lunes, 20 de febrero de 2017

The Surprisingly Early Settlement of the Tibetan Plateau


Credit: Getty Images
 
Scientists thought people first set foot on the frozen Tibetan Plateau 15,000 years ago. New genomic analyses suggest multiplying that figure as much as fourfold

The first humans who ventured onto the Tibetan Plateau, often called the “roof of the world,” faced one of the most brutal environments our species has ever confronted. At an average elevation of more than 4,500 meters, it is a cold and arid place with half the oxygen present at sea level. Although scientists had long thought no one set foot on the plateau until 15,000 years ago, new genetic and archaeological data indicate that this event may have taken place much earlier—possibly as far back as 62,000 years ago, in the middle of the last ice age. A better understanding of the history of migration and population growth in the region could help unravel the mysteries of Tibetans' origin and offer clues as to how humans have adapted to low-oxygen conditions at high altitudes.

As reported in a recent study in the American Journal of Human Genetics, researchers got a better grasp of the plateau's settlement history by sequencing the entire genomes of 38 ethnic Tibetans and comparing the results with the genomic sequences of other ethnic groups. “It has revealed a complex patchwork of prehistoric migration,” says Shuhua Xu, a population geneticist at the Chinese Academy of Sciences' Shanghai Institutes for Biological Sciences. “A big surprise was the antiquity of Tibetan-specific DNA sequences,” Xu says. “They can be traced back to ancestors 62,000 to 38,000 years ago, possibly representing the earliest colonization of the plateau.” [...] Scientific American