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In 1994, during the excavations directed by Juan Luis Arsuaga, José María Bermúdez de Castro and Eudald Carbonell, more than 170 human fossils at stratigraphic level TD6 of the site of the in the Gran Dolina.
From these remains, three years later the new species, theHomo antecessor.
Now, the analysis of one of the molars found then, from 800,000 years old, sheds light on one of the most interesting points of thehuman genealogy, achieving an antiquity much higher than that which had been achieved to date by obtaining DNA.
The finding has been possible thanks to the multidisciplinary collaboration between scientists from the University of Copenhagen (Denmark), the National Center for Research on Human Evolution (CENIEH-ICTS), the Center for Genomic Regulation (CRG), the Pompeu Fabra University, the UCM-ISCIII Joint Center for Human Evolution and Behavior, the Catalan Institute of Human Paleoecology and Social Evolution (IPHES) and the Complutense University, among others.
Ancient protein analysis, published in the journalNature, provides evidence of aclose relationship betweenHomo antecessor, Homo sapiens, Homo neanderthalensis and the denisovans.
“Our results support the idea thatHomo antecessor was abrother group of the set of hominids that form Neanderthals, modern humans and Denisovans, so we must assume that the phylogenetic trees that we have obtained describe well the kinship relationships between these groups of hominids ”, he points out.Frido welker, researcher at the Globe Institute of the University of Copenhagen and first author of the article.
Rebuilding the human family tree
By using a technique calledmass spectrometry, the researchers they sequenced ancient proteins of the tooth enamel, and were able to determine very precisely the position ofHomo antecessor in the human family tree.
The new method, developed by researchers at the Danish university's Faculty of Medical and Health Sciences, allows scientists retrieve molecular evidence for accurately reconstruct human evolution from times that had not yet been accessed.
The respective genealogies of chimpanzees and humans diverged between seven and nine million years ago.
Since this data is available, scientists have worked to better understand the evolutionary relationships between modern humans and all the other species of our lineage, of which only their fossil remains remain.
“Much of what we know so far is based on the results of ancient DNA analysis or observations of the physical shape and structure of fossils. Due to the chemical degradation of DNA over time, the oldest human genetic material recovered to date barely exceeds 400,000 years ”, explains Enrico Cappellini, associate professor at the Globe Institute and main leader of the research group.
Now, the analysis of ancient proteins with mass spectrometry, an approach commonly known aspaleoproteomics, allows us to overcome these limits ”, adds Cappellini.
Theories about human evolution
When the fossils ofH. predecessor were discovered in 1994 and the proposed species in 1997, initial observations led to the conclusion that This hominid had been the last common ancestor of Neanderthals and modern humans, a conclusion based on the morphology of the fossils.
For years, the exact relationship betweenHomo antecessor and other human groups, such as sapiens and Neanderthals, has been intensively discussed among experts.
“The Atapuerca researchers opened a huge scientific debate on the role ofHomo antecessor and now we have closed it from where you could not dream of at that time, from the paleoproteomics. We hope that the same technique will close many more debates in the future ”, he adds.Carles Lalueza-Fox, principal investigator at the Institute of Evolutionary Biology (IBE-UPF) and co-author of the article.
Although the hypothesis thatHomo antecessor as a common ancestor of Neanderthals and modern humans it is very difficult to fit into the evolutionary stage of the genusHomo, the new findings in TD6 and subsequent studies revealed severalshared characters between Neanderthals and human species found in Atapuerca.
Furthermore, additional studies confirmed that the facial characteristics ofHomo antecessor are very similar to those ofHomo sapiens and very different from those of Neanderthals and their more recent ancestors.
“I am glad that the protein study provides evidence on the possible relationship betweenHomo antecessor, the common ancestor of Neanderthals, modern humans, and Denisovans. The characteristics shared by the TD6 species with these hominins appeared clearly much earlier than previously thought. Therefore, it could be a basal species of emerging humanity that gave rise to Neanderthals, Denisovans and modern humans ”, he declaresJosé María Bermúdez de Castro, from CENIEH and co-author of the work.
The study of human evolution by paleoproteomics will continue in the coming years through the recently started projectPalaeoproteomics to Unleash Studies on Human History (PUSHH), funded by the European Union and to which many of the article's co-authors belong. "I'm really looking forward to seeing what paleoproteomics will reveal in the future," says Cappellini.
In this senseMaria Martinon, Director of CENIEH and co-author of the research concludes: “It is exciting to be pioneers in the application of such an innovative field as that of paleoproteomics to the human fossil record. The next few years will be full of scientific surprises ”.
Frido Welker et al. "The dental proteome ofHomo ancestor” Nature April 1, 2020.