbits, and as well as pollen isolated from the region to time that opening to 12,500 years ago. That, they say, makes it less likely that the forebears of the Clovis people could've traversed that corridor.

The Times notes that each group finds flaws in the other's approach. Willerslev says the bison Shapiro's team studied could've diverged before the glacier cut them and the corridor off, while the University of Alberta's John Ives, one of Shapiro's co-authors, says the samples Willerslev's team studied might not actually be from the site of the lake formed by the melting glaciers.