Climate change, not human hunting, may have destroyed the thylacine (袋狼), according to a new study based on DNA from thylacine bones.
The meat-eating marsupials (有袋动物)died out in mainland Australia a few thousand years ago, but survived in Tasmania, an island of southeast Australia separated from the mainland, until the 1930s. Until now, scientists have believed the cause of this mainland extinction was increased activity from native Australians and dingoes (Australian wild dogs).
Scientists behind the study of the University of Adelaide, which was published in the Journal of Biogeography on Thursday, collected 51 new thylacine DNA samples from fossil (化石)bones and museum skins. The paper concluded that climate change starting about 4, 000 years ago was likely the main cause of the mainland extinction.
The ancient DNA showed that the mainland extinction of thylacines was rapid, and not the result of loss of genetic diversity (基因多样性). There was also evidence of a population crash (大跌)in thylacines in Tasmania at the same period of time, reducing their numbers and genetic diversity.
Professor Jeremy Austin said Tasmania would have been protected from mainland Australia's warmer, drier climate due to its higher rainfall. He argued that climate change was "the only thing that could have caused, or at least started the extinction on the mainland and caused a population crash in Tasmania".
"They both occurred at about the same time, and the other two things that have been talked about in the past and that may have driven thylacines to extinction on the mainland were dingoes and humans. So the only explanation that's left is climate change. And because that population crash happened when the species went extinct on the mainland, our argument is that there's a common theme there and the only common theme is that there is this change in climate."
