Washington: Woolly mammoths and prehistoric horses grazed on the North American plains several thousand years longer than hitherto presumed.
This is shown by samples of ancient DNA, analysed by an international team of research scientists under the leadership of Eske Willerslev, professor at Copenhagen University.
Analyses of ancient DNA once again upsets results of more common methods of dating, such as carbon 14 analysis of bone and tooth remains from extinct animals.
These methods had previously dated the extinction of mammoths and prehistoric horses in Central Asia to 13-15,000 years ago.
But with the DNA-test methods of Eske Willerslev and his colleagues, this boundary has now moved between 2,600 and 5,600 years closer to our time and has thus revised our previous opinion of when the last mammoths and prehistoric horses grazed on the North American plains.
The ancient DNA that formed the basis of this sensational result was discovered by scientists in samples of soil from the permafrost tundra surrounding the windswept town of Stevens Village on the bank of the Yukon River in Central Alaska.
"With ancient DNA analysis, we are completely independent of skeletons, bones, teeth and other macro-fossil evidence from extinct animals," said Willerslev.
"Whilst an animal leaves only a single corpse when it dies, it leaves quantities of DNA traces through urine and faeces whilst it is still alive. It is these DNA traces which we find in the soil," added Willerslev.
Surprisingly, scientists found that the later samples with mammoth DNA could be dated back to between 10,500 and 7,500 years ago, and are therefore between 2,600 and 5,600 years after the supposed extinction of the mammoths from mainland Alaska.
Thus, the scientists found proof that mammoths had walked the earth several thousand years longer than previously believed, says a Copenhagen University release.
The report was published in the Proceedings of the National Academy of Sciences.