Washington – Scientists said Wednesday that by using a new kind of DNA analyzer on a 38,000-year-old fragment of fossilized Neanderthal bone they had reconstructed a portion of that creature’s genetic code – a technological tour de force that has researchers convinced they will soon know the entire DNA sequence of the closest cousin humans ever had.
Such a feat, unanticipated even a few years ago, could tell a lot about what Neanderthals were like, from their hair and skin color to their relative facility with language.
It could also clear up what sort of relationship existed between them and the first modern humans – including whether the two tribes continued to interbreed after they diverged onto separate evolutionary trajectories.
Perhaps most tantalizing, the newfound capacity to reconstruct prehistoric DNA should allow scientists to home in on the less than one-half of 1 percent of the human genome that is expected to be different from that of Neanderthals, who went extinct 30,000 years ago.
Those differences, scientists said, essentially spell out in biological terms what makes humans human.
The new findings, by research teams in Germany and California, “are perhaps the most significant contributions published in this field since the discovery of Neanderthals 150 years ago,” wrote David M. Lambert and Craig D. Millar in a commentary in the journal Nature, which along with the journal Science is publishing the work this week.
Lambert and Millar, who were not involved in the work, are experts in molecular evolution at universities in New Zealand.
As the most closely related and recently departed members of the human family tree – and as the widely recognized, boney-browed icons of stonier times – Neanderthals have long fascinated scientists and armchair paleoanthropologists alike.
They and their counterparts – our human forebears – started as equals hundreds of thousands of years back, but took very different paths.
One line went on to develop all that human culture is today, from haute couture to DNA synthesizers.
Die-outs mysterious
Some say climate change killed the Neanderthals. Others blame modern humans for their extinction.
The other, while not as primitive as often described, mysteriously disappeared in a wave of die-outs that started in Western Asia about 45,000 years ago and ended with their extinction in Europe about 15,000 years later.
Some say climate change did them in. Some blame the modern humans who were expanding throughout Europe at the time and who, thanks apparently to some fortuitous genetic mutations, were enjoying an intellectual and socio-cultural awakening.
Prehistoric bones are heavily contaminated with the DNA from bacteria, as well as with modern human DNA from the scientists who discovered and handled them. That is one reason why no extinct animal has ever had its genome fully sequenced.
But the technology for detecting, analyzing and reconstructing disintegrated DNA has evolved at a stunning rate. As part of an ongoing, ambitious effort to catalog every life form on Earth, companies have developed machines that can tell whether a snippet of DNA came from the same organism as another snippet – and if so, whether the two DNA fragments were once attached to one another.
Stitch by stitch, an organism’s genome, or complete genetic code, can quickly come into view.
Scientists have already identified a few fortuitous genetic glitches they suspect may have helped launch humans to global dominance even as our beetle- browed sidekicks got mired in an evolutionary dead end.
One of those mutations, in a gene called FOXP2, may have facilitated language. Another by the name microcephalin may have been a driving force behind the big increase in brain size that occurred in humans.
Until now, the only Neanderthal DNA that had given up its secrets to scientists were bits of so-called mitochondrial DNA, which is of limited value because it does not contain genes involved in physical appearance, intelligence, or language.
“Having a Neanderthal genome will throw light on our own evolution, by allowing a three-way comparison of the genetic blueprints that produced Neanderthals and that today produce us and our closest living relatives, the chimpanzees,” said Chris Stringer, human origins research leader at London’s Natural History Museum.
