2016-06-17. Rising temperatures and humans were a deadly combo for ancient South American megafauna.

posted Jun 18, 2016, 7:46 PM by Alan Gould
By Lizzie Wade, Science. For GSS Life and Climate chapter 12. Excerpt: If you’re fossil hunting in Patagonia you might find some weird creatures: giant jaguars, 3-meter-tall sloths, and bears 10 times the size of grizzlies. The southern part of South America was once crawling with these great beasts, collectively known as megafauna. But around 12,000 years ago, they suddenly disappeared from Patagonia and many other parts of the Americas. What caused the mass extinction? A new study suggests it was a one-two punch: rapid climate warming and humans. ...Alan Cooper, an evolutionary biologist at the University of Adelaide in Australia, radiocarbon dated nearly 100 fossils from Patagonia and sequenced their mitochondrial DNA, genes found in the power plants of cells and passed down only from the mother. When he lined up their ages with global climate records, he noticed a pattern: Many species of megafauna seemed to disappear during a period of extreme warming around 12,300 years ago, Cooper and his team write today in Science Advances. ...Patagonia warmed by about 2°C over 1000 years, and the effects were devastating: All but one of the species Cooper studied went extinct. ...Last year, Cooper spotted a similar pattern in North America, with megafauna going extinct during ancient warming events (which occurred at slightly different times in the Northern Hemisphere). The existence of complementary data from the two continents “is as close as you’re going to get to a replicated experiment,” he says....  http://www.sciencemag.org/news/2016/06/rising-temperatures-and-humans-were-deadly-combo-ancient-south-american-megafauna