Million-year-old DNA sheds light on the genomic history of mammoths

Researchers Recover World’s Oldest DNA

A new international study led by the Centre for Palaeogenetics in Stockholm has discovered ancient DNA from a 1.2 million-year-old mammoth. It is so far the oldest DNA ever recovered. The project has revealed a new lineage in the mammoth family.  

Coming to the discovery, the genetic material was taken from the teeth of three mammoths found buried in the Siberian permafrost during the 1970s.

One of these specimens is around 700,000 years old and it represents one of the earliest known woolly mammoths. The other two are over a million-year-old and predate the existence of the woolly mammoth. 

Professor Love Dalén, study author from the Centre for Palaeogenetics in Stockholm, revealed at a press conference that this was the oldest DNA ever recovered. 

The second oldest of the specimens is from an ancient steppe mammoth (Mammuthus trogontherii), a direct ancestor of the woolly mammoth (Mammuthus primigenius), but the oldest specimen belongs to a previously unknown genetic lineage of mammoth, now referred to as the Krestovka mammoth. From the discovery, it now looks that the iconic Columbian mammoth (Mammuthus columbi) that inhabited North America during the last Ice Age was a hybrid between this Krestovka lineage and the woolly mammoth. 

Although the researchers estimate the oldest mammoth to be 1.2 million years old, the mitochondrial genome data shows the specimen could be up to 1.65 million years old and the second mammoth around 1.34 million years.

The previous oldest DNA was a horse found preserved in Canadian permafrost dating to 780,000-560,000 years ago. 

It is to be noted that the genomes of these mammals are becoming degraded over the millennia. An example is a recent discovery where the team found billions of tiny odd fragments of DNA rather than a nice long strip of genetic material. 

“The small piece you have, the harder it is to reconstruct the complete puzzle”, explained Dr Tom van Der Valk, lead study author from the Centre for Palaeogenetics in Stockholm. 

The team had few clues that helped them glue up the puzzle. They used high-quality genomes of woolly mammoths and present-day elephant relatives to use for reference. 

The result has built up confidence in the team, and they believe that it’s theoretically possible to recover DNA that’s even older than the mammoths.

The Northern Hemisphere doesn’t contain any permafrost that’s older than 2.5 million years, so recovering DNA beyond this time may prove extremely difficult, if not impossible.   

Professor Dalen also added that in the future we can see methods that can recover DNA from human non-permafrost specimens that are close to 1 million years old.

Journal Reference:
van der Valk, T., Pečnerová, P., Díez-del-Molino, D. et al. Million-year-old DNA sheds light on the genomic history of mammoths. Nature (2021). DOI: 10.1038/s41586-021-03224-9

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