Working with just a fragment of a finger bone, German scientists have decoded the entire genome of an extinct human identified as a member of the Denisovans, an Asian group related to the Neandertals. Together, the Denisovans and the Neandertals are our closest extinct relatives. The scientists believe their genome is of such high quality it has fewer errors than most sequences of modern-day humans. They published the genome on the internet this week.
The fragment of finger bone, which offered only 10 milligrams of material for the scientists to work with, had been discovered in Denisova Cave in southern Siberia.
In 2010, Svante Pääbo and his colleagues at the Max Planck Institute for Evolutionary Anthropology, in Leipzig, published a draft version of the genome. This showed the DNA came from a previously unknown group of humans now known as the Denisovans. The draft was sufficient to establish relationship of Denisovans to Neandertals and present-day humans, but was not good enough to enable study of how parts of the genome evolved.
Since then, using new techniques that allowed them to sequence every position in the genome 30 times over (in the draft version this had been done only twice over), the team have decoded a completed version of the genome that distinguishes even the tiniest differences between the father’s and mother’s copies of each gene.
The genome represents a big step forward in the study of extinct humans: it is the first complete genome sequence of an archaic human group.
On Wednesday, Pääbo and colleagues published the entire genome sequence on the internet, making it available to other scientists.
Pääbo told the press:
“We hope that biologists will be able to use this genome to discover genetic changes that were important for the development of modern human culture and technology, and enabled modern humans to leave Africa and rapidly spread around the world, starting around 100,000 years ago.”
Matthias Meyer, who developed the new methods that made the detailed sequencing possible, said:
“The genome is of very high quality. 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.”
The group plans to present a paper on their work later this year, but they wanted to make their genome freely available sooner.
“We believe that many scientists will find it useful in their research,” said Pääbo.
They expect the genome will reveal new secrets about the Denisovans and Neandertals.
Pääbo and his team have been studying ancient DNA for nearly 30 years.
The archaeological excavations at Denisova Cave are unique in that they contain cultural layers that suggest humans first occupied it about 280,000 years ago.
Professor Anatoly Derevianko and Professor Michail Shunkov, from the Russian Academy of Sciences, discovered the finger bone in 2008, in a layer that is thought to date from 30,000 to about 50,000 years ago.
Click here for more information on the genome and where you can get a download of the sequence.
Written by Catharine Paddock PhD