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Scientists have begun to unravel the genetic secrets of the Neanderthal, our low browed, barrel chested relative. They've deciphered part of the genetic code of a male Neanderthal who died approximately 38,000 years ago. The work helps pin down when Neanderthals and modern humans went their separate ways.
But as NPR's Joe Palca reports, the results are most important for another reason. They suggest that sequencing all three billion DNA letters of the Neanderthal genome is an achievable goal.
JOE PALCA: It's amazing that a strand of DNA can remain intact for tens of thousands of years. But it can and that means scientists like Eddie Ruben can try to read the genetic code buried in that ancient DNA. Ruben is director of the Department of Energy's Genome Institute.
A few years ago Ruben asked scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig if he could join their efforts to sequence Neanderthal DNA. The idea that you could parent the genome of an extinct caveman was too tantalizing to pass up.
The Max Planck gang said sure, but first they told Ruben he had to get some practice working with ancient DNA. So they sent him some material from the skeletal remains of a cave bear.
Dr. EDDIE RUBEN (Department of Energy Genome Institute): The cave bear has lived about the same time as Neanderthals. But the good thing about cave bears is there are lots of them and you can get lots of material.
PALCA: Ruben was able to read DNA sequences from the cave bear, so the journal scientists sent him some ground up Neanderthal bone, the same bone they were using to get DNA from.
Dr. RUBEN: One of the problems in ancient DNA is contamination. You always worry about whether there is a lab worker sequence in there instead of that Neanderthal sequence.
PALCA: Ruben says in this case, the bone was remarkably free of human contamination. Max Planck Institute Scientist Richard Green says there's another huge problem when trying to get Neanderthal sequence from a Neanderthal bone.
Dr. RICHARD GREEN (Max Planck Institute): The DNA extract that we get has DNA from not only the Neanderthal who owned that bone originally, but also DNA from all the bacterial species that have colonized this fossil since the Neanderthal died.
PALCA: In fact, says Green, for every one fragment of DNA that came from a Neanderthal, there are 20 that came from bacteria, and that means a lot more work.
Dr. GREEN: We have to sequence 20 times more than we would if we were getting all the Neanderthal's.
PALCA: Now you've got one million base pairs sequence but that leaves about 2,999,000,000 left.
Dr. GREEN: Yes.
PALCA: And yet you think you're going to be able to go ahead and do the rest of it?
Dr. GREEN: Yes.
PALCA: Green says he and his colleagues have enough Neanderthal samples and enough sequencing power to complete a rough draft in two years. The preliminary reports on the Neanderthal genome appear in the journals Nature and Science.
Based on the data they've gathered so far, scientists think modern humans and Neanderthals diverged between 370 and 500 thousand years ago. And there are hints that at least a few modern human ancestors may have mated with Neanderthals, although for now nothing more than hints.
Richard Gibbs is head of the sequencing center at Baylor College of Medicine. He says the Neanderthal genome project is off to a good start.
Dr. RICHARD GIBBS (Baylor College of Medicine): This is a great demonstration that you can do this kind of thing, and as the (unintelligible) sometimes to point out. You have to do a whole lot more of it to get a really accurate picture, or hope of an accurate picture of what those individual genomes were really like.
PALCA: Gibbs says one of the great things about the Neanderthal genome project is it stirs the imagination. Max Planck Institute scientist Richard Green can't wait for the full sequence.
Dr. GREEN: We can compare the human genome sequence to Neanderthal and maybe find the genetic underpinning of the things that really separate humans from the Neanderthal.
PALCA: So is this the coolest thing you've ever worked on?
Dr. GREEN: I think this is the coolest thing anybody's ever worked on.
PALCA: Joe Palca, NPR News, Washington.
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