by Manuel Ansede December 4, 2013
It shows two grams of bone
used to study DNA heidelbergensis
Javier Trueba - Madrid Scientific Films
Reading a part of the genome of an individual who lived 400,000 years ago in today 'sSpain reveals an unexpected kinship with an unknown Siberian human group until 2010 and inaugurates a new era in the study of evolution A human who lived 400,000 years ago between bears and lions in what is now the Iberian peninsula has upended once again, what is known about human evolution.
The analysis of two grams of the femur, buried during all those millennia in the Sima of the Bones of the Sierra de Atapuerca (Burgos) shows that their DNA is related to Denisovans , a new group of humans discovered in 2010 from a pair of teeth and a tiny little finger bone unearthed in a cave in Siberia (Russia).
The finding is a monumental surprise. It would be like finding out of context a black person with a Basque surname, according to paleontologist example Ignacio Martínez , co - author of the research.
The human group of the Sima of the Bones, classified as Homo heidelbergensis , has Neanderthals traits, so it was expected that his DNA was related to this other human species extinct about 30,000 years ago in their last strongholds of the south of the Iberian Peninsula.
However, the DNA, the oldest read so far, shows an unmistakable kinship with Denisovans, whose only remains have been found thousands of kilometers from Spain.
"This study puts everything upside down," sums Martinez.
Scientists offer four possible scenarios to explain the surprise.
The first human who lived 400,000 years ago in Atapuerca had a common ancestor with Denisovans, and that common ancestor is not an ancestor of Neanderthals.
"Obviously means that Denisovans, whoever they are, were in the Middle Pleistocene occupying a vast geographical area, which was in Southeast Asia to western Europe," says geneticist Carles Lalueza-Fox, oblivious to this research and specialist ancient genomes.
According to this first option, a group of unknown until 2010, Denisovans, paced across Europe from end to end, even to the current Mongolia 400,000 years ago.
"A train of the Homo antecessor"
"I'm not so sure" says Martinez, Research Center on Human Evolution and Behavior of Madrid.
His team in this study, led by Svante Pääbo , also father of the genome of Neanderthals, raises a second possibility:
the population of the Sima is closely related to the ancestors of both neandertales as Denisovans.
"The Neanderthal mitochondrial DNA also be present [in humans from the Pit of Bones], but maybe in a group in another cave or other individuals of the same cave, we'll know in the future," says Matthias Meyer, Institute Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany).
"It's my favorite scene," says Meyer, lead author of the study, admitting that moment is just a 'speculation'.
Skeleton of one of the 'Homo heidelbergensis'
Sima of the Bones
Javier Trueba - Madrid Scientific Films
Another co-authors, paleoanthropologist José María Bermúdez de Castro , supports a third scenario:
the Homo antecessor , a human species 900,000 years also found in Atapuerca, one kilometer from the Sima de los Huesos, give their mitochondrial DNA Denisovans.
"Imagine a train that part of Homo antecessor , makes a stop at the Sima de los Huesos and reaches Denisovans" Bermudez de Castro, co - director of the Atapuerca and editorial advisor to explain matter .
"Where were the Neanderthals in this way? Well I do not know," he admits. "At the moment, I would not change the posters of the Museum of Human Evolution," he jokes.
His colleague Ignacio Martínez believes that obtaining such ancient DNA is a historic landmark, which opens,
"A new era in the study of human evolution."
However, he warns that DNA obtained from the two grams of femur Sima of the Bones is mitochondrial, which is inherited from the mother, so it is too early to make statements.
"If a Sioux Indian has a child with a Swedish woman, child mitochondrial DNA will tell us that comes from Sweden. This type of DNA shows only part of the story," he laments.
Atapuerca researchers are now working with experts from the Max Planck German to try to recover "at least a small part of the nuclear genome" of Homo heidelbergensis from Sima de los Huesos, according advances Matthias Meyer .
In the cell nucleus is the vast majority of the 25,000 genes of a human, but there are about 40 genes out of it, in the mitochondria, the power plants of the cells.
Mitochondrial DNA that humans inherit from their mothers is the one that has been recovered by the time the Homo heidelbergensis .
Neanderthals and Denisovans be a group with a common ancestor, while Sima human Bone be part of a different group.
This option is weak, because it would imply that Neanderthals traits in both groups emerged independently.
A year ago, researchers at Atapuerca announced that Homo heidelbergensis could talk about 400,000 years ago, after finding that the bandwidth of your ear canal was prepared to hear sounds emitted by current mouths.
Talk now expect their DNA ...
DNA Clarifies ...
Excavations at the
Sima de los Huesos at Atapuerca (Burgos).
JT / MSF
28 hominids that lie at the Sima de los Huesos
They had a close relationship with Neanderthals,
according to the first analysis of its nuclear genetic material
430,000 years ago, at least 28 children and adults of both sexes were killed and buried in a cave in the Sierra de Atapuerca, in Burgos.
When paleoanthropologists find them, they christened the site as the Sima de los Huesos, because from there they took over 6,700 human fossils.
It is still unclear whether it was a death trap or a grave with religious sense, but, over time, research on what happened there has become a global benchmark for the clarification of the least known chapters of human evolution.
Now, for the first time in the long history, it has been possible to analyze nuclear DNA from two individuals of the chasm. It is extracted genetic material from the cell nucleus, the oldest ever analyzed.
The simple fact of having managed to rescue him from a few micrograms of ground bone of a femur, several teeth and blades, is already a landmark achievement.
But the most interesting is the story reveals.
Atapuerca hominids
would archaic Neanderthals,
ancestors who inhabited Europe
and they passed sapiens.
The team of paleoanthropologists who heads excavations at Atapuerca believes that the 28 human buried there are archaic Neanderthals, ancestors of the modern members of this species that lived in Europe until about 40,000 years ago and with whom sapiens had sex and children.
The results showed an unexpected kinship with Denisovans, other hominids who lived in the remote Altai mountains of Siberia and whose discovery was announced in 2010.Ese relationship was narrower than the Neanderthals themselves. But this time the type of mitochondrial DNA was analyzed and therefore offered information only the maternal line.
The new analysis now provides the other half of the story, because the nuclear DNA carries information both lineage of the father and the mother.
Thus, DNA confirms that the Atapuerca hominids would archaic Neanderthals , ancestors of those who later conquered Europe and met with sapiens.
But the study also reaffirms that the mitochondrial DNA, the maternal line, is becoming related to their carriers with Denisovans.
Subsequent Neanderthals had a different mitochondrial DNA, although it is unclear why.
Sex everywhere
"The Sima de los Huesos is currently the only site without permafrost that allows us to study DNA sequences of the Middle Pleistocene, the previous 125,000 years period," notes Matthias Meyer, an expert in genetic sequencing of the Max Planck and first author of the study.
The work would not have been possible if paleoanthropologists who dug the pit had not taken exceptional measures to preserve bone and prevent them from being contaminated with DNA from other organisms.
"For many years we expect that advances in molecular analysis could one day help in the investigation of this unique fossil site in the world," said Juan Luis Arsuaga, co-director of Atapuerca and signer of the new study.
"So we drew some of the specimens with clean tools and have left encapsulated in the surrounding mud to minimize alterations after excavation" highlights.
Extracting DNA from the cell nucleus, ie cells that died 430,000 years ago, is a huge technological challenge, says Carles Lalueza-Fox , a researcher in ancient DNA expert who has not participated in this study.
The team started,
"With about 2,600 million sequences" of DNA and was ruling the vast majority to be left alone "with a few common positions" equivalent "to less than 1% of the human genome," he explains.
One of the conclusions drawn Lalueza-Fox of the material is the persistent occurrence of hybridizations, sex and fertile children between one species and another.
"We have half a dozen such data and found each hybridization" highlights.
Faced with this piece that does not fit, some of the study's authors speculate that perhaps due to a population of later Neanderthals would have come from Africa to Europe, he would have crossed with European groups and the DNA of the women would have ended up being dominant and diluting the remains provided by the Denisovans.
"These results give us important landmarks in the timeline of human evolution," said Svante Pääbo in a press release from the Max Planck.
The data "are consistent" with the hypothesis that separate us as a species sapiens other "archaic human" makes between 550,000 and 750,000 years highlights.
In addition, it is clear that Neanderthals and Denisovans divergence from a common ancestor ago happened before 430,000 years , the date of the Sima.
As usual, the analysis of ancient DNA gives another romp to the classic version of human evolution .
"On the one hand simplify the evolutionary history of these human and secondly the complicated," says José María Bermúdez de Castro, co-director of Atapuerca and one of the investigators.
In 2014, the team decided to withdraw from the chasm hominid classification as aspecies Homo heidelbergensis , explains.
Since then are in a kind of scientific limbo, assigned species, but with very clear morphological similarities neandertales, a connection confirming now DNA.
"The story we see now is very complicated, with a genealogy that Neanderthals had several branches, different lineages" occupying different areas and could reproduce with each other, explains.
Now,
"What remains to be determined is whether we have a species or a subspecies of Neanderthals in the pit," adds Bermudez de Castro.
The team believes that possibly more nuclear DNA can be extracted in the future, which would reveal new chapters of the still mysterious story surrounding the 28 bodies from the Pit of Bones.
One key is whether they were all members of one family.
"I honestly think that this evidence will be found," says Bermudez de Castro
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