Humans may have played only a glancing role in the extinction of Ice Age giants such as the woolly mammoth, woolly rhino and giant sloth, a new study has suggested.
Instead scientists have found rapid spells of global warming were chiefly to blame for killing off the megafauna that dominated during the last glacial period.
They blame short warm periods resulting from climate change may have drastically changed rainfall patterns and vegetation in the areas where these beasts lived.
Rapid warming of the world where woolly mammoths and other megafauna like woolly rhinos (both shown in the illustration above) is thought to have led to their extinction rather than human hunting or habitat destruction. Scientists found large scale extinctions during the last ice age were linked to rapid global warming
Hunting and habitat destruction by humans, which have often been blamed for causing the extinction of ice age giants, are likely to only delivered the final blow to the animals pushed to the brink by climate change.
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The scientists say the fate of the giant animals had already been sealed long before human’s started harming their numbers.
HOW MAMMOTHS BRAVED THE COLD
Genetic research on woolly mammoths has helped to reveal how the ice age giants adapted to survive in the cold expanses of northern Asia and Europe.
Scientists compared the genomes of two woolly mammoths with those of Asian elephants – their closest living relatives – in an attempt to understand the differences between them.
The research found that woolly mammoths and Asian elephants have nearly 1.4 million DNA letters difference between their genomes.
These difference alter more than 1,600 genes, bringing about changes in skin and hair development, fat storage, metabolism and temperature sensation.
One mammoth gene, known as TRPV3, was involved in sensitivity to the cold.
It is thought these adaptations allowed the mammoth to survive in the freezing temperatures during the last ice age, but it is possible they left them ill equipped to cope as the climate warmed.
Professor Alan Cooper, director of the Australian Centre for Ancient DNA at the University of Adelaide who led the study, said; ‘This abrupt warming had a profound impact on climate that caused marked shifts in global rainfall and vegetation patterns.
‘Even without the presence of humans we saw mass extinctions.
‘When you add the modern addition of human pressures and fragmenting of the environment to the rapid changes brought by global warming, it raises serious concerns about the future of our environment.’
The researchers, whose work is published in the journal Science, used ancient DNA extracted from the fossilised remains of extinct ice age creatures and compared it to climate data stretching back 56,000 years.
The team were able to reconstruct changes in the climate through the Late Pliestocene using ice cores obtained from Greenland.
The DNA helped provide information about extinction events by allowing the researchers to look for periods when populations of the animals became restricted or contracted, causing a loss in genetic diversity.
The scientists had expected to see extinction events would correlate to extreme cold periods, but in fact they found it was periods when the climate rapidly warmed that coincided with the extinctions.
The research helps to explain the sudden disappearance of mammoths and giant sloths around 11,000 years ago at the end of the last ice age.
Scienitsts used DNA extracted from fossilsied remains of ice age beasts, such as the mammoth vertebrae melting out of ice in Yukon Territory, Canada, shown above, to look for genetic signals of population collapses that signify extinction events. They then compared these to climate data held in ice cores from Greenland
Scientists have debated what killed off woolly mammoths (above) and other ice age giants for decades, with illness and human hunters being among the favourite theories. The new research suggests humans played a minor but decisive role in killing off populations already vulnerable and depleted by global warming
One animal, the North American short-faced bear, had already vanished before humans arrived in the New World about 13,000 years ago.
In Eurasia, the woolly mammoth and other big animals persisted for thousands of years after modern humans showed up in this region 44,000 years ago, and then disappeared during a series of warm spells.
Scientists have long debated whether the disappearance of the mammoth, woolly rhino, giant sloth, short-faced bear, and other large ice-age species was primarily due to environmental influences or human activity.
Despite the findings, Professor Chris Turney, a palaeoclimate researcher at the University of New South Wales, said: ‘It is important to recognise that man still played an important role in the disappearance of the major megafauna species.
‘The abrupt warming of the climate caused massive changes to the environment that set the extinction events in motion, but the rise of humans applied the coup de grace to a population that was already under stress.’
The researchers extracted ancient DNA from megafauna to build up a picture of extinction events over the past 51,000 years. Above Professor Alan Cooper extracts a sample from bison bone found in permafrost
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