Illustration of a mammoth.
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MARY EVANS / SIPA
It is over a million years old.
The world's oldest DNA ever sequenced was recovered from mammoth teeth buried in permafrost in Siberia, a study published Wednesday in the journal
Nature said
.
The analyzes carried out on three specimens thus shed new light on the Ice Age and the legacy of the woolly mammoth, the last survivors of which only disappeared 4,000 years ago from the island of Wrangel, off the coast of Siberia.
The decrypted genomes here far exceed the oldest DNA ever sequenced so far, that of a horse 500,000 to 700,000 years old.
First less precise dates
The fossils analyzed were discovered in the 1970s in Siberia, in permafrost (deep frozen ground, also called permafrost), and kept at the Russian Academy of Sciences in Moscow.
The researchers first succeeded in dating the teeth (molars) by comparing them to other species, such as small rodents, known to have been unique to particular periods, and found in the same sedimentary layers.
These early comparisons suggested that two of the large mammals were ancient steppe mammoths over a million years old.
The "youngest" of the three, around 800,000 years old, was the oldest woolly mammoth (a species that diverged from the Steppe mammoth) ever discovered.
Sequencing of millions of base pairs
But the researchers went further, succeeding in extracting genetic data from tiny samples of dental powder, "like a pinch of salt to season a dish," Love Dalen, professor of genetics, told a press conference. from the Stockholm Center for Paleogenetics.
Despite their degraded condition, scientists have managed to sequence millions of base pairs, the building blocks that make up DNA, and estimate age from this valuable information, which is more accurate than geological evidence.
Verdict: The oldest mammoth, called Krestovka, is even older than initially estimated at 1.65 million years and the second, Adycha, is 1.34 million years old.
The youngest, Chukochya, is around 870,000 years old.
Other secrets revealed
Moreover, using the genome of an African elephant, a modern cousin of the mammoth, the researchers also discovered that the oldest, Krestovka, came from a heretofore unknown genetic line, which would have diverged from the others. species about 2 million years ago then colonized North America.
Other analyzes revealed genetic variations associated with life in the Arctic, such as hairiness, thermoregulation or fat deposits, suggesting that mammoths were hairy long before the appearance of their woolly congener.
The thaw of the Siberian permafrost, linked to global warming, brings to light more and more fossils.
A real gold mine that makes scientists eager to also study the past of smaller animals, such as the ancestors of elk, musk oxen, or lemmings.
If genetics have put the spotlight on the megafauna of the Ice Age, "the hour for small mammals may soon ring," said Alfred Roca, of the American University of Illinois, in a commentary published in study margin.
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