Million-year-old mammoth teeth yield world’s oldest DNA

Scientists have sequenced the oldest DNA yet, smashing through a symbolic barrier in the study of ancient genomes and opening an unprecedented window into the evolution of North America’s extinct Ice Age giants—the Columbian and woolly mammoths.

The feat is unlikely to spark a mammalian Jurassic-Park style recreation; the study isn’t the first to sequence a mammoth’s genome, nor does it bring humankind any closer to resurrecting a mammoth. Instead, the study of DNA more than a million years old, published in Nature on Wednesday, sets a milestone for the rapidly growing study of ancient DNA, nearly doubling the record for the oldest genome ever sequenced.

The DNA comes from three mammoth molars found in Siberia in the early 1970s by Russian paleontologist Andrei Sher, a legend in the field for his mammoth research. Researchers estimate that the youngest of the three teeth is about 500,000 to 800,000 years old, while the older two are between one million and 1.2 million years old. The next-oldest DNA ever sequenced came from a nearly 700,000-year-old horse fossil found in Canada’s Yukon Territory.

While it had degraded into very small fragments, scientists were able to sequence tens of millions of chemical base pairs, which make up the strands of DNA and conduct age estimates from the genetic information.

This suggested that the oldest mammoth, named Krestovka, is even older at approximately 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 underestimation in the DNA dating process, meaning the creature was likely around 1.2 million years old, as suggested by the geological evidence.

But he said it was possible the specimen was indeed older and had thawed out of the permafrost at one point and then become wedged in a younger layer of sediment.

The DNA fragments were like a puzzle with millions of tiny pieces, “way, way, way 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 unrecognised genetic lineage, which researchers estimated diverged from other mammoths around two million years ago and was ancestral to those that colonised North America.

The study also traced the lineage from the million-year-old Adycha steppe mammoth to Chukochya and other more recent woolly mammoths.