Genomic "time machine" may pinpoint divergence of human and Neandertal

A short, fossilized femur from a 38-year-old Neandertal, which sat untouched in a museum in Zagreb, Croatia, could lead to the first full genome sequence of Homo sapiens's closest relative and help scientists understand what is special about humans, say teams that published analyses of two partial sequences of Neandertal DNA in this week's issues of Science and Nature. "We're at the dawn of Neandertal genomics," proclaims Edward Rubin, genomics division director at the Lawrence Berkeley National Laboratory and lead author of the paper in Science. "In the next few years, using advances in DNA sequencing that's occurring, there's no question that we're going to have a Neandertal genome." ...

According to Rubin, the sequences provide the beginnings of a "DNA time machine" that will help update anthropological inferences about human and Neandertal populations. Among the lingering questions is whether the two populations intermixed after humans migrated out of Africa and encountered Neandertals in Europe 30,000 to 40,000 years ago. (Just this month two studies, from Washington University in St. Louis and the University of Chicago, suggested that indirect evidence from human DNA indicates intermingling occurred.) Both Rubin and Pääbo report finding no evidence of mixing. "We don't exclude it," Rubin says. "Clearly, as we go further into the future and read more, we may see evidence of that." Erik Trinkaus, a physical anthropologist and lead author of the Washington University study, believes Rubin's and Pääbo's results do not preclude his hypothesis. He says that there are two different questions regarding population mixing: Did it occur 40,000 years ago? And, do 21st-century Europeans carry distinctively Neandertal genes? "They are attempting to answer the second question and make a statistical inference back to the first question," Trinkaus explains.

•	Genomic "time machine" may pinpoint divergence of human and Neandertal Scientific American, Wednesday, Nov. 15, 2006