Mammoths were driven to extinction by climate change, DNA research shows

Woolly mammoths roamed Earth for 5 million years until they vanished for good nearly 4,000 years ago – and scientists have finally proved why.

They say it’s down to climate change, because as icebergs melted, it became far too wet for the giant animals to survive as their food source – vegetation – was practically wiped out.

Previously many people believed that the sudden demise of the hairy cousins of current elephants must have been due to humans.

Watch: Which countries release the most CO2?

Mammoths lived alongside early humans: their skeletons were used to build shelters, harpoons were carved from their giant tusks, artwork featuring them is daubed on cave walls, and, 30,000 years ago, the oldest known musical instrument, a flute, was made out of a mammoth bone.

Read more: Why economists worry that reversing climate change is hopeless

Geneticists analysed ancient environmental DNA using shotgun sequencing to analyse environmental plant and animal remains – including urine, faeces and skin cells – taken from soil samples painstakingly collected over a period of 20 years from sites in the Arctic where mammoth remains were found.

Professor Eske Willerslev, a fellow of St John’s College, University of Cambridge, said: “Scientists have argued for 100 years about why mammoths went extinct.

"Humans have been blamed because the animals had survived for millions of years without climate change killing them off before, but when they lived alongside humans they didn’t last long and we were accused of hunting them to death.

“Precipitation caused the demise of the hairy beasts because their food source was practically wiped out.

“We have finally been able to prove was that it was not just the climate changing that was the problem, but the speed of it that was the final nail in the coffin – they were not able to adapt quickly enough when the landscape dramatically transformed and their food became scarce.

“As the climate warmed up, trees and wetland plants took over and replaced the mammoth’s grassland habitats. And we should remember that there were a lot of animals around that were easier to hunt than a giant woolly mammoth – they could grow to the height of a double decker bus!”

Read more: A 1988 warning about climate change was mostly right

The woolly mammoth and its ancestors lived on earth for 5 million years and the huge beasts evolved and weathered several Ice Ages.

Despite the cold, a lot of vegetation grew to keep the various species of animals alive – grass, flowers, plants, and small shrubs would all have been eaten by the vegetarian mammoths, who probably used their tusks to shovel snow aside and are likely to have used their trunks to uproot tough grasses.

As part of the project, the team also sequenced the DNA of 1,500 Arctic plants for the very first time to be able to draw these globally significant conclusions.

Read more: Melting snow in Himalayas drives growth of green sea slime visible from space

Dr Yucheng Wang, lead author and a research associate at the Department of Zoology, University of Cambridge, said: “The most recent Ice Age – called the Pleistocene – ended 12,000 years ago when the glaciers began to melt and the roaming range of the herds of mammoths decreased.

“It was thought that mammoths began to go extinct then but we also found they actually survived beyond the Ice Age all in different regions of the Arctic and into the Holocene – the time that we are currently living in – far longer than scientists realised.

“We zoomed into the intricate detail of the environmental DNA and mapped out the population spread of these mammals and show how it becomes smaller and smaller and their genetic diversity gets smaller and smaller too, which made it even harder for them to survive.

“The dramatic speed of the climate changing was the final nail in the coffin.

“When the climate got wetter and the ice began to melt it led to the formation of lakes, rivers, and marshes. The ecosystem changed and the biomass of the vegetation reduced and would not have been able to sustain the herds of mammoths.

"We have shown that climate change, specifically precipitation, directly drives the change in the vegetation – humans had no impact on them at all based on our models.”

Watch: Mont Blanc's glacial melt is a stark reminder of climate change