Record set with ancient DNA 2 million years old
DNA breaks down over time, so the older it gets, the smaller the pieces become, until there is nothing left to detect. And the shorter the fragments, the more difficult it is to assign them to a specific group of plants or animals.
“The huge damage pattern clearly showed that it was ancient DNA,” says Willerslev, who says he and his colleagues started working with the Greenland samples in 2006. “When there are 2 millions of years, there has been so much evolutionary time, that whatever [species] you find are not necessarily very similar to what you see today.
The Danish team say the DNA they found was preserved by freezing temperatures and because it was bound to clay and quartz, which also slows down the degradation process.
Exactly how far in time researchers will be able to see remains an open question. “We’re probably close to the limit, but who knows,” says Tyler Murchie, a postdoctoral fellow at McMaster University who is developing methods to study ancient DNA. He notes that the Dutch researchers managed to combine several techniques to “create a robust reconstruction of this ecosystem”.
Willerslev once predicted that it would be impossible to recover DNA from anything that lived over a million years ago. Now that he has broken the record, he hesitates to say where the limit is. “I wouldn’t be surprised if…we could go back twice as far,” he said. “But I wouldn’t guarantee it.”