World’s oldest DNA is 2 million years old

DNA from 2 million years ago, the oldest ever extracted, has been obtained from ice age sediments in Greenland, a discovery that opens a new chapter for paleogenetics, scientists announced on Wednesday (7).

“DNA was able to survive for 2 million years, twice as long as the oldest DNA found previously,” Mikkel Winther Pedersen, one of the lead authors of the study, told AFP in the journal Nature.

Identified in sediments, the different DNA fragments come “from the northernmost part of Greenland, called Kap Kobenhavn, and belong to an environment that we don’t see on Earth today,” he said.

They were very well preserved, as they were frozen and were found on little explored surfaces, continued the professor from the University of Copenhagen.

“The rivers carried minerals and organic matter to the marine environment, where these terrestrial sediments were deposited. Then, about 2 million years ago, this underwater land mass reemerged and became part of northern Greenland”, he explained.

Kap Kobenhavn is today an arctic desert, where several types of deposits have already been discovered, including very well preserved fossils of plants and insects.

The researchers did not try to determine the DNA origin of the elements found and there was very little information about the possible presence of animals. But the work, which started in 2006, allowed the outline of the region to be traced back to 2 million years ago.

“We had a forest environment with mastodons, reindeer, hares and a large number of plant species. We found 102 taxa (grouping of related organisms) of different plants”, said Pedersen.

According to him, the presence of the mastodon is particularly notable, as it had never been observed so far north.

The researchers reflected on the adaptability of the species because, 2 million years ago, Greenland, green land in Danish, had maximum temperatures of 11º to 17ºC, but, in these latitudes, the sun does not set during the summer months nor does it rise during the winter.

“We don’t see this association of species anywhere else on Earth today”, highlighted the expert in paleoecology.

This “suggests that the plasticity of species — the way they are able to adapt to different types of climate — may be different from what we thought before,” he explained.

Thanks to innovative technology, the researchers discovered that the 41 fragments studied are 1 million years older than the last DNA record obtained from a Siberian mammoth bone.

It was necessary to determine whether the DNA was hidden in clay and quartz. Afterwards, it was possible to separate it from the sediment to examine it.

The method used provides a fundamental understanding of why minerals or sediments can preserve DNA. “It’s a Pandora’s box that we’re about to open,” explained Karina Sand, who leads the geobiology group at the University of Copenhagen and participated in the study.

For Pedersen, with this discovery “we broke the barrier of what we thought we could achieve in terms of genetic studies”.

“For a long time we believed that 1 million years was the limit of survival of DNA, but today we see that it is twice as long. And, of course, this pushes us to look for other places”, he added. “There are several places in the world that have geological deposits as old as or older”, says the researcher.