PARIS – A wide-ranging probe into woolly mammoths has added to evidence that they were wiped out by climate change.
British and Swedish researchers sequenced DNA from 88 samples of mammoth bone, tooth and tusk, looking for a signature in the genetic code that is handed down on the maternal line. They used this to build a family tree of mammoths spanning 200,000 years, across northern Eurasia and North America.
They found two periods of big population shake-up, both occurring in interglacials, or periods between ice ages.
A warm period 120,000 years ago caused populations to decline and become fragmented, leading to the emergence of a distinct type of mammoth that lived in Western Europe.
The cold then returned for a 100,000-year period called the Late Pleistocene — the last ice age. Superbly adapted to the cold, arid steppe and tundra, mammoths were the kings of the north.
Then, as the temperatures gradually rose once more, the populations shifted again and the mammoths were again confined to small pockets of favorable habitat.
What happened next is the final chapter in the great mammoth mystery.
Other researchers have concluded that climate change drove the mammoth to the brink but say it was hunting by humans that delivered the final blow. But humans could hardly be to blame if mammoths were able — as in previous interglacials — to hole up in some chilly redoubt that was too remote for habitation or hunting. “Spells of warm climate made the mammoth more susceptible to extinction,” said Love Dalen at the Swedish Museum of Natural History.
But to understand why the entire species became extinct, further investigations are needed in the final places where mammoths survived, said Dalen. Wrangel Island, in the Siberian Arctic, and the island of St. Paul, off Alaska, are believed to have been the mammoths’ last refuge. Populations there may have survived until 6,000 years ago.
The study appears in Proceedings of the Royal Society B.