- Read more about this story at ScienceNews.
- More from the Spittoon on ancient DNA:
mtDNA) suitable for sequencing.Their results, published online today in the journal Nature, show that compared to present-day humans, mtDNA from the so-called “Denisova hominin” contains twice as many differences as do mtDNAs from Neanderthals. From this the researchers conclude that the Denisova hominin was a member of a previously unknown species of human ancestor. Further analysis allowed them to estimate that the most recent common maternal ancestor shared by all three species lived about one million years ago.“Their discovery is remarkable not just for the insight it gives into the human past. For the first time a hominin has been described, not from the morphology of its fossilized bones, but from the sequence of its DNA,” wrote Terence A. Brow, in a News & Views article that accompanied the Nature study.There is evidence that both Neanderthals and anatomically modern humans were in the area of the Denisova cave at around the same time as the individual whose mtDNA was sequenced in the current study. This suggests that each wave of hominins that moved out of Africa and into Eurasia did not replace the last. Instead, multiple lineages coexisted for long periods of time.More work will be needed to definitively determine the relationship of the Denisova hominin to Neanderthals and modern humans. Ongoing research is attempting to isolate nuclear DNA for further comparisons and to look for evidence of interbreeding.Update 3/29/10: There’s quite a bit of discussion about whether or not the Denisova hominin really is a distinct species. A good place to learn more about the debate is Carl Zimmer’s blog The Loom. The Atavism also has a post about this topic.