Isotopic analyzes performed on single amino acids in Neanderthal collagen samples shed new light on their discussed diet

The Neanderthals' diet is the subject of much discussion: they are traditionally considered carnivores and hunters of large mammals, but this hypothesis has recently been questioned by numerous evidence of plant consumption. Ancient diets are often reconstituted with the help of nitrogen isotope ratios, a tracer of the trophic level, the position occupied by an organism in the food chain. Neanderthals apparently occupy a high position in terrestrial food chains, with ratios slightly higher than those of carnivores (such as hyenas, wolves or foxes) present at the same sites. It has been suggested that these slightly higher values ​​were due to the consumption of mammoth meat or putrid meat. And we also know examples of cannibalism for different Neanderthal sites.

Modern Paleolithic men, who arrived in France shortly after Neanderthals disappear, have even higher nitrogen isotope ratios than Neanderthals. This is classically interpreted as the signature of the consumption of freshwater fish. Fishing is supposed to be a typical modern human activity, but again, there is a debate about whether or not Neanderthals ate aquatic resources. When Klervia Jaouen, a researcher at the Max Planck Institute for Evolutionary Anthropology and the first author of the study, discovered high nitrogen isotope ratios in the collagen of two Neanderthals belonging to the human category. modern. regular consumption of fish.

The Neanderthals come from Cottés and the Cave of the Reindeer, in France, two sites where no fish remains were found. However, measurements were made on a dental root, which registers the four to eight year old diet of the individual's life, and on the bone of a baby's one. year. These high nitrogen isotope ratios could also indicate that Neanderthals were not weaned at this age, which is at odds with the case of the Neanderthal Les Cottés (the one whose root the tooth was analyzed), sign of early weaning of about one year. In other words, many explanations (consumption of freshwater fish, putrid meat, late weaning or even cannibalism) could explain such values ​​and identify the factor could change our understanding of the way of life Neanderthals.

Amino acid analysis

In order to explain these reports of exceptionally high nitrogen isotopes, Jaouen and his collaborators decided to use a new isotope technique. Compound-specific isotope analyzes (CSIA) enable the amino acids contained in collagen to be analyzed separately. Some of the isotopic compositions of amino acids are influenced by environmental factors and isotopic ratios of foods consumed. The isotopic ratios of the other amino acids are also influenced by the trophic level. The combination of these isotopic amino acid ratios makes it possible to decipher the contribution of the environment and the trophic level to the final isotopic composition of the collagen.

"Using this technique, we discovered that Neanderthal Cottés had a purely terrestrial carnivorous diet: it was neither a weaned child nor a regular fish eater, and its people seem to have mainly hunted reindeer and horses, "says Jaouen. "We also confirmed that the Neanderthal of the Reindeer Cave was a breastfed baby whose mother was a meat eater." Interestingly, this conclusion corresponds to the observations of zooarchaeologists.

The study also shows the importance of this new isotope technique for future research on ancient human and Neanderthal regimes. The use of compound-specific isotope analyzes has allowed researchers to misinterpret the overall isotope ratio of nitrogen, which was exceptionally high. Michael P. Richards, Simon Fraser University, Canada, commented: "Previous results for isotopes indicated a predominantly carnivorous diet for Neanderthals, consistent with the extensive archaeological inventory of animal remains found and deposited by humans. Neanderthals, with frank interpretations Data on bulk isotopes, ranging from Neanderthals living mainly to aquatic plants, eating one another, in stark contrast to archaeological evidence.These new compound-specific isotopic measurements confirm earlier Neanderthal interpretations as being composed mainly of large herbivores, also consumed other foods such as plants ".

Monotonous diet

In addition to confirming that Neanderthals are terrestrial carnivores, this work suggests that these hominins have followed a very monotonous diet over time, even when they began to alter their material industry, perhaps under Influence of the modern man. The Neanderthal baby from the Reindeer Grotto has indeed been associated with Chatelperronian, a lithic technology similar to that of modern humans. Late Neanderthals were therefore very human, painting caves and wearing necklaces, but unlike their sister species, they did not seem to like fishing.

Jean-Jacques Hublin, director of the Department of Human Evolution at the Max Planck Institute of Evolutionary Anthropology, comments: "This study confirms that Homo sapiens Arriving in Europe and meeting Neanderthals, they were in direct competition for the exploitation of large mammals. "The systematic use of the CSIA association and radiocarbon dating will help to understand whether the two species actually had the same subsistence strategies during these crucial periods. ", Concludes Sahra Talamo, researcher at the Max Planck Institute in Leipzig.

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