Ancient DNA is famously tough to extract and identify. Until today, the oldest sequenced DNA came from a horse that had lived up to 780,000 years ago. But new research breaks that record by a million years when remains found in north-eastern Siberia provided enough woolly mammoth DNA to sequence.
The paper, published today in Nature, describes the extraction of DNA from three mammoth specimens, dated 1.65 million, 1.34 million and 0.87 million years old respectively.
The researchers used a few pre-existing methods to extract DNA from the mammoth teeth. They then sequenced the genes and mapped them against genomes from African and Asian elephants.
Two of the mammoths appear to be from a lineage that precedes the woolly mammoth, while the oldest specimen comes from a previously unrecognised lineage. The researchers believe that this lineage was ancestral to mammoths that eventually colonised North America.
Aside from adding to our understanding of mammoth evolution, this paper shows that DNA can be extracted from much older samples than previously thought.
DNA often degrades quickly, so it’s difficult to analyse in old specimens. Researchers have had trouble obtaining a complete genome for the thylacine, which went extinct less than a century ago. But this paper indicates that in the right conditions, DNA can last for over a million years.
“Many present-day animal species arose during or after the Early Pleistocene,” an accompanying editorial notes. “The ability to retrieve DNA from Early Pleistocene specimens means that genomic changes in some lineages can now be tracked across deep time, providing insights into the evolution of modern species.”