for National Geographic News
Modern humans' closest relatives, the Neandertals, broke off from the family tree about 500,000 years ago, according to one of two new studies that analyzed DNA from the extinct species Homo neandertalis.
Nuclear DNA from a 38,000-year-old Neandertal (often spelled Neanderthal) fossil leg bone from Croatia was sequenced and compared to DNA from modern humans and chimpanzees.
The findings, published today in the journal Nature, also suggest that the entire Neandertal population was derived from a relatively small ancestral group of 3,000 individuals.
The second study, released simultaneously by the journal Science, analyzed DNA from the same ancient Croatian bone, revealing for the first time that modern humans and Neandertals share 99.5 percent of their genetic makeup.
But their analysis didn't find evidence that modern human and Neandertal DNA mixed, seeming to counter recent conclusions that Neandertals interbred with humans to the point of total absorption, leading to their extinction.
Overall, the dual projects signal the dawn of Neandertal genomics, says Edward Rubin, director of the U.S. Department of Energy Joint Genome Institute and co-author of the Science study.
"In many ways it will change some aspects of anthropology," Rubin said. "We're never going to bring [Neandertals] back to life, but we will be able to compare [the species' genetics] to the human genome."
The Nature study team used an advanced new machine to perform high-throughput nuclear DNA sequencing.
Using this method, the team, led by Richard Green of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, was able to isolate about one million DNA base pairs, creating the beginnings of a Neandertal genome "library."
Base pairs are the "letters" of the genetic alphabet that are combined in DNA as genes to code for everything from hair color to body shape (get an overview of human genetics).
"Neanderthals are the hominid group most closely related to currently living humans, so a Neanderthal nuclear genome sequence would be an invaluable resource for annotating the human genome," the Nature study authors wrote.
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