A known paleogeneticistas managed to push back in time, in spectacular fashion, the limits of techniques for extracting and sequencing DNA coming from fossil remains of early humans. The findings are published in the journal Nature on Thursday, advances the Público newspaper.
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Svante Pääbo
of the Max Planck Institute in Leipzig (Germany) and his colleagues had already achieved with techniques developed by them, extract and read the full genomes of these archaic humans.
But now
gave a huge time warp in the study of the genetics of human evolution. “We read the genetic material five to ten times older than what we looked at before,” said Pääbo to Nature.
not yet been possible to read the entire DNA of primitive man who lived hundreds of thousands of years in a cave in Spain – and, indeed, will take some time to refine the techniques to get them done. But they could, instead, deciphering mitochondrial DNA of this kind of remote humans. Mitochondrial DNA is a little DNA maternally mediated and contained in the mitochondria (cell batteries). And because each cell has hundreds of mitochondria, the DNA is much more abundant than the rest of the genetic material (the so-called “nuclear DNA”) that facilitates the extraction and analysis. Anyway, there are only a few years, with fossils of this age, this last feat of Leipzig team would have been impossible.
Scientists extracted DNA from a tiny amount of bone powder – (1.95 grams only) harvested sticking a human femur with nearly 400,000 years, discovered in 1990 in the cave of Sima de Los Huesos (Spain) , a site that contains “the world’s largest collection of fossils of early humans in the Middle Pleistocene,” they write. This site has been excavated, over more than two decades, the team of Juan-Luis Arsuaga, Universidad Complutense de Madrid, who also signs the results.
is thought that the femur belonged to an individual of the species Homo heidelbergensis a primitive man with some distinctive features of Neanderthal type morphology at the level of the teeth, jaw face. Therefore, the most widely accepted idea is that men Sima de los Huesos are probably direct ancestors of Neanderthals, says Pääbo.
Not only that they have beaten – and by far – the record time in the analysis of a fossil human DNA, the almost complete sequencing of the mitochondrial DNA of this ancient bone hid a large genetic surprises revealed when scientists compared this DNA with Neanderthals, Denisovans, great apes and modern humans. Because, contrary to what was expected, the mitochondrial DNA of man the Spanish cave be revealed closer to the mitochondrial DNA from Denisovans Asians than the Neanderthals of Europe. “The fact that the mitochondrial DNA of the primitive man of Sima de los Huesos share a common ancestor with the Denisovans and Neanderthals is not unexpected, since its skeleton has characteristics derived from Neanderthals,” says Matthias Meyer, lead author of study, said in a statement at the Max Planck Institute.
course this does not mean that Denisovans have not had characteristics similar to those of Neanderthals, since little is known of their physical appearance. “We know almost nothing about the appearance of the Denisovans”, says Pääbo. “We just have its genome and huge teeth. We can only say that they should have very big mouths -., And probably very large bodies “For the past few weeks, the mystery surrounding the Denisovans is thickened with the discovery that its genome contains traces of a kind of archaic humans yet unidentified …
“Our finding raises more questions than it solves,” says Pääbo yet, “because it suggests a link between primitive men of Europe and Asia.”
There are several scenarios that could explain the puzzle that scientists describe in your article. One is that men Sima de los Huesos may be close relatives of the ancestors of Denisovans. However, “this hypothesis is remote,” they write, “because the presence of the Denisovans in Western Europe indicate an extensive spatial overlap with the ancestors of Neanderthals, raising the question of how these two groups differ genetically managed to coexist in the same territory as “. Either way, they add, “the specimen Sima de los Huesos is so old it is probably before the divergence between Denisovans and Neanderthals.”
Another possibility is that the group of Sima de los Huesos is different from either of the Neanderthals and the Denisovans – but at some point, has contributed to the mitochondrial DNA from Denisovans. However, it does not convince the authors, since “imply the emergence, independently of several morphological characteristics of Neanderthal type in a group not associated with Neanderthals.” A third scenario would still be men of Spanish cave were related to the common ancestor to Neanderthals and Denisovans. One scenario ‘plausible, but that requires an explanation for the presence of two totally divergent mitochondrial DNA lineages in the same archaic group, one of which resurfaced following the Denisovans, while the other was fixed in Neanderthals, “reads the Nature.
Finally, scientists speculate that a “gene flow, coming from another population of early humans may have introduced similar mitochondrial DNA with Denisovans of the population of Sima de los Huesos or their ancestors” – and that At the same time, the same archaic group may have also contributed with its mitochondrial DNA genes for Denisovans in Asia. “We are so close in time the common ancestral population of all these individuals it is possible that the ancestral population has mixed their genes with an even older population, such as Homo erectus, and has inherited her your mitochondrial DNA” says Pääbo .
the authors
One thing is certain, they conclude: to get untangle this part of human evolution, will have to sequence the entire DNA of the nucleus of the ancient inhabitants of Sima de los Huesos. “The ultimate answer is in the nuclear DNA, which will allow men to see if the Sima de los Huesos closest relatives are the Neanderthals, the Denisovans and modern humans,” says Pääbo. “I hope that within a year or so we have enough nuclear DNA to answer these questions.” There are 28 skeletons at Sima de los Huesos and there-some of them to end up showing your DNA …
