Scientists first managed to collect and analyze DNA from more than 1 million years ago, after extracting genetic material from mammoth remains found buried in Siberian permafrost.
Love Dalén of the Stockholm Center for Paleogenetics, who led the study published in the journal Nature, said the DNA taken from fossilized teeth was the oldest ever discovered, beating a previous record of 700,000 years from a horse bone found in the Canadian Arctic.
Adrian Lister, co-author of the Natural History Museum in London, said: “With millions of years old DNA we can expand [research] after the date of origin for many iconic species like mammoths.
“We can track how species evolve and how their adaptations came about.”
The research team extracted DNA from three ancient mammoth molars that had been stored in a Moscow freezer since their excavation in Siberia by Soviet paleontologists in the 1970s. Sophisticated genetic analysis would be far beyond the capabilities of the scientists of the time.
As climate change begins to melt the perpetual frost, mammoth tusks and bones are increasingly being discovered across Siberia, including Wrangel Island, where the last of the elephants lived about 4,000 years ago.
Even with today’s gene sequencing instruments, the project was a challenge. The small surviving DNA has broken down into a large number of tiny molecular parts.
Using a combination of geological and chemical techniques, the scientists concluded that the youngest tooth is 700,000 years old, and the next of 1 million and the oldest 1.2 million.
After reading the genetic codes, the researchers reconstructed the mammoth genome using computer programs that merged overlapping DNA sequences – guided by the known genomes of modern elephants and newer mammoths.
DNA analysis also revealed that the oldest tooth originated from a previously unknown species that researchers called Krestovka a mammoth after the place where it was found.
“This was a complete surprise,” said Tom van der Valk of the Center for Paleogenetics. “All previous studies have shown that at that time there was only one species of mammoth in Siberia, which was called the steppe mammoth.”
Two species of devoted mammoths later spawned woolly mammoths of the Canadian and Siberian Arctic and Colombian mammoths that roamed the more temperate regions of North America during the last ice age.
Genetic variants associated with Arctic life, such as hair growth, thermoregulation, fat deposits, and cold tolerance, were already present a million years ago, long before the formation of the woolly mammoth. These results show that most adaptations in the mammoth lineage occurred slowly and gradually over time.
Scientists believe similar research could be conducted on other species to shed light on a period of rapid climate and evolutionary change about 1m years ago.
“One of the big questions now is how far we can go backwards,” said Anders Götherström of the Center for Paleogenetics. “The educated assumption would be that we could recover 2 million years old DNA, and maybe go back as much as 2.6 million years. Before that, there was no eternal ice where ancient DNA could be preserved. “
So far, the oldest human DNA found comes from Spain and dates back about 400,000 years. Dalén said it might be possible to obtain an older sample from fossilized human remains stored in permafrost, “but nothing has been found so far.”