Paleo Patrol: Neanderthal genome offers clues on what makes us human

by Erin Wayman
Thursday, January 5, 2012

Erin Wayman (pictured in Cardiff, Wales) writes Paleo Patrol for EARTH. Spencer Wayman

Did “Clan of the Cave Bear” get it right after all?

Probably not, but at least one aspect of the ice age saga is true: Modern humans interbred with Neanderthals. In fact, for many of us, as much as 4 percent of our DNA may be Neanderthal DNA. That’s the conclusion of a group of 56 scientists who have just announced today in Science that they’ve completed a draft sequence of the Neanderthal genome.

The confirmation of human-Neanderthal mating may be the flashier part of the new study, but there is another, perhaps more subtle consequence that I find even more fascinating: The work will give researchers the opportunity to better understand what makes modern humans unique, genetically speaking, from all other species of hominins that came before us.

Researchers interested in human evolutionary genetics often compare human DNA with the DNA of chimpanzees, our closest living relatives. But when they find genetic differences between the two species, they don’t know for sure where in the hominin lineage those genetic attributes evolved. Did they initially arise in Australopithecus? In the first species of Homo? Or are they genetic characteristics that only evolved in Homo sapiens and thus distinguish us from all other hominins?

The new Neanderthal genome — actually, it’s more of a partial genome, in that researchers only sequenced approximately 60 percent of it (which is still impressive) — will allow researchers to take a crack at some of these questions. For example, researchers can scan parts of the genome where modern humans are known to differ from chimpanzees and then see what Neanderthal DNA looks like. If Neanderthals match chimpanzees, then it implies that the feature in question evolved after humans and Neanderthals split sometime approximately 400,000 years ago (the new study gives a range of 270,000 to 440,000 years ago).

The team was led by Svante Pääbo, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who is kind of like the godfather of Neanderthal genetics. They have already identified parts of certain Neanderthal genes that are different from modern humans but match those of chimps — genes related to a variety of things, including sperm, wound healing and skin. Exactly how these differences affect the function of what these genes code for — or why these changes happened — is not clear, co-author Richard Green of the University of California at Santa Cruz said yesterday at a press conference about the findings.

But the team did detect changes in modern humans' genes related to cognitive development; those changes, they say, are probably due to natural selection. That implies that the expression of those genetic traits may have given early humans evolutionary advantages. Given how much pride we humans take in our intellect, perhaps this preliminary finding isn’t all that surprising.

But this is really just the beginning of large-scale studies of Neanderthal DNA. Now that researchers have the techniques of ancient DNA analysis down, we’ll probably see a lot more studies that give us new insight on what it means to be Homo sapiens.

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