Human impact and climate changed killed megafauna
New evidence has revealed climate change played a key role in the extinction of ancient megafauna, with human impact “tipping them over the edge”.
JUST WHAT KILLED off the world's megafauna has long been a hotly debated topic – but new research confirms a rapidly warming climate was mostly to blame, with the arrival of humans acting as a 'final straw'.
In a new study published today in the journal Science Advances, researchers studying fossils in Patagonia, South America, found it was only after humans arrived, and when the climate started to warm, that the enormous ancient animals started to rapidly die off.
“Patagonia turns out to be the Rosetta Stone – it shows that human colonisation didn’t immediately result in extinctions, but only as long as it stayed cold,” said Professor Alan Cooper, Director of the Australian Centre for Ancient DNA at the University of Adelaide.
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Partial jaw of a large, extinct jaguar discovered in a cave in the Ultima Esperanza region of Patagonia. (Credit: Fabiana Martin/CEHA)
“Instead, more than 1000 years of human occupation passed before a rapid warming event occurred, and then the megafauna were extinct within a hundred years,” said Alan, who led the research.
Early human colonisation is nearly always implicated with megafauna extinctions, commented Dr Mark Warne, a geologist and palaeobiologist at Deakin University, who wasn't involved in the study.
“However, the research presented by Professor Cooper's team suggests that human expansion, in consort with climate change, was a potent combined force, that drove late Pleistocene megafauna extinction in Patagonia,” he said.
The researchers studied ancient DNA extracted from bones and teeth found in caves across parts of South America, in order to trace the genetic history of the populations.
Species such as the sabre-toothed cat, a sloth the size of an elephant and the enormous one-tonne short-faced bear (the world’s largest land-based mammalian carnivore) were once found widely across Patagonia, but seemed to disappear shortly after humans arrived.
“The Americas are unique in that humans moved through two continents, from Alaska to Patagonia, in just 1500 years,” said Professor Chris Turney, an expert in ancient climate change from the University of New South Wales and co-author on the paper.
“As they did so, they passed through distinctly different climate states – warm in the north, and cold in the south. As a result, we can contrast human impacts under the different climatic conditions.”
Similar impacts have been noted in Australia, according to Steve Webb, author of Corridors to Extinction and the Australian Megafauna.
“Accumulated climate changes throughout the Middle and late Pleistocene gradually wore down the number of species, the number of animals within species and isolated species,” said Steve, who wasn't involved with the new research.
“When humans eventually arrived they lived with the megafauna possibly for up to 10,000 years. But the vulnerability of these animals meant any predation by humans was disastrous because of their predicament and very low numbers,” said Steve.
“So, like South America, climate and eventually some human involvement tipped them over the edge.”