Wednesday, 8 February 2012

The First Ever Fossil Human Genome

Extracting ancient DNA from fossils at the Max Plank Institute, Leipzig,
Germany. Note: the fossil in this picture is not that of a Denisovan
In 2010, the discovery of a 50,000 year old finger bone from a completely unknown species of human was announced to the world. It caused great excitement as it could potentially clear up many mysteries surrounding human evolution and migration. Intense genetic study and comparisons quickly followed. Yet its genome had never been reconstructed and its relation to our species defined. Now scientists working at the Max Plank Institute in Leipzig, Germany, have done exactly that.

Dr Svante Pääbo and colleagues took 10 milligrams of bone from the fossil and powdered it down. Subsequently the DNA was extracted and purified in order to be fully sequenced. While ancient DNA has been the focus of Dr Pääbo's research for almost 30 years, he was able to fully sequence the Denisovan genome in less than 3 years due to the incredible advances gained from his work. In late 2010, he presented a draft version of the genome. Now the full sequence will be made available online.

The results are astonishing. 'The genome is of very high quality' said Dr. 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.' 

Analysis has shown that the Denisovans were actually more closely related to our species than Neanderthals or Homo floresiensis, the dwarf species of human discovered on the island of Flores. This holds profound implications for the story of human evolution. However their full extent will only be revealed through more genetic and fossil analysis. The group plans to present a paper describing the genome later this year. Yet they plan to make it freely available to scientists now.