Complete Neanderthal Genome Sequenced
Initial analysis suggests that up to two percent of the DNA in the genome of present-day humans outside of Africa, originated in Neanderthals or in Neanderthals' ancestors. This new data suggests evolution did not proceed in a straight line. Rather, evolution appears to be a messier process, with emerging species merging back into the lines from which they diverged.
Goers: Researchers have produced the first whole genome sequence of the Neanderthal genome. Neanderthals diverged from the primate line that led to present-day humans some 400,000 years ago in Africa. Dr. Jim Mullikin is the Acting Director of the NIH Intramural Sequencing Center and a computational geneticist. He recently worked with an international team of scientists to sequence the complete genome of the Neanderthal.
Mullikin: It has been an amazing journey with the group, led by Svante Pääbo at the Max Planck Institute in Leipzig, Germany.
Goers: The researchers compared DNA samples from the bones of three female Neanderthals who lived some 40,000 years ago.
Mullikin: And they have been in these caves, buried under layers and layers of sediment for all those tens of thousands of years. And, when they unearthed those bones, they used a clean room environment, they were able to take some of the bones and take small bits of the bones and make it into a powder. And from that, they could extract the DNA from the powder material, and some of it, not much of it, but some fraction of it, was actually from that the Neanderthal that died in that position.
Goers: Despite being the closest distinct relative of modern humans, one of the obstacles in decoding the Neanderthal gene was the possibility of contamination of the sample with modern human DNA. Dr. Mullikin explains:
Mullkin: So they had to make extra special care in handling the DNA, prior to sequencing it. They were short fragments of DNA, that had been altered by the eons of time that they had been underground. They change in a distinctive pattern so that we know which ones are real, that are the old pieces from the ones that might be contamination. But contamination was one of the main focuses of understanding what might be contaminate and what was real Neanderthal DNA. We tried to remove as much of the contaminate as possible from the sequence. We got it down to below 1 percent.
Goers: The researchers compared DNA samples from the Neanderthal bones to samples from five present-day humans from China, France, New Guinea, southern Africa and western Africa.
Mullkin: After we were able to sequence it and essentially map it back to other closest living relatives, homo sapiens and chimpanzees, we aligned the sequence back to both of those species and were able to find the differences that are unique to the Neanderthal, and more important, what are similar between Neanderthal and modern humans and modern chimpanzees.
Goers: Dr. Mullikin and his fellow researchers found two percent of the genome similar to the modern humans in the study not from Africa. They hypothesize that humans migrating from Africa bred with Neanderthals in Europe leading to the Neanderthal DNA present in some humans today. For more information on the Neanderthal genome, visit www.genome.gov. This is Elizabeth Goers, National Institutes of Health, Bethesda, Maryland.