World's oldest DNA sequenced from million-year-old mammoths

Researchers said the three specimens, one roughly 800,000 years old and two over a million years old, provide important insights into the giant Ice Age mammals, including the ancient heritage of the woolly mammoth.    

The genomes far exceed the oldest previously sequenced DNA -- a horse dating between 780,000 to 560,000 years ago.

"This DNA is incredibly old. The samples 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 Centre for Palaeogenetics in Stockholm, senior author of the study published in Nature.

The mammoths were originally discovered in the 1970s in Siberia and held at the Russian Academy of Sciences in Moscow. 

Researchers first dated the specimens geologically, with comparisons to other species, like small rodents, known to be unique to particular time periods and found in the same sedimentary layers. 

This suggested that two of the mammals were ancient steppe mammoths more than a million years old.

The youngest of the trio is one of the earliest woolly mammoths yet found.

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 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 around 1.34 million years old, and the youngest Chukochya is 870,000 years old.

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. 

It found gene variants associated with life in the Arctic, like hairiness, thermoregulation, fat deposits and cold tolerance in the older specimen, suggesting mammoths were already hairy long before the woolly mammoth emerged.