All this suggests that, around 14,000 years ago, the southern lineage of the first American Indians spread across the continent at a blinding speed. To imagine their movements, do not think of a tree that grows slowly, incrementally sending new branches and twigs. Instead, imagine a starburst, with many rays zooming simultaneously and quickly.
Over the centuries, these people had gone down on both sides of the Rockies, across the Great Basin, and toward the highlands of Mexico. Within a couple of millennia, they had closed the Andes, through the Amazon and up to the south as the continent allowed. "Once south of the ice, they found an open, vast and resourceful territory," says Moreno-Mayar, who is based at the University of Copenhagen. "They were adepts hunter-gatherers, so they expanded very quickly."
This pattern confirms the suspicions of archaeologists, whose findings had long suggested that humans suddenly appeared in all the Americas, from about 1
Coincidentally, a second group of researchers, flanked by Cosimo Posth from the Max Planck Institute for the Science of Human History, found the same model. They studied the DNA of 49 ancient humans from Central and South America and found similar evidence for rapid stellar expansion, and a southward migration linking the Clovis culture of the north to primitive peoples in Belize, Brazil and Chile.
Studies show that the stories of the Americas are more complicated than suggested by previous genetic studies, says Deborah Bolnick, an anthropologist at the University of Connecticut. But it's more because those studies were too simplistic to start with rather than because the new results are surprising. "Many lines of evidence, including archaeological research, linguistic data and indigenous stories, have suggested that more groups of related people, descended from shared but still distinct ancestors, have lived, moved and interacted in the Americas over the millennia. , " she says. "In general, this is what these studies show [new]."
They are not just reinventing the wheel, though. For example, the Clovis people's tools were so different from those found in the Cave of the Spirit (which is located on the other side of the Rocky Mountains) that some researchers took as proof that the Americas were populated by two genetically-founded founding groups. distinct. Moreno-Mayar and his colleagues denied this idea: they showed that the two groups were genetically similar, if culturally distinct.
Both teams also found evidence of subsequent migratory waves that took place long after the Americas were initially populated – although the details differ between the two studies. Posth's data point to a second wave of people entering South America some 9,000 years ago, whose genes have shifted those of former Clovis members, and which today had a direct link with indigenous groups. In contrast, Moreno-Mayar data speak of a more delicate process, in which relatively small groups have slowly spread both north and south from Mexico since 8000 years ago, adding their genes to the local populations without submerging them. In any case, "they question the idea that the native populations of our day all descend from a single, homogeneous ancestral population," says Maria Nieves-Colón, a geneticist of the Mexican Institute LANGEBIO .