In 2010, Svante Pääbo and his colleagues presented a draft version of the genome from a small fragment of a human finger bone discovered in Denisova Cave in southern Siberia. The DNA sequences showed that this individual came from a previously unknown group of extinct humans that have become known as Denisovans. Together with their sister group the Neandertals, Denisovans are the closest extinct relatives of currently living humans.
The Leipzig team has now developed sensitive novel techniques which have allowed them to sequence every position in the Denisovan genome about 30 times over, using DNA extracted from less than 10 milligrams of the finger bone. In the previous draft version published in 2010, each position in the genome was determined, on average, only twice. This level of resolution was sufficient to establish the relationship of Denisovans to Neandertals and present-day humans, but often made it impossible for researchers to study the evolution of specific parts of the genome. The now-completed version of the genome allows even the small differences between the copies of genes that this individual inherited from its mother and father to be distinguished. This Wednesday the Leipzig group makes the entire Denisovan genome sequence available for the scientific community over the internet.
“The genome is of very high quality”, says Matthias Meyer, who developed the techniques that made this technical feat possible. “We cover all non-repetitive DNA sequences in the Denisovan genome so many times that it has fewer errors than most genomes from present-day humans that have been determined to date”.