Wednesday, December 4, 2013

Very old DNA

Sima de los Huesos, the "bone pit," is a cave site in Northern Spain that has yielded the world's largest assembly of Middle Pleistocene hominin fossils, consisting of at least 28 skeletons, which have been excavated and pieced together over the course of more than two decades. The fossils are classified as Homo heidelbergensis but also carry traits typical of Neandertals. Until now it had not been possible to study the DNA of these unique hominins.

A team from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, has developed new techniques for retrieving and sequencing highly degraded ancient DNA. Together with a Spanish team of paleontologists they sampled two grams of bone powder from a hominin thigh bone from the cave. They extracted its DNA and sequenced the mitochondrial genome. By comparing those DNA sequences those of Neandertals, Denisovans, present-day humans, and apes, the researchers calculated that the Sima hominin lived about 400,000 years ago. They also found that Sima hominin shared a common ancestor with the Denisovans, an extinct group from Asia related to the Neandertals, that lived about 700,000 years ago. This find was rather unexpected since skeletal remains carry some Neandertal-derived features.

What I find most intriguing is the simple fact that the colleagues were able to determine an almost complete mitochondrial genome sequence of a 400,000-year-old representative of the genus Homo not buried (and preserved) in Permafrost. I am thinking of all the type specimens we try to obtain DNA Barcodes from. They are much younger but most likely less well preserved. Nevertheless, worth to have a close look at all the methods and tricks used to come up with a mitochondrial genome that old. One thing for sure - they were able to retrieve the full DNA Barcode - just checked it.

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