This is the first time that DNA has been left over from animals that are more than a million years old. Previously, it was the oldest DNA sample of a horse that lived between 560,000 and 780,000 years ago.
The information found from this giant of the ice age reveals how mammoths evolved and adapted to life in a cold climate. It can also display a previously unknown type of mammoth.
“This DNA is incredibly old. The specimens are a thousand times older than Viking remains and even pre-date the existence of humans and Neanderthals,” said Love Dalen, a professor of evolutionary genetics at the Center for Paleogenogenics in Stockholm. said.
An international team of researchers was able to isolate DNA from molars of three separate mammoths collected in the Siberian permafrost in the 1970s. They aged the teeth using geological data and by analyzing the DNA.
The oldest mammoth tooth is between 1.2 million and 1.65 million years ago. The younger estimate comes from a method known as biostratigraphy, where scientists assess the presence of small rodents in the sediment layers – species that only existed during certain periods.
The older estimate comes from the genome that the researchers restored.
“There could be different reasons why these estimates differ. Maybe the Krestovka sample originally came from an older layer, but at some point it was erased and then put back in a younger layer,” Dalen said.
“Alternatively, and in our opinion more likely, our estimated molecular clock speed is a bit off,” he said, suggesting that setting the date is not an exact science.
“Either way, both of these dating analyzes show an age of more than 1 million years.”
“Complete surprise”
The research, called the Krestovka mammoth, into the place where it was found, showed that this particular type of mammoth differs from other Siberian mammoths more than 2 million years ago.
“It was a total surprise to us. All previous studies indicated that at that time there was only one species of mammoth in Siberia, called the steppe mammoth,” said study co-author Tom van der Valk, a postdoctoral fellow. researcher, said. at the Swedish Museum of Natural History.
He said their DNA analysis shows that there are two different genetic lineages and that they can suggest different species. They also believe that it was mammoths that belonged to this previously unknown generation, which colonized North America about 1.5 million years ago.
Their analysis showed that traits related to life in the Arctic – hair growth, fat deposits and cold tolerance – were present more than a million years ago and that they would develop slowly and gradually over time. The latest specimen they found and sequenced was from a tooth of an early form of woolly mammoth that lived more than 680,000 years ago.
Even older DNA
While the permafrost helped preserve the DNA, it was still very challenging to extract from the samples, the researchers said. The DNA degraded into very small fragments that the researchers compared to a puzzle with more than a billion pieces. To inform the process, they used a detailed genome of a living African elephant, which bore a bit like the lid of a puzzle.
“It usually helps to have a lid of a box to sneak in the highlight, and so we use the elephant’s reference genome,” Dalen said.
If we can extract and analyze DNA that is millions of years old, it could enable scientists to trace the origin and evolution of many different species, including our own. In theory, the researchers said it was possible to extract DNA from 2.6 million-year-old samples.
This is the age of the earliest permafrost – soil that stays frozen all year round and helps to degrade the DNA. It is unlikely that ancient DNA could be preserved so well outside permafrost areas, they said.
In recent decades, this “thawing season” has become longer due to climate change, Dalen said. The region warmed up twice as fast as other parts of the planet. This led to an increase in the number of ancient finds.