for National Geographic News
A new genetic study bolsters theories of an early human-Neandertal split and is helping scientists pinpoint what makes humans unique.
Controversy has long swirled in the scientific community over how closely the Eurasian hunters resembled modern humans, with some researchers even claiming Neandertals (often spelled Neanderthals) were actually members of our own species, Homo sapiens. (Related: "Neandertals' Last Stand Was in Gibraltar, Study Suggests" [September 13, 2006].)
A new study by geneticist James Noonan at Lawrence Berkeley National Laboratory, however, reveals that modern humans and Neandertals' most recent common ancestor probably perished about 400,000 years ago.
The research was presented earlier this month at the American Society of Human Genetics conference in New Orleans, Louisiana (get a genetics overview).
Richard Potts, director of the human origins program at the National Museum of Natural History in Washington, D.C., called Noonan's work "highly significant."
"Each part of the Neandertal genome is an archive of the similarity and distinction [between Neandertals and] all people living today," he said. "Comparison to a lineage in our own family tree helps us understand which elements of the genetic code make us human."
To obtain the raw material for his study, Noonan extracted DNA from fossilized Neandertal bones.
Combing the samples for Neandertal-specific genetic sequences was a painstaking process bogged down by large amounts of contamination.
"Most of the DNA we got was bacterial DNA from organisms that had colonized the specimens," Noonan said. "We can pick out the ancient DNA sequences because they're shorter and more degraded."
After analyzing the genetic content of the sequences, Noonan and his colleagues began cataloging them in a library similar to that used to help organize the human genome.
Initial results indicate Neandertals have contributed surprisingly little to modern humans' genetic makeup.
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