Million-Year-Old DNA Samples Pulled From Mammoth Teeth

AILSA CHANG, HOST:

You would think after being extinct for thousands of years, mammoths would have no more surprises. Well, the world's oldest DNA samples say otherwise. Two mammoth molars pulled from the permafrost in northeastern Siberia contain DNA dating back to more than a million years ago.

LOVE DALEN: It's a big leap backwards in time. That's for sure.

CHANG: Love Dalen is at the Center for Paleogenetics in Stockholm, and he says this mammoth DNA is twice as old as the previous record holder, which came from an ancient horse.

CHANG: Now, sequencing million-year-old DNA like this was impossible just a few years ago. Samples that old were just too small to work with. Now researchers can see incredibly small samples, but it's challenging to put them together. Tom van der Valk also works with the Center for Paleogenetics.

TOM VAN DER VALK: Imagine if your DNA is fragmented into literally millions of tiny pieces.

ARI SHAPIRO, HOST:

It is a painstaking puzzle.

DALEN: And it's not only one puzzle. It's actually multiple puzzles. So imagine, you know, you have one puzzle for the mammoth genome, but then you have another puzzle for the whole bacterial content of these samples, and you have another puzzle for the human DNA for the paleontologists and us in the lab.

SHAPIRO: Well, once they had finished sorting out the mammoth bits, the DNA gave the scientists a unique window into mammoth evolution. Dalen says the standard view holds there was only one mammoth species in Siberia a couple million years ago.

DALEN: What we find now is that actually we found two different lineages. We can't really say they are different species, but there are clearly two different genetic types of mammoths, so that came as a complete surprise to us.

CHANG: The ancient DNA also gives clues to the origins of the Columbian mammoth, which lived in North and Central America. Here's Tom van der Valk again.

VAN DER VALK: Could kind of show that this Columbian mammoth is a hybrid species between two of the genetic lineages. So one is the new genetic lineage that we found in this paper, and the other is the woolly mammoth genetic lineage, so to say.

CHANG: Their work appears today in the journal Nature.

SHAPIRO: Alfred Roca of the University of Illinois at Urbana-Champaign wasn't involved in the work but wrote an accompanying editorial.

ALFRED ROCA: It's an absolutely amazing discovery. It takes back the field of ancient DNA twice as far in geological time as before.

CHANG: And that genetic puzzling unlocks the possibility, he says, that we may soon find more evolutionary play-by-plays hiding in super-old DNA.

(SOUNDBITE OF LOS CAMPESINOS SONG, "YOU! ME! DANCING!") Transcript provided by NPR, Copyright NPR.