A discovery in the Cantabrian cave of El Castillo further narrows the gap between Neanderthals and our species.

The discovery of six small flint knives in the Cantabrian cave of El Castillo, in Puente Viesgo, one of the most important in the world for the study of the Middle and Upper Paleolithic, concludes that the Neanderthal population that lived in the cave between 45,000 and 70,000 years ago had contact with other human groups located as far away as 420 kilometers, in the French region of Les Landes, which is the longest distance proven to date in exchanges of this group of hominids in Europe and Asia.

The discovery, according to all the scientists who participated in the study and other experts, is another milestone in the current trend of considering Neanderthals - who lived in Europe and Asia between 40,000 and 300,000 years ago - much closer to our species, Sapiens , in their behavior and technological and social skills than was assumed just a decade ago.

The study, led last year by José Manuel Maíllo and Juan Marín, professors of Prehistory at UNED, and published in the Journal of Human Evolution , one of the most prestigious international Anthropology journals, has revealed not only the existence in El Castillo of the half dozen pieces originally from Tercis (France), but also of dozens more that traveled from flint deposits in central Asturias and Treviño, in the Ebro basin, resulting in a wide mobility zone for Neanderthals of about 600 kilometers from east to west and about 150 kilometers in a southerly direction.

According to Maíllo, "The conclusion of this work is yet another contribution to the idea that Neanderthals had a much larger social territory than previously thought, when their range was presumed to be about 50 kilometers. Exchanges between groups separated by up to 200 kilometers were subsequently demonstrated in areas of Italy and Armenia, but the confirmation of the presence of the extremely high-quality flint from Tercis at El Castillo doubles the magnitudes we knew."

Álvaro Arrizabalaga, professor of Prehistory at the University of the Basque Country, emphasizes that "it is a very important discovery within this trend that brings the behavior, not only technological but also social, of Neanderthals closer to our species, at a key site on the Peninsula such as the El Castillo cave."

“The general framework is very different from ten years ago, when the paradigm greatly differentiated the two species in behavior and on a physical level; the distances between them were maximized. Since 2016, when the entire human genome was sequenced, it was discovered that we share DNA with Neanderthals, that we are hybrids in that sense,” Arrizabalaga continues.

The identification of the origin of the flint tools from the Tercis site was possible thanks to the geological study of globigerinoids, marine microfossils, led by Diego Herrero, a researcher at the University of Vigo.

The 262 pieces found in the cave come from an excavation directed by archaeologists Victoria Cabrera and Federico Bernaldo de Quirós between 1980 and 2003, although, according to Maíllo, "the majority have not been identified due to alterations inherent to the raw material, since the flint loses its silica due to contact with water laden with calcium carbonate, so abundant in the caves."

The tools were dated using carbon-14 and electron spin resonance (ESR) methods, which analysed isotopes in the dentin (the intermediate tissue of a tooth) of animal remains found in the same archaeological levels as the pieces. Two of these remains are estimated to be around 70,000 years old, while the rest are estimated to be around 47,000 years old.

According to Roberto Ontañón, director of the Caves of Cantabria and the Museum of Prehistory and Archaeology in this region, "The more we understand Neanderthals, the more they resemble us. Until now, it was assumed that they had resource-gathering areas in small territories and in isolated groups, which has been suggested as one of the causes of their extinction. However, the emergence of new findings forces us to reconsider and warns us about the complexity of their behaviors and social skills."

Thus, according to this researcher, the gradual exchanges of neighbors with neighbors, leading to contact with population groups in France, are something demonstrated in the Magdalenian period, the people who lived in Altamira 15,000 years ago, with their long-range exchanges. "Recent discoveries about Neanderthal mobility, and especially those obtained at El Castillo, equate these patterns with our own," Ontañón concludes.

Álvaro Arrizabalaga also highlights that among the raw materials of the pieces found there are several from the Ebro basin. “Until 2000 it was interpreted that the westernmost Cantabrian region was like a dead end , that the prehistoric populations were related only towards the north towards France - in the caves of the Basque Country, however, flint from Treviño has been found - and these discoveries reveal a collapse of the theory, because the mountains to the south are not excessively high and logically were not insurmountable”.

According to this professor at the University of the Basque Country, "this exchange or mobility explains much better the settlement of the Iberian Peninsula and is confirmed by the sites that are appearing in the Ebro basin itself and even on the plateau: in the Madrid region, three sites from the Aurignacian period (about 40,000 years ago) were discovered last year, one even on a plot of land next to the Delicias station, right in the city center!"