Unravelling the DNA of our ancient relatives
17 November 2006
Scientists have completed their first ever detailed investigation of DNA from our closest ancient relative, Neanderthal man. The results, from a 38,000-year-old fossil Neanderthal, reveal exciting new insights into our own evolution.
Antenna investigates...
This story was published in Nature on 16 November 2006.
Image: Valley Anatomical Preparations
Neanderthals were prehistoric humans who evolved from the same ape-like ancestors as we did. They are our closest ancient relatives. But although they were around at the same time as early modern humans, they disappeared around 30,000 years ago.
Scientists think Neanderthals may have looked like this.
Now two teams of scientists from different sides of the Atlantic have worked together to sequence ancient Neanderthal DNA and compare it to our own.
They hope that by studying Neanderthal DNA we can learn more about the relationship between us and our ancient cousins, giving us clues about our own evolution and what makes us unique.
The Neanderthal bone was discovered in Vindija Cave in Croatia in 1980, but has been sitting in a museum box until now.
Image: Johannes Krause, MPI-EVA
The scientists' first step wasn't easy though: they had to extract DNA from the bone of a Neanderthal man who died over 38,000 years ago in a cave in Croatia. Then they used a radical new sequencing technique to unravel its genetic code. |
The scientists took a sample of the bone and extracted the DNA from it. They had to wear special gloves to make sure their own DNA didn't contaminate the bone.
Image: Johannes Krause, MPI-EVA
The teams faced big problems trying to make sure the DNA they used was really from Neanderthals and didn't have other DNA mixed up with it. |
'What happens is that the ancient skeleton spends 40,000 years at the back of the cave and other things are growing on this nutrient-rich source,' explains Eddy Rubin, who led the American team.
'You come back in 40,000 years and what you have is mostly DNA from these other things that have been growing on it, like bacteria and plants, and in addition there's a bit of Neanderthal.'
Eddy Rubin, Genomics Division, Lawrence Berkeley National Laboratory
Image: Eddy Rubin
Getting round this problem needed a clever trick or two...
'We filtered out the Neanderthal sequence from the environmental junk by using the human genome sequence as a reference - because they're so closely related we can fish out the DNA that looks the same, a bit like using a magnet,' says Adrian Briggs, who was part of the German research team.
Adrian Briggs, Max Planck Institute for Evolutionary Anthropology
Image: David Wrangham
'We also had to be careful that there was no modern human DNA contaminating the sample, but we managed to find a bone where there was 95-99% Neanderthal DNA.'
So far the scientists' hard work seems worth the trouble...
'By comparing the entire Neanderthal sequence that we had to the human sequence we saw that both were very close to each other, from 99.5 to almost 99.9% identical,' says Eddy Rubin.
SSPL
'When we look at these two genomes we can also estimate that the DNA of humans and Neanderthals diverged from each other around 500,000 years ago,' adds Adrian Briggs.
'This is slightly closer than expected, but these results are only preliminary. At the moment we have so little data that nothing's crystal clear yet.'
The results are exciting though: 'They suggest that large amounts of ancient and extinct genomes can be recovered. This opens up the entire field of ancient genomics,' says David Lambert, an evolutionary biologist who works with ancient DNA.
David Lambert, Allan Wilson Centre for Molecular Ecology and Evolution, Massey University, New Zealand
David Lambert
So what's next?
The scientists are now planning to sequence the full Neanderthal genome, which could help them to answer important questions about our own evolution, including when we evolved complicated behaviours such as language.
'I'm confident that we'll have a first draft of the whole Neanderthal genome in the next two years. This will be the first time anyone has sequenced the genome of an extinct species,' says Adrian Briggs.
'I think it's an incredibly exciting project and the speed in which it's been moving is amazing. Even though we haven't got all the answers yet, that it's even possible is pretty cool.'
Adrian's team in Germany
Image: MPI-EVA