After a bit of teasing in the blogosphere that the draft sequence of the Neanderthal genome would be released in time for Charles Darwin’s birthday this week, I was eagerly looking for a paper. Instead what I find are three news articles in Science, one describing some of the outcomes of the work, and two setting it in context. Some quotes:
Initial comparisons with our own 3 billion bases indicate that a mere 1000 to 2000 amino acid differences, as well as a yet-unknown number of non-coding changes, do that job. For comparison, about 50,000 amino acid differences separate us and chimpanzees.
It’s interesting to see just how similar we are, and it’s not clear to me how this supports (or doesn’t support) the status of neanderthals as a species distinct from Homo sapiens. Incidentally, the samples from which the DNA was extracted are about 38,000 years old (which is from the most recent Neanderthal remains), and sequence has been determined from the remains of two females, presumably with some relationship
For now, there’s not enough sequence to do more than make a rough sketch of Neandertals. "Many gaps and errors are expected," says Lalueza-Fox. To be certain about the order of the bases, sequencers need to determine each base at each location multiple times–and Pääbo has only enough sequence to cover the genome one time over. In total, the team has sequenced 3 billion bases, not quite the length of the whole genome. But some bases were sequenced repeatedly, and some spots were missed entirely. All together, Pääbo estimates they have covered 60% of the entire genome.
So, really we’ll need to wait a while before all the data are available to be assessed. There’s always a danger that release of research results via press release and news briefings gives a "spun" view of the findings. I’m not trying to impugn the researchers here, it’s just that the interplay between those trying to report the news and who have an agenda to write exciting stories; and those who’s research efforts are being reported on cannot be easy at all times.
Citations (subscription required):
Pennisi (2009) Tales of a Prehistoric Human Genome. Science 323; 866 – 871 DOI: 10.1126/science.323.5916.866
Pennisi (2009) Wanted: Clean Neandertal DNA Science 323; 868 DOI: 10.1126/science.323.5916.868
Balter (2009) A Neandertal Primer. Science 323; 870 DOI: 10.1126/science.323.5916.870
The story is featured in the Science podcast for 13th February, which is freely available.