For a long time, scientists thought that Neanderthals were large consumers of meat. Chemical analyzes of their remains seemed to indicate that they ate as much as high -level predators such as lions or hyenas. But in reality, the hominini-that is to say the Neanderthals, our species, and other close relatives today extinct-are not specialized carnivores. It is rather omnivores, which also consume many foods of vegetable origin.
It is possible for humans to survive with a very carnivorous diet. In fact, several groups of traditional northern hunters, such as the Inuit, were able to survive mainly thanks to foods of animal origin. But hominini simply cannot tolerate large amounts of protein such as large carnivores. In humans, prolonged excess of proteins without a sufficient quantity of other nutrients can cause protein poisoning – a debilitating, even mortal state, historically called “rabbit famine”.
So how can we explain the chemical signatures found in the bones of Neanderthals, who suggest that they ate a lot of meat without apparent problems?
I am an anthropologist and I study the food of our distant ancestors thanks to elements like nitrogen. New research that my colleagues and I conducted suggest that a secret ingredient in the Neanderthal regime could explain these chemical signatures: maggots.
Isotopic reports provide information on what an animal has eaten
The proportions of specific elements found in the bones of an animal allow you to have an overview of its diet. Isotopes are alternative forms of the same element, the mass of which differs slightly. Nitrogen has two stable isotopes: nitrogen-14 (the most common) and nitrogen-15 (heavier and rarer). We note their ratio in the form Δ15N, measured in “per thousand”.
As you get into the food chain, organizations have relatively more nitrogen-15 in them. Grass, for example, has a value of Δ15N very weak. A herbivore accumulates the nitrogen-15 that he consumes by eating grass, so that his own body has a value of Δ15N slightly higher. Carnivorous animals have the highest nitrogen ratio in a food network; The nitrogen-15 of their prey is concentrated in their bodies.
By analyzing the stable isotopic reports of nitrogen, we can rebuild the diets of the Neanderthals and the first Homo Sapiens during the end of the Pleistocene, which extended from 11,700 to 129,000 years before our era. Fossils from different sites tell the same story: these hominini have Δ values15N high. These values would place them typically at the top of the food chain, alongside hypercarnivores such as cave lions and hyenas, the diet of which is made up of more than 70% meat.
But maybe there was something else in their diet that inflates these values?
Discover the Neanderthal menu
Our suspicion was carried on the maggots, which could be a different source of nitrogen-15 enriched in the diet of Neanderthals. Asticots, which are flies of flies, can be a source of food rich in fats. They are inevitable after having killed another animal, easily collectable in large quantities and beneficial on the nutrition.
To explore this possibility, we used a set of data that had been initially created for a very different purpose: a medico-legal anthropology project focused on the way nitrogen could help estimate the time since death.
I initially collected contemporary samples of muscle tissue and asticots associated with the Center for Medico-Legal Anthropology of the University of Tennessee, in Knoxville, to understand how nitrogen values evolve during decomposition after death.
This decomposition food inevitably issued an intense stench that the first European explorers, the trappers and the missionaries were disgusted.
Although this data is thought of to help in current surveys on deaths, we have reused them to test a very different hypothesis. We have thus found that the values of the stable isotopes of the nitrogen increase modestly as muscle tissue decomposes, ranging from -0.6 per thousand to 7.7 per thousand.
This increase is more marked in the maggots themselves, who feed on this decomposing fabric: from 5.4 per thousand to 43.2 per thousand. To put these values in perspective, scientists believe that the values of Δ15N of herbivores of the Pleistocene vary between 0.9 per thousand and 11.2 per thousand. Measurements can be recorded for asticots that can be almost four times higher.
Our research suggests that the high values of Δ15N observed in the hominini of late Pleistocene could be swollen by consumption throughout the year of larval flies enriched in 15N found in dried, frozen or stored animal food.
Cultural practices influence food
In 2017, my colleague John Speth suggested that the high values of Δ15N among the Neanderthals were due to the consumption of putrefied or decaying meat, based on historical and cultural evidence of food regimes in hunters of the Arctic.
Traditionally, the indigenous peoples almost universally considered the food of animals entirely putrefied and infested with larval flies like highly sought -after dishes, not as survival rations. In fact, many people left regularly and, often intentionally, animal foods decompose to the point where they swarmed with larval flies and, in some cases, even began to liquefy.
This decomposition food inevitably issued an intense stench that the first European explorers, the trappers and the missionaries were disgusted. However, indigenous peoples considered these foods as good to eat, even as a delicacy. When asked how they could tolerate this foul smell, they simply replied: “We don’t eat the smell.”
How are the nutritional benefits of the consumption of larval flies change depending on the storage time for food?
Cultural practices of similar Neanderthals could well be the key to the enigma of their high values of Δ15N. The ancient hominini cut, stored, kept, cooked and cultivated a wide variety of products. All these practices enriched their paleolithic diet with foods in forms that non-hominini carnivores do not consume. Research shows that the values of Δ15N are higher for cooked foods, for putrefied muscle tissue from terrestrial and aquatic specimens and, according to our study, for the larvae of flies feeding on decomposition tissues.
High values of Δ15N of the asticots associated with putrefied animal foods help to explain how the Neanderthals have been able to include a wide variety of other nutrients beyond simple meat, while displaying values of Δ15N typical of those of hypercarnivores.
We suspect that the high values of Δ15N observed in Neanderthals reflect the regular consumption of fatty animal tissues and fermented stomach content, many being in the semi-Putrid or putrid state, as well as the inevitable bonus of living and dead larval flies enriched in 15N.
What is still unknown
Asticots are a resource rich in fats, dense in nutrients, ubiquitous and easily available, and both Neanderthals and the first Homo sapiens, as well as modern hunters, would have taken advantage of their full exploitation. But we cannot say that single larval flies explain why Neanderthals have such high values of Δ15N in their remains.
Several questions concerning this old diet remain unanswered. How many asticots was a person to consume to explain an increase in Δ values15N Beyond the expected values due to meat consumption alone? How are the nutritional benefits of the consumption of larval flies change depending on the storage time for food?
Additional experimental studies on variations in δ values15N processed, stored and cooked foods according to traditional indigenous practices could help us better understand the eating practices of our ancestors.
