German scientists have created a new technique for sequencing old and degraded DNA, allowing them to sequence the genome of an archaic Siberian girl. The new method works by creating multiple copies of the same strand of DNA, amplifying over 99 per cent of the genome ten-fold while maintaining a level of accuracy comparable to the genetic map created by the DNA of a living person.
Scientist Matthias Meyer and his team from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have catalogued the differences between this old genome and modern human DNA. The ancient DNA was acquired from the 50,000 year-old finger bone of a resident of Siberia’s Denisova Cave.
The Denisovans were found to be close relatives of the Neanderthals, interbreeding with the ancestors of some living humans at a low rate. Genetic analysis of the genome reveals that the Denisovans had differences in genes currently associated with the wiring of the nervous system, including a gene implicated in autism and the FOXP2, gene which has been implicated in speech disorders. These new findings suggest that Neanderthals differed from modern humans in their neural capacity for language. This breakthrough came about because the researchers were working with single strands of DNA instead of double strands. Old DNA is prone to breaking up into single strands which are difficult to sequence with current techniques. Meyer overcame this hurdle by binding special molecules to the ends of the single strands of DNA that held them in place while the enzymes replicated them. The new technique is simple and cheap enough to be used in wide-scale research, and further sequencing of more human fossils is already underway.
