Team Atapuerca and the Max Planck Institute for Evolutionary Anthropology have sequenced the nearly complete mitochondrial genome of a human rest of the Femur XIII Sima de los Huesos in Atapuerca (Burgos), dated to about 400,000 years (Pleistocene mean).
Mitochondrial DNA is found in multiple copies in the mitochondria of cells and is transmitted only through the maternal line. Only in the permafrost, or frozen soil, DNA was recovered this old, but not human.
“Find a nearly complete mitochondrial genome of a human fossil from over 400,000 years ago is in itself an unprecedented success. Oldest to this is less than 100,000 years. involves a giant leap,” says the SINC paleontologist Juan Luis Arsuaga, director of the Joint Center for Evolution and Human Behavior, scientific director of the Museum of Human Evolution in Burgos and co-author of the study.
It has therefore been necessary for scientists to develop a new and advanced technology. From the methodological point of view, this technique has opened the door to future discoveries.
“We have applied techniques that we seemed unthinkable before. Specifically, this new methodology allows to work with ultrashort DNA segments, because this genetic material degrades and the chains are breaking. La Sima de los Huesos is a limit case seniority, as the segments found were very small, “adds Arsuaga.
This methodology makes it possible to recover, investigate and assemble tiny segments to construct very long DNA chains.
Relatives Denisovans in Siberia
team Matthias Meyer of the Max Planck had already sequenced the complete mitochondrial genome of a preceding bear the same site and found with human fossils.
The researchers then proceeded to compare the extracted Femur XIII of the Sima de los Huesos with the both closest living species (modern humans and great apes) as fossil mitochondrial genome. Neanderthals and Denisovans
From genetic data, researchers calculated an approximate age for the fossil of the Pit of the Bones of 400,000 years, very similar to that estimated by the same procedure for the bear. 430,000 years
Comparison of mitochondrial genome sequences revealed greater proximity fossil Sima with Neanderthals Denisovans that, contrary to expectations.
“We have concluded that the closest relative of this species from the Sima de los Huesos is in Siberia, but that does not mean that closely resemble, in fact it is estimated that would take 700,000 years to evolve separately.’re very different but with a common ancestor that had to be a species that lived in Europe and Asia in the age of vertigo “Arsuaga added.
Denisovans are considered very distantly related to Neanderthals. Just have morphological information of these individuals found in the Denisova cave in southern Siberia, so it is not possible anatomical comparisons with fossils from the Sima de los Huesos.
According to the director of the Museum of Human Evolution, evolve later Neanderthals in Europe, but at that time in the Sima de los Huesos their mitochondrial DNA was still not present or did not have all individuals.
aims Meyer, “not expected that mitochondrial DNA from the Sima de los Huesos share a common ancestor with the Denisovans instead of the Neanderthals, since the Sima fossils show traits Neanderthals” .
a scenario much more complex species
Given the age of the site, a possible scenario is that humans from Sima are related to the ancestral population from which they evolved separately Neanderthals and Denisovans.
Another possibility, researchers say, is that other than hominins transmitted mitochondrial DNA types to Denisovan hominins from Sima, or their ancestors.
“This work shows that we can now study the DNA of fossils with several hundred thousand years old, opening the possibility of knowing genes of the ancestors of Neanderthals and Denisovans. It’s tremendously exciting,” says Svante Pääbo, director of the Max Planck Institute for Evolutionary Anthropology.
The discovery points to a more complex than assumed in the Middle Pleistocene. So far very simple schemas that Neanderthals evolved into Europe and, indeed, a large scale is what happened were used.
“When you have the opportunity to go into detail shows that each European town has its own history and that different lines intersect, sometimes mixed and others are separated. few of them are extinct and others continue. Say Neanderthals are the only surviving line that reaches almost to the present day, the whole set of species that were in ancient times, “adds the scientist.
researchers begin to peek into that complexity now they have available genetic information. “We hope that future research will clarify the relationship between the Sima fossils, Neanderthals and Denisovans.”
whole team is now proposed sequencing mitochondrial DNA from other individuals of the Sima, and even recover some nuclear DNA sequences.
The site of the Sima
Sima de los Huesos is the site which provides, in one place, more fossil of a fossil hominin species. Since 1976 working in the recovery of the skeletal remains of at least 28 individuals.
are complete skeletons, but their bones are highly fragmented, dispersed and mixed, making it difficult to rebuild them.
species represented in the Sima de los Huesos sample a combination of archaic features with other incipient Neanderthals, so it is considered evolutionarily related to the latter.
particular reservoir conditions, isolated for hundreds of thousands of years ago in the depths of a karst system, have allowed exceptional preservation of human bones.
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