Scientists Decode The DNA Of A Woolly Mammoth
Using DNA encased in hair shafts, researchers have determined the DNA sequence of a woolly mammoth. It's the first extinct mammal to have its sequence deciphered.
"Mammoths and elephants are, on the sequence level, very similar," says Stephan Schuster of Pennsylvania State University who led the sequencing team. "[There is a] 99.4 percent equivalence between the two."
Schuster's team used a variety of mammoth remains to conduct its study. Each was frozen in the Siberian permafrost, some for tens of thousands of years. The DNA came from the dead animal's hair.
"Unlike what you hear on CSI, you don't need to have a hair follicle to find DNA attached with hair," Schuster says. "We isolate DNA from the hair shaft."
A problem with analyzing DNA from ancient samples is that there's typically a lot of DNA from bacteria and viruses contaminating the sample that you have to get rid of.
"The way that we get rid of it is we shampoo and bleach the hair," Schuster says.
Not only does this make the hair soft and manageable, but what's left inside the hair shafts is almost exclusively mammoth DNA.
Schuster says the DNA is not the long strands found in living cells. It is millions of tiny fragments. But new sequencing machines can read those fragments, and new computer programs can stitch them together to form a complete sequence — or at least a nearly complete sequence.
It's tempting to speculate that with the DNA sequence in hand it might be possible to recreate an extinct mammoth using a mixture of genetic engineering and cloning. Molecular geneticist Tom Gilbert of the University of Copenhagen is skeptical, at least in the short term.
"I should warn upfront that I have a history of saying it's not possible, and then within months some technological breakthrough comes that makes me revise my opinion," says Gilbert.
He says the real value of having the sequence data is that it will help scientists understand how elephants evolved.
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ROBERT SIEGEL, host:
From NPR News, it's All Things Considered. I'm Robert Siegel.
MELISSA BLOCK, host:
And I'm Melissa Block. Our next story is huge. You could even say that it's mammoth. Scientists at Penn State University are reporting that they've figured out the letters that make up the genome of a woolly mammoth. It's the first extinct species to get its genome sequenced. The information will help explain how mammoths differed from modern elephants, and it may even say something about human evolution. Here's NPR's Joe Palca.
JOE PALCA: Let's say you study ancient DNA and you're lucky enough to stumble across a woolly mammoth's remains in the Siberian permafrost. The mammoth's been dead for thousands of years. A reasonable first question is, where the heck do you get some DNA from? Well, it turns out one very good place to get DNA from is hair.
Dr. STEPHAN SCHUSTER (Biochemistry and Molecular Biology Associate Professor, Pennsylvania State University): Unlike what you hear on CSI, you don't need to have a hair follicle to find DNA attached with hair. We isolate the DNA from the hair shaft.
PALCA: Stephan Schuster is at the Pennsylvania State University.
Dr. SCHUSTER: The problem with mammoth, as it is with all ancient DNA, is there's always a large amount of DNA that is contaminating. The DNA that is coming from the organism that you wanted to study.
PALCA: Even in the Siberian permafrost, where the extinct mammoths Schuster's study came from, ancient samples are covered with DNA from bacteria and viruses and the like that may once have lived in or on mammoth remains. But Schuster says there's a way to deal with contaminating DNA in hair.
Dr. SCHUSTER: The way that we get rid of it is that we shampoo and bleach the hair on the outside.
PALCA: Not only does this make the hair soft and manageable, but what's left inside the hair shafts is almost exclusively mammoth DNA. Schuster says the DNA is not the long strands found in living cells, instead it's millions of tiny fragments. But new sequencing machines can read these fragments and new computer programs can stitch together the fragments to form a complete sequence, or at least a nearly complete sequence. Tom Gilbert also studies ancient DNA. He's at the University of Copenhagen. He says reaching this sequencing milestone was expected.
Dr. TOM GILBERT (Molecular Geneticist, University of Copenhagen): I'm not surprised, no, because I've seen the developments that have been happening all along. That's not to say it's not a fantastic achievement.
PALCA: Now, it's tempting to speculate that with the DNA sequence in hand, it might be possible to recreate an extinct mammoth using a mixture of genetic engineering and cloning. Maybe, but Gilbert is skeptical, at least in a short term.
Dr. GILBERT: I should warn upfront that I have a history of saying it's not possible, and then within months some technological breakthrough comes through that makes me revise my opinion.
PALCA: Gilbert says the real value of having the sequence data is that it will help scientists understand how elephants evolved.
Dr. GILBERT: Elephants, they live in warm climates. They live in Asia, Africa. The mammoth is related, but it was living up in the cold. How did it do that? You know, what changes did its body have to go through to do that genetically? And they can start to investigate these changes and sort of find out, you know, essentially look at evolution in action.
PALCA: Penn State's Stephan Schuster says he and his colleagues have already made some headway in understanding the differences between modern elephants and mammoths by comparing their DNA.
Dr. SCHUSTER: Mammoths and elephants are on the sequence level very similar; 99.4 percent is identical between the two.
PALCA: But in that point six percent difference, they've found areas that may hold the key to how animals adopt to the cold. They also found something interesting when they looked at it how elephants were evolving compared with primates like apes and humans.
Dr. SCHUSTER: We compared the rate of evolution in the primate lineage and in the elephant lineage, and we found that the evolution was twice as fast in the primate lineage.
PALCA: So things were happening more rapidly in human evolution than in elephant evolution?
Dr. SCHUSTER: That is for sure. Yes.
PALCA: Although, faster shouldn't be confused with better. Joe Palca, NPR News, Washington. Transcript provided by NPR, Copyright National Public Radio.
