Oldest Human DNA Contains Clues To Mysterious Species 93
sciencehabit writes "Analysis of the oldest known genetic material ever to be recovered from an early human reveals an unexpected chapter in the story of human evolution. Researchers extracted mitochondrial DNA from the femur of a 400,000-year-old hominin found in the Sima de los Huesos ('pit of bones'), an underground cave in the Sierra de Atapuerca in northern Spain. Because the early hominins looked a little like Neanderthals, researchers expected their mitochondrial DNA to share a common ancestor. However, mitochondrial DNA from the Spanish hominin was found to share a common ancestor with an enigmatic eastern Eurasian sister group to the Neanderthals, the Denisovans."
Very interesting, but (Score:5, Interesting)
1. They had problems with modern human DNA contamination (not sure why they couldn't get everything clean but since they're the leading edge lab in this sort of thing, it must be a real issue).
2. They had to limit analysis to fragment lengths around 45 base pairs to avoid this contamination. That's tiny compared to what one normally uses.
3. They only had enough to sequence the mitochondrial DNA.
4. It's only one person.
So, it's confusing but it seems from the outside to be due to a limited data set. Now, this sort of thing is at the limit of our current technology and the lab is working to replicate and amplify the data (and work on the somatic genome). So stay confused and stay tuned.
Re:Very interesting, but (Score:5, Interesting)
And one other thing, if anybody out there knows:
They eliminated modern contaminating DNA by analyzing only DNA segments with uracil, a base usually found in RNA and a signature of older, degraded DNA.
Uracil is a modified Thymine, in vivo DNA where uracil is incorporated [scienceinschool.org] into the chain is repaired by a specific enzyme. Does the Thymine naturally degrade to Uracil over time?