The teeth of mammoths buried for more than a million years in the Siberian permafrost, according to a study published on Wednesday, yielded the oldest DNA ever consecutive, revealing a genetic spotlight in the deep past.
According to researchers, the three specimens, one about 800,000 years old and two more than a million years old, have important insights into the giant ice age mammals, including the ancient heritage of the woolly mammoth.
The genome transcends the oldest DNA previously in succession, a horse dating between 780,000 and 560,000 years ago.
‘This DNA is incredibly old. The specimens are a thousand times older than Viking remains and before even the existence of humans and Neanderthals, ”said Love Dalen, a professor of evolutionary genetics at the Center for Paleogenogenics in Stockholm and the senior author of the study in the magazine was published, said. Nature.
The mammoths were originally discovered in Siberia in the 1970s and kept at the Russian Academy of Sciences in Moscow.
Researchers first geologically dated the samples, with comparisons with other species, such as small rodents, which are known to be unique for specific periods and occur in the same sedimentary layers.
This suggests that two of the mammals were ancient steppe mammoths that were more than a million years old.
The youngest of the trio is one of the earliest woolly mammoths yet to be found.
DNA jigsaw
Researchers also extracted genetic data from small powder samples from each mammoth tooth, “essentially like a pinch of salt you would put on your dining table,” Dalen said.
A woolly mammoth tusk comes from the permafrost on Wrangel Island in northeastern Siberia. The analysis of the teeth of the animals yielded the oldest DNA that has ever been followed up. [Love Dalén via AFP]
While degrading into very small fragments, scientists have been able to sequence tens of millions of chemical base pairs, which form the parts DNA and perform age estimates from the genetic information.
This suggests that the oldest mammoth, named Krestovka, is even older at about 1.65 million years, while the second, Adycha, is about 1.34 million years old and the youngest Chukochya is 870,000 years old.
Dalen said the difference between the oldest mammoth may be an underestimation of the DNA dating process, meaning the creature is probably about 1.2 million years old, as geological evidence suggests.
But he said it was possible that the sample was indeed older and that at some point it had thawed out of the permafrost and then stuck in a younger layer of sediment.
The DNA fragments were like a jigsaw puzzle with millions of tiny pieces, ‘way, way, much smaller than you would get from high quality modern DNA’, said lead author Tom van der Valk, of the Science for Life Laboratory, Uppsala University said. .
Using a genome of an African elephant, a modern relative of the mammoth, as a blueprint for their algorithm, researchers were able to reconstruct parts of the mammoth genome.
The study found that the older Krestovka mammoth represents a previously unrecognizable genetic lineage, which researchers say diverged from other mammoths about two million years ago and was the ancestor of those who colonized North America.
The study also traced the origin of the million-year-old Adycha steppe mammoth to Chukochya and other more recent woolly mammoths.
No variants related to life in the Arctic were found, such as hairiness, thermoregulation, fat deposits and cold tolerance in the older sample, suggesting that mammoths were hairy long before the woolly mammoth emerged.
Ice Age Giants
Siberia alternated between dry and cold ice age conditions and hot, wet periods.
Now climate change is melting the permafrost and revealing more samples, Dalen said, though increased rainfall could mean residues are washed away.
He said that new technologies mean that it is possible to sort even older DNA from remnants found in the permafrost, which is 2.6 million years old.
Researchers are eager to look at creatures like the ancestors of elk, musk oxen, wolves and lemmings, to make the evolution of modern species shine.
“Genomics was driven deep in time by the giants of the ice age,” Alfred Roca, a professor in the Department of Animal Science at the University of Illinois, said in a commentary published in Nature.
“The little mammals that surround them may soon have their day too.”