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Three years later, Sandro L. Bonatto and Francisco M. Bolzano, two geneticists at the Federal University of Rio Grande do Sul, in the southern Brazilian city of Pôrto Alegre, analyzed Indian mitochondrial DNA again—and painted a different picture. Wallace and Neel had focused on the three haplogroups that are also common in Asia. Instead, the Brazilians looked at the fourth main haplogroup—Haplogroup A is its unimaginative name—which is almost completely absent from Siberia but found in every Native American population. Because of its rarity in Siberia, the multiple-migrations theory had the implicit and very awkward corollary that the tiny minority of people with Haplogroup A just happened to be among the small bands that crossed Beringia—not just once, but several times. The two men argued it was more probable that a single migration had left Asia, and that some people in Haplogroup A were in it.

By tallying the accumulated genetic differences in Haplogroup A members, Bonatto and Bolzano calculated that Indians had left Asia thirty-three thousand to forty-three thousand years ago, even earlier than estimated by Wallace and Neel. Not only that, the measurements by Bonatto and Bolzano suggested that soon after the migrants arrived in Beringia they split in two. One half set off for Canada and the United States. Meanwhile, the other half remained in Beringia, which was then comparatively hospitable. The paleo-Indians who went south would not have had a difficult journey, because they arrived a little bit before the peak of the last Ice Age—before, that is, the two glacial sheets in Canada merged together. When that ice barrier closed, though, the Indians who stayed in Beringia were stuck there for the duration: almost twenty thousand years. Finally the temperatures rose, and some of them went south, creating a second wave and then, possibly, a third. In other words, just one group of paleo-Indians colonized the Americas, but it did so two or three times.

As other measurements came in, the confusion only increased. Geneticists disagreed about whether the totality of the data implied one or more migrations; whether the ancestral population(s) were small (as some measure of mitochondrial DNA diversity suggested) or large (as others indicated); whether Indians had migrated from Mongolia, the region around Lake Baikal in southern Siberia, or coastal east Asia, even possibly Japan.

Everything seemed up for grabs—or, anyway, almost everything. In the welter of contradictory data, University of Hawaii geneticist Rebecca L. Cann reported in 2001, “only one thing is certain”: scientists may argue about everything else, she said, but they all believe that “the ‘Clovis First’ archaeological model of a late entry of migrants into North America is unsupported by the bulk of new archaeological and genetic evidence.”

COAST TO COAST

The “new archaeological evidence” to which Cann referred was from Monte Verde, a boggy Chilean riverbank excavated by Tom Dillehay of the University of Kentucky; Mario Pino of the University of Chile in Valdivia; and a team of students and specialists. They began work in 1977, finished excavation in 1985, and published their final reports in two massive volumes in 1989 and 1997. In the twenty years between the first shovelsful of dirt and the final errata sheets, the scientists concluded that paleo-Indians had occupied Monte Verde at least 12,800 years ago. Not only that, they turned up suggestive indications of human habitation more than 32,000 years ago. Monte Verde, in southern Chile, is ten thousand miles from the Bering Strait. Archaeologists have tended to believe that paleo-Indians would have needed millennia to walk from the north end of the Americas to the south. If Monte Verde was a minimum of 12,800 years old, Indians must have come to the Americas thousands of years before that. For the most part, archaeologists had lacked the expertise to address the anti-Clovis evidence from genetics and linguistics. But Monte Verde was archaeology. Dillehay had dug up something like a village,