Ancient South American populations dipped due to an erratic climate
Hunter-gatherers declined when weather patterns became unpredictable 8,600 years ago
By Bruce Bower
Ancient South American populations declined sharply as rainfall became increasingly unpredictable starting around 8,600 years ago, researchers say.
But hunter-gatherer groups from the Andes and the Amazon to the continent’s southern tip bounced back quickly once rain returned to a relatively stable pattern about 6,000 years ago, report archaeologists Philip Riris and Manuel Arroyo-Kalin, both of University College London.
During that roughly 2,600-year intervening period, bouts of unusually wet or dry conditions that disrupted local food sources occurred frequently, every five years or so on average, the scientists report online May 9 in Scientific Reports. Foragers would have been unable to predict whether extreme rainfall or drought was next up, or precisely when those conditions would hit. Previously, average rainfall patterns had included an abnormally wet or dry year only every 16 to 20 years, Riris and Arroyo-Kalin estimate from rainfall records gleaned from ancient sediments and other sources.