A study published on Wednesday showed that mammoth teeth buried in the permafrost of Siberia more than a million years ago yielded the oldest DNA sequence ever, shedding a genetic light on their deep past.
The researchers said the three specimens, one about 800,000 years old and two over a million years old, provide important insights into ice age giant mammals, including the ancient heritage of woolly mammoths.
Genomes far exceed the oldest previously sequenced DNA – a horse dating between 780,000 and 560,000 years ago.
“This DNA is incredibly ancient.” Love Dalen, professor of evolutionary genetics at the Center for Paleogenetics in Stockholm and lead author of the study published in the journal, said the samples are a thousand times older than the remains of the Vikings, and even predate the existence of humans and Neanderthals. .
Mammoths were originally discovered in Siberia in the 1970s and are held at the Russian Academy of Sciences in Moscow.
The researchers first dated the samples from a geological point of view, with comparisons to other species, such as small rodents, which are known to be unique for certain time periods and found in the same sedimentary layers.
This indicates that the two mammals were an ancient steppe mammoth over a million years old.
The smallest of the trio is one of the oldest woolly mammoths ever found.
The researchers also extracted genetic data from small samples of powder from each tooth of a mammoth, “basically like a pinch of salt you put on your dinner plate,” Dalin said at a press conference.
Although they have been degraded into very small pieces, scientists have been able to arrange tens of millions of chemical base pairs, which form strands of DNA, and make age estimates from the genetic information.
This indicates that the oldest mammoth, called Krestovka, is even larger at approximately 1.65 million years old, while the second mammoth, Adycha, is around 1.34 million years old and the youngest Chukochya is 870,000 years old.
The paradox for the oldest mammoth, Dalin said, may be the downplaying of the DNA dating process, which means the creature is likely to be around 1.2 million years old, as the geological evidence suggests.
But he said it was possible the sample was indeed older and melted from permafrost at some point and then got confined to a smaller layer of sediment.
Lead author Tom Van der Valk, of the Science for Life Lab at Uppsala University, said the DNA fragments were like a puzzle of millions of little pieces, “in a way, way, much smaller than what you can get from high-quality modern DNA”.
Using a genome from an African elephant, a modern relative of the mammoth, as a blueprint for their algorithm, the researchers were able to reconstruct parts of the mammoth genomes.
The study found that the older Krestovka mammoth represented a previously unrecognized genetic lineage that researchers estimate diverged from other mammoths about 2 million years ago and was the ancestor of those that colonized North America.
The study also traced the lineage from the million-year-old Adicha mammoth to Chukuchia and other modern woolly mammoths.
Genetic variants associated with arctic life, such as hair, thermoregulation, fat deposits and cold tolerance were found in ancient samples, indicating that the mammoth was indeed hairy long before the woolly mammoth appeared.
Ice Age giants
Siberia alternated between dry and cold ice age conditions and warm, humid periods.
Daleen said climate change is now melting permafrost and revealing more samples, although increased precipitation could mean washing away the remains.
He said the new technologies mean it may be possible to sequence even the oldest DNA from remnants found in permafrost, dating back 2.6 million years.
Researchers are keen to look at creatures such as the ancestors of moose, musk, wolves and lemons, to shed light on the evolution of modern species.
“Genomics has been pushed back into time by the giants of the Ice Age,” Alfred Rocca, a professor in the Department of Animal Science at the University of Illinois, said in an article published in Nature.
“The small mammals that surrounded them may have their day soon.”