THE first settlers colonised the Americas in more of a stutter than a sweep, according to archaeological evidence from Chile. Inhabited areas grew and shrunk to the beat of the fluctuating climate.
The oldest settlements date from about 15,000 years ago in what is now southern Chile and Patagonia. At the time, the Atacama desert in northern Chile was bone dry and absolutely unsuitable for humans, says Martin Grosjean of the University of Bern (Science, vol 298, p 821). As soon as the climate improved 2000 years later, people moved in. But they left about 9000 years ago, when it dried out again. Grosjean explains that the early settlers 鈥渕oved to the places where the animals were abundant鈥�.