Scientists Finish First Draft Of Neanderthal Genome
Scientists in Germany say they have drawn up a map of about 60 percent of the genetic "letters" in the genome of Neanderthals. The map is expected to shed light not only on what kind of creatures they were, but also what genetic differences allowed humans to leave Neanderthals in the evolutionary dust.
Neanderthals are generally considered to come from the shallow end of the Homo gene pool — an evolutionary experiment that split off from the lineage that led to modern humans and then gave up the ghost about 30,000 years ago.
The new gene map, which is the result of two and a half years spent analyzing a tiny fragment of Neanderthal bone from Croatia, suggests that humans and Neanderthals began to diverge genetically from a common ancestor about 800,000 years ago. The two populations co-existed but were genetically distinct by 300,000 years ago, according to the scientists.
Biologist Svante Paabo led the research team at the Max Planck Institute in Leipzig, Germany. "What we can now do is look at all those genetic changes on the lineage to us, and divide them up among those that happened before we diverged from Neanderthals and those that happened after," Paabo says.
Because Neanderthals were our closest relative during our evolutionary journey, differences between human and Neanderthal genetics could tell us what genes made us distinctly human. Rick Potts, head of the Human Origins Program at the Smithsonian Institution, says scientists will want to look especially hard at genes from the two species that affect brain function.
"Did they think differently?" Potts says. "The parts of the brain that are associated with social life in humans' social interaction — were they different from modern humans?"
Already, the Max Planck team has found signs of two genes that Neanderthals and modern humans might have shared: one that's thought to confer language ability, and another that makes adults unable to digest lactose in milk.
One controversial hypothesis about the two species that has not, so far, been illuminated by the gene map is if humans and Neanderthals ever interbred.
The scientists announced their findings at a meeting in Chicago of the American Association for the Advancement of Science, and plan to submit them to a scientific journal in the near future.
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STEVE INSKEEP, host:
Now let's talk about another thriller. Some new DNA evidence will ask if we've unfairly stereotyped the Neanderthal. The word Neanderthal, which you might say Neanderthal, conjures up an image of a brutish, primitive fellow, a failed evolutionary experiment, but now scientists in Germany are almost done with a map of the Neanderthal's DNA. NPR's Christopher Joyce has this story on the Neanderthal code.
CHRISTOPHER JOYCE: Neanderthal's may not have been our direct ancestors but before they died out 30,000 years ago or so, they were our closest living relatives. Svante Paabo, who led the German team from the Max Planck Institute in Leipzig, says the genome map is immensely important.
Mr. SVANTE PAABO (Biologist): The attraction of getting the Neanderthal genome is that it's our closest relative in all categories.
JOYCE: And, he says, mapping the Neanderthal code will eventually tell us as much about humans as it will about Neanderthals. The map started with a fragment of bone, carefully extracted from a fossilized Neanderthal skeleton from a cave in Croatia. The bone was over 33,000 years old. The scientist spent two and a half years extracting DNA from that bone and a few other precious specimens. This week, they have announced that they have mapped most of the genome. What does it tell them? At a press conference in Leipzig, Paabo says it tells them when human and Neanderthal populations stood apart.
Mr. PAABO: We diverged maybe something just like 300,000 years ago from the Neanderthal.
JOYCE: Genetically though, humans and Neanderthals started drifting away from a common ancestor long before that. And now, scientists can get a before-and-after look at how these two close relatives changed once they diverged from each other genetically.
Mr. PAABO: So what we can now do is look at all those genetic changes on the lineage class, and divide them up among those that happened before we diverged from the Neanderthals and those that happened after.
JOYCE: Neanderthals and humans turn out to be less than 1 percent different genetically. Among the genes they apparently shared before the split is one that creates an intolerance in adults for lactose in milk. It was only in the past 10,000 years or so that modern adult humans, mostly in Europe, evolved a tolerance for lactose, according to Paabo. Another possibility: the Neanderthal map showed features that suggest Neanderthals and modern humans might have shared a gene thought to confer language ability. Team member and biologist Ed Green(ph) says those are the kind of discoveries the map could reveal once it's finished.
Mr. ED GREEN (Biologist): The big, longer-term goal is to use the Neanderthal to find the changes that happened in our genome very recently, even after we split from Neanderthals. And these, then, will be candidates for human specific - to underly human-specific adaptation.
JOYCE: It gives us clues to what makes us peculiar, what makes us human.
Mr. GREEN: Yes, because Neanderthals are our closest extinct relatives, they kind of define what makes us human.
JOYCE: Anthropologist Rick Potts, who runs the Human Origins Program at the Smithsonian Institution, says he would like compare Neanderthal and human genes that control the brain.
Mr. RICK POTTS (Smithsonian Institution): Did they think differently? There is parts of the brain that relate to human social life and social interaction. Were they different from modern humans?
JOYCE: The new data could cast light on another controversial hypothesis about Neanderthals: whether they interbred with humans. So far, the team says, there's no significant evidence in the genome that they did. The team announced their findings at a meeting of the American Association for the Advancement of Science, and they plan to publish their results soon.
Christopher Joyce, NPR News. Transcript provided by NPR, Copyright National Public Radio.
