18:00 15 November 2006
NewScientist.com news service
Dan Jones
Outside the Vindija cave in Croatia (Image: Johannes Krause / Max-Planck-Institute of evolutionary Anthropology)
What are the genetic changes that set us apart from our Neanderthal cousins? Although the ancient race is long extinct, we may soon know the answers.
More than one million base pairs of fossilised Neanderthal DNA have now been sequenced – the most of any extinct organism – thanks to a new high-throughput sequencing technique well-suited to handling old, degraded DNA.
Two research teams collaborated closely on the project – the first steps towards sequencing the Neanderthal genome – in a marked difference to the competitive race to for the human genome.
Both teams used the same 38,000-year-old Neanderthal specimen, discovered in Croatia, from which to extract DNA and report their findings on Wednesday in the journals Nature and Science, respectively.
Common ancestor
The sequence suggests that humans and Neanderthals probably began to diverge about 600,000 years ago, and that our common ancestor lived in a small population comprising just 3000 individuals.
One group, led by palaeogeologist Svante Paabo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, used the rapid new "direct sequencing approach" on DNA culled from the ancient hominid’s thighbone. The technique was developed by research collaborators 45 Life Sciences, based in Branford, Connecticut, US.
The other team, led by geneticist Eddy Rubin at the Lawrence Berkeley National Laboratory, Walnut Creek, California, US, used a more traditional sequencing method involving cloning DNA using bacteria to generate 630,000 base pairs of the Neanderthal sequence.
Time difference
The studies only explored a tiny fraction of the full genome, and so the insights they provide are limited, so far. But both teams were able to use their results to estimate how long ago humans and Neanderthals shared a common ancestor.
Paabo’s group puts the date at around 516,000 years ago, while Rubin’s team reaches a slightly older date of 706,000 years ago. Both estimates have large errors of margin that in fact overlap, so the dates are broadly compatible.
One of the major problems confronting efforts to sequence such ancient DNA is contamination, both from microbial DNA and, more significantly, from modern human DNA, which could be confused with Neanderthal sequences. Researchers in both teams used a number of tests to ensure that they were working with genuine Neanderthal DNA, however.
“This is proof of principle that we can recover nuclear genome sequences from Neanderthals,” says Richard Green, one of Paabo’s team. We should have the full genome sequenced within two years," he says.
Journal reference: Nature (DOI: 10.1038/nature05336), and Science (vol 314, p 1113)