Tuesday, February 1, 2011

Another Human Ancestor Discovered?


A 30,000 year old fossil of a finger bone and a tooth from a human precursor was found in Siberia in 2008, and their genomes sequenced. The finger appears to be from a female who lived in the same time as the Neanderthals, and the tooth from a similar individual. Scientists are classifying this recently discovered group as Denisova hominin, after the cave the remains were uncovered in. (Hominin is a relatively new grouping currently used to classify humans and their ancestors.) The theory is that Denisovans and Neanderthals evolved from a common ancestor, independently of one another, with Denisovans evolving into Melanesians and Neanderthals evolving into Eurasians.

Today’s biotechnology allows for more accurate classification of ancient species, because a sequenced genome is strong evidence for where the organism should fall in the cladogram. The DNA had 2 enzymes added to it and was run through the polymerase chain reaction 101 times to produce a large enough quantity of the ancient DNA for proper analysis. As these technologies are applied to more species, the traditional cladograms need to be modified. The mitochondrial DNA(mtDNA) was sequenced and analyzed against human DNA and appeared very similar, so the nuclear DNA was sequenced as well, adding more evidence to their relationship. The mtDNA for Denisovans is not as closely related to human mtDNA as that of the Neanderthal, but their nuclear DNA is about as similar as the Neanderthal’s. However, taxonomists are waiting on more evidence before declaring Neanderthals or Denisovans as actual species.

Who knows? Maybe we have even more ancestors than this!

Check it out at http://www.nature.com/nature/journal/v468/n7327/full/nature09710.html.

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