Mammoth teeth buried in Siberian permafrost for more than a million years have yielded the oldest DNA ever sequenced, according to a study published Wednesday, which shines a genetic spotlight into the deep past.
Researchers said the three specimens, one about 800,000 years old and two more than a million years old, provide important insights into the giant Ice Age mammals, including the woolly mammoth’s ancient heritage.
The genomes by far outnumber the oldest previously sequenced DNA – a horse dating from 780,000 to 560,000 years ago.
“This DNA is incredibly old. The samples are a thousand times older than Viking remains and even predate the existence of humans and Neanderthals, ”said Love Dalen, professor of evolutionary genetics at the Center for Paleogenetics in Stockholm and the senior author of the study in the magazine is published, Nature.
The mammoths were originally discovered in Siberia in the 1970s and were held at the Russian Academy of Sciences in Moscow.
Researchers geologically dated the specimens first, comparing them to other species, such as small rodents, which are known to be unique to certain time periods and found in the same sedimentary layers.
This suggested that two of the mammals were ancient steppe mammoths over a million years old.
The youngest of the trio is one of the earliest woolly mammoths ever found.
DNA jigsaw puzzle
Researchers also extracted genetic data from tiny powdered powder from each mammoth tooth, “essentially like a pinch of salt you would put on your plate,” Dalen told a news conference.
A woolly mammoth tusk emerges from the permafrost on central Wrangel Island in northeastern Siberia. Analysis of the animals’ teeth has yielded the oldest DNA ever sequenced [Love Dalén via AFP]
Although it was broken down into very small fragments, scientists were able to sequence tens of millions of chemical base pairs that make up the strands of DNA and make age estimates based on the 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 old.
Dalen said the discrepancy for the oldest mammoth could be an underestimate in the DNA dating process, meaning the creature was likely about 1.2 million years old, as suggested by the geological evidence.
But he said it was possible that the specimen was indeed older and at some point had thawed out of the permafrost and then became trapped in a younger layer of sediment.
The DNA fragments were like a puzzle with millions of small pieces, “much, much, much smaller than you would get from modern, high-quality DNA,” said lead author Tom van der Valk of the 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, researchers were able to reconstruct parts of the mammoth genomes.
The study found that the older Krestovka mammoth represents a previously unrecognized genetic lineage, which researchers say diverged from other mammoths about two million years ago and was ancestral to those who colonized North America.
The study also traced the lineage of the million-year-old Adycha steppe mammoth to Chukochya and other more recent woolly mammoths.
It found gene variants associated with Arctic life, such as hairiness, thermoregulation, fat deposits, and cold tolerance in the older specimen, suggesting that mammoths were hairy long before the woolly mammoth emerged.
Ice Age Giants
Siberia has alternated between dry and cold ice ages and warm, wet periods.
With climate change melting the permafrost, revealing more specimens, Dalen said, although more rainfall could mean that remains are washed away.
He said new technologies make it possible to sequence even older DNA from remains found in the permafrost, which is 2.6 million years old.
Researchers like to look at creatures such as the ancestors of elk, musk oxen, wolves, and lemmings, to shed light on the evolution of modern species.
“Genomics has been pushed deep in time by the giants of the Ice Age,” said Alfred Roca, a professor in the animal sciences department at the University of Illinois, in a commentary published in Nature.
“The small mammals that surrounded them could soon have their day too.”