For paleontologists, the remains that appear in the deposits can be authentic windows into the past. From the DNA of the bone remains, for example, it is possible to know everything from diseases to the eating habits of the animals to which they belonged. The same is true of the spoils of our evolutionary ancestors and cousins, such as Neanderthals or Denisovans. Well, an international team of researchers, including scientists from the University of Oviedo and the Higher Council for Scientific Research, Pompeu Fabra University and the National Museum of Natural Sciences (MNCN), has developed a technique that allows to study the practices of hominid groups based on the DNA present in the sediments that make up the strata of caves or other archaeological deposits – in the ground it is possible to find traces of faeces, blood or decomposed organisms – even in those in the no bones have appeared.
In an article published in the journal Science , the study authors explain that to carry it out they analyzed 85 sediment samples from between 550,000 and 14,000 years ago, from eight enclaves in Europe and Asia, including the El Sidrón cave, in Asturias. Until now, the absence of fossils had been hindering the work of scientists, since it made it impossible to know with certainty which species had inhabited a certain place. But this advance, which is based on the analysis of fragments of mitochondrial DNA – this is inherited through the mother and is very useful for studying lineages – could change everything. “This work represents an exceptional advance because it allows us to know what species of hominid occupied a cave or a specific stratigraphic level, even in the absence of any remaining bones or skeletons. The novelty is to take advantage of what was discarded until now, the soil sediment, and discovering that it is full of DNA sequences from organisms that occupied that terrain “, Antonio Rosas, from the MNCN, points out in a statement.
This strategy has revealed, for example, what level of the land occupied the Neanderthals and Denisovans in the Denisova site, in Siberia, solely from the DNA present in it, and thus determine that the latter occupied the oldest stratum and that both species alternated in the cave. In El Sidrón, where numerous remains of Neanderthals who lived about 49,000 years ago have been recovered, a mitochondrial genome appeared that does not correspond to those that were already known .
“We know that some components of sediments can bind to DNA, so we decided to investigate whether that of ancient hominids could survive in the sediments of the archaeological sites they occupied,” Matthias Meyer, one of the coauthors of this work, from the Max Planck Institute for Evolutionary Anthropology. “The origin of the recovered DNA seems to come from depositions made in situ or from the decomposition of the bodies in the caves”, details the geneticist of the CSIC Carles Lalueza-Fox, one of the world’s leading experts in this field, who has also participated in this initiative.
Image: Joan Costa / CSIC
