At this point, humans have earned their reputation as harbingers of extinction. It was long thought that humans played a major role in killing off mammoths and the other massive animals — or megafauna — of the Pleistocene epoch, but it turns out that humans are mostly off the hook for this one.

Rapid warming of the global climate, not the arrival of humans, was the chief driver of megafaunal extinctions during the Pleistocene, according to a paper published in the journal Science.

"Other studies that have been done have suggested that humans were largely responsible for the megafaunal extinctions, particularly because of the close match between the timing at which humans first moved into a new area and the timing of the extinctions of the megafauna in that area," lead study author Alan Cooper of the University of Adelaide told Tech Times. "Our findings are swinging the debate back towards climate as having a much more instrumental role in these events."

Most of the previous work on this subject had been done with fossil records, looking at the time at which species appear to go extinct.

"The problem with that approach has been that if fossils of the species are present throughout time, the assumption has been that everything was OK — that there weren't any major changes going on," Cooper said.

By analyzing ancient DNA from museum specimens, the researchers were able to gain a much finer picture of the changes that occurred in megafauna populations many thousands of years ago.

"With the DNA that we extracted from the bones, we've been able to see a very dynamic process of localized and larger extinctions going on all the way through time that have been invisible to the fossil record," said Cooper.

The researchers also constructed a new, higher resolution timeline of climate change using data gathered from Greenland glacial ice cores and sedimentary rocks in Venezuela. The improved resolution of both population and climate data were key to their findings. 

"When we compared them, that's when the we could see this close correlation between the warming events and and the extinctions," Cooper said.

Humans seem to have essentially finished off the surviving members of populations already severely weakened by the rapidly warming global climate, according to the study. While humans were not the cause of the global warming that occurred in that case, Cooper said that these findings demonstrate why we should be taking the threat of global climate change seriously now.

"I had to learn a lot about climate change for this paper and it's just been absolutely eye-opening to learn about how powerful these global climate systems are," he said.

Photo: Rob Pongsajapan | Flickr

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