Woolly mammoths roamed the Earth for five million years, almost completely disappearing almost 4,000 years ago. These furry cousins of elephants coexisted with primitive humans and were a regular fixture in their diet for a long time. In addition, their skeletons were used to build shelters, harpoons were carved from their giant tusks, and even the oldest known musical instrument, a 30,000-year-old flute, was carved from mammoth bone. However, it seems that this intense human exploitation would not have been the cause of the extinction of the mammoths, as revealed by a genetic analysis work that has just been published in the journal Nature .
According to their authors, when the icebergs melted, the climate became too humid and vegetation, their main source of food, was practically eliminated. To reach these conclusions, the researchers used DNA sequencing to analyze environmental remains of plants and animals, including urine, feces and skin cells, taken from soil samples carefully collected over a period of twenty years at sites in the Arctic where mammoth remains were found. New advanced technology means that scientists no longer have to rely on DNA samples from bones or teeth to collect enough genetic material to recreate an ancient DNA profile. This same technique has been used, for example, during the pandemic to analyze wastewater from human populations to detect, track and analyze Covid-19.
“We were finally able to show that the problem was not just climate change, but that its speed was the last straw: mammoths were unable to adapt fast enough when the landscape changed dramatically and their food was scarce,” says Eske. Willerslev, Fellow of St John’s College, University of Cambridge and Director of the Center for Geogenetics at the Lundbeck Foundation at the University of Copenhagen. “ As the climate warmed, wetland trees and plants replaced mammoth grassland habitats. And we must remember that there were many animals around that were easier to hunt than a giant woolly mammoth, they could grow to the height of a double-decker bus! “
Life in the cold
The woolly mammoth and its ancestors lived on earth for five million years, evolved, and withstood several ice ages. During this period, herds of mammoths, reindeer, and woolly rhinos thrived in the cold, snowy conditions.
Despite the cold, a large amount of vegetation grew that kept the various species of animals alive: the vegetarian mammoths would have eaten grass, flowers, plants and small bushes. These giants would use their huge fangs to push snow away for food, and they were so big because they needed huge stomachs to digest the grass.
Mammoths could travel a distance equivalent to going around the world twice during their lifetime, and fossil records show that they lived on every continent except Australia and South America. The populations were known to have initially survived to the end of the last Ice Age in small pockets off the coasts of Siberia and Alaska, on Wrangel Island and St Paul Island, but research found that they actually lived longer in others. places and that the breeds of mammoths on both islands were closely related despite being geographically separate. As part of the project, the team also sequenced the DNA of 1,500 Arctic plants for the first time in order to draw these conclusions.
Dr Yucheng Wang, first author of the paper and associate researcher in the Department of Zoology at the University of Cambridge, said: “ The most recent Ice Age, called the Pleistocene, ended 12,000 years ago when glaciers began to melt and the Roaming range of mammoth herds decreased. Mammoths were thought to have started going extinct then, but we also found that they actually survived beyond the Ice Age in different regions of the Arctic and into the Holocene, the time we currently live in, much longer than previously thought. .
“We zoomed in on the intricate details of environmental DNA and mapped the population distribution of these mammals and showed how it gets smaller and smaller and their genetic diversity gets smaller and smaller, making it even more difficult for them. survive “.
“When the climate became more humid and the ice began to melt, it resulted in the formation of lakes, rivers and salt marshes. The ecosystem changed and the biomass of the vegetation was reduced, so it could not feed the herds. We have shown that climate change, specifically precipitation, directly drives change in vegetation; humans had no impact on them according to our models ”, says the researcher.
“This study shows that nothing is guaranteed when it comes to the impact of dramatic changes in the climate. The first humans would have seen the world change beyond recognition – that could easily happen again and we cannot take it for granted that we will even be there to witness it. The only thing we can predict with certainty is that the change will be massive, ”recalls Willerslev.
Text: Cambridge University
