A new report published online in Current Biology has some explanations to a famous case: the disappearance of the last woolly mammoths. The massive 9-foot-tall creatures with their 20-inch-long hair and gigantic curved tusks long have been an icon for the frozen tundra of the last ice age.

Studying some ancient-DAN Dr. Ian Barnes, of Royal Holloway, University of London discovered revealed a “genetic signature” of a range expansion after the last interglacial period. After the mammoths’ migration, the population apparently leveled off, and one of two lineages died out.

“In combination with the results on other species, a picture is emerging of extinction not as a sudden event at the end of the last ice age, but as a piecemeal process over tens of thousands of years involving progressive loss of genetic diversity,” said Dr. Ian Barnes, of Royal Holloway, University of London. “For the mammoth, this seems much more likely to have been driven by environmental rather than human causes, even if humans might have been responsible for killing off the small, terminal populations that were left.”

The researchers analyzed 96 mammoth samples that often came as a result of gold mining in Alaska or paleontological digs in Siberia or Europe. The team's analyses suggest woolly mammoth populations remained mostly constant in size for their last 70,000 years.

Until now it was believed that ancient human tribes hunted the mammoths and other ice age giants to oblivion.

Barnes, along with Dr. Adrian Lister of the University College London and the Natural History Museum in London and others, had earlier found evidence that bison, bears, and lions underwent major population shifts twenty-five to fifty thousand years ago.