Mammoth teeth buried in Siberian permafrost for more than a million years have produced the oldest DNA sequenced ever, according to a study released Wednesday that showed a genetic reflector in the deep past.
The researchers said that the three specimens, one about 800,000 years old and two more than a million years old, provide important information about the giant mammals of the ice age, including the ancient heritage of the woolly mammoth.
Genomes go far beyond the oldest DNA sequenced previously – a horse dating back to 780,000 to 560,000 years ago.
“This DNA is incredibly old. The evidence is a thousand times older than the remains of the Vikings and even predates the existence of humans and Neanderthals, “said Love Dalen, a professor of evolutionary genetics at the Center for Paleogenetics in Stockholm and lead author of the journal Nature.
Mammoths were first discovered in the 1970s in Siberia and took place at the Russian Academy of Sciences in Moscow.
The researchers first dated the specimens geologically, compared to other species, such as small rodents, known to be unique for certain periods of time and found in the same sedimentary layers.
This suggested that two of the mammals were ancient steppe mammals over a million years old.
The youngest of the trio is one of the oldest wool mammoths found so far.
DNA jigsaw
The researchers also extracted genetic data from tiny samples of powder from each mammoth tooth, “essentially like a pinch of salt you would put on your dinner plate,” Dalen said in a press briefing. .
A wool mammoth necklace emerges from the permafrost on the central Wrangel Island in northeastern Siberia. Analysis of animal teeth yielded the oldest DNA sequenced ever [Love Dalén via AFP]
Although degraded into very small fragments, scientists have been able to sequence tens of millions of chemical base pairs, which make up DNA strands and make age estimates from genetic information.
This suggested that the oldest mammoth, named Krestovka, is even older at about 1.65 million years old, while the second, Adycha, is about 1.34 million years old, and the youngest Chukochya is 870,000 years.
Dalen said the discrepancy for the oldest mammoth could be an underestimation in the DNA dating process, meaning the creature was probably about 1.2 million years old, as geological evidence suggests.
But he said it was possible that the specimen was actually older and thawed from the permafrost at some point and then embedded 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 modern, high-quality DNA,” said science author Tom van der Valk of Science for Life. Laboratory, Uppsala University.
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’s genome.
The study found that the older Krestovka mammoth is a previously unrecognized genetic descendant, which researchers estimated to have moved away from other mammoths about two million years ago and was ancestral to those who colonized North America.
The study also traced descendants from a million-year-old Adycha steppe mammoth to Chukochya and other more recent wool mammoths.
He found genetic variants associated with life in the Arctic, such as hair, thermoregulation, fat deposits, and cold tolerance in the older specimen, suggesting that mammoths were already hairy long before the woolly mammoth appeared.
The giants of the ice age
Siberia alternated between the dry and cold ice conditions and the hot and humid periods.
Now, climate change is melting the permafrost and revealing more specimens, Dalen said, although increased rainfall could mean the remnants are washed away.
He said the new technologies mean it may be possible to sequence even older DNA from remains found in permafrost, which is 2.6 million years old.
Researchers are eager to look at creatures such as moose ancestors, mosses, wolves and lemmings to shed light on the evolution of modern species.
“Genomics was pushed deep into the ice age by giants,” said Alfred Roca, a professor in the Department of Animal Science at the University of Illinois, in an article published in Nature.
“The mammals that surrounded them may soon have their day.”