Nearly 500GB of data from the DNA of an ancient girl has been published for the first time. The genetic information - made available for wider analysis by intrigued boffins - was extracted from her finger bone and tooth, which were unearthed in the Denisova Cave in Siberia in 2008.
“It's a tiny little bone,” said Professor Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology in Leipzig. “The whole fragment was 16 milligrams.”
A draft, incomplete version of the cave girl DNA – which has come to be known as Denisovan after the cave where the samples were found – was published in December 2010.
The remains are estimated to be 30,000 to 50,000 years old and show that Neanderthals and modern humans were not the only hominids living at the same time.
The discovery also found that Denisovans interbred with Homo sapiens, with 5 per cent of their DNA living on in modern humans. Their descendants today live in Papua New Guinea, east Indonesia, Australia, Fiji and Polynesia.
It is only now that sequencing technology is capable of producing the high level of accuracy needed for further research. That is thanks to the work of Matthias Meyer, who has developed a new way of ensuring that DNA sequencers such as the Illumina Genome Analyzer IIX, the one used by Pääbo's team, need only 10 per cent of the sample in order to sequence it. Meyer's breakthrough is an improvement in efficiency on previous methods by a factor of ten.
Working with the new genetic data, boffins around the world are now attempting to nail down the fine differences between the DNA of Denisovans, Neanderthals and modern humans.
Since the first draft in 2010 “we have sequenced very much more – every position in the genome about 30 times over,” explained Pääbo. He said that his team would publish a scientific paper later this year. In the meantime, “we wanted to make [the genome data] available to the world because people are working with it”.
Until now, geneticists looking for how certain genes became distinctly human could only compare DNA from modern humans with that of chimpanzees, separated from humans by around seven million years of evolution.
The Denisovan sample narrows the difference to only 200,000 or 300,000 years. It is hoped that scrutinising this slim difference will reveal the histories of certain genes such as FOXP2, one of the many genes associated with language. Apes do not carry FOXP2, but both Neanderthals and modern humans do – and so did the Denisovans.
Pääbo is satisfied that the DNA data will not be used to clone a Denisovan. “It's technically impossible,” he said. “We have only 70% of the genome.” The bone samples found in the Siberian cave are so old that much of the DNA is lost.
Today's technology can fill in some of the gaps, but not all. And in any case, Pääbo says that resurrecting a Denisovan would be “ethically indefensible”. ®