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New research suggests that the reason Neanderthal remains have high nitrogen levels is due to them eating maggots, challenging theories that the ancient humans ate as much fatty meat as hypercarnivores like lions and wolves.
Neanderthal remains have high stable nitrogen isotope ratios (δ15N), similar to or even higher than the levels seen in large carnivores from the same sites. The ratio between nitrogen-14 and nitrogen-15 is a rough guide to the location of an organism on the food web. Nitrogen-15 accumulates in animals which eat other animals. Higher relative levels of nitrogen-15, therefore, suggests an animal which is higher on the food web.
Previous studies suggested that high nitrogen isotope ratios in Neanderthals were present because the hominins were hypercarnivores.
In fact, anatomically modern humans from the Late Pleistocene (129,000 to 11,700 years ago) also have high nitrogen levels. This has been seen as evidence that early modern humans, like Neanderthals, were consuming a large amount of animal foods as well as freshwater fish and seafood.
The new study, published in Science Advances, challenges this theory.
“The view that Neanderthals had diets like hypercarnivores (i.e., predators such as felids, hyenas, African hunting dogs, and wolves) has not gone without challenge,” the authors write. “Some scholars have suggested other explanations for the high δ15N values, such as the consumption of starchy plant foods, mushrooms, aquatic resources, putrid meat, and/or cooking.”
“While it is possible for humans to subsist on a very ‘carnivorous’ diet, many traditional northern hunter-gatherers such as the Inuit subsisted mostly on animal foods, hominins simply cannot tolerate the high levels of protein consumption that large predators can,” says corresponding author Melanie Beasley from Purdue University in the US.
Beasley’s team suggests another source which is extremely high in nitrogen: maggots.
They say that ethnographic studies have shown that Indigenous cultures around the world have historically consumed putrefied food stuffed with larvae for extra nutrients.
Perhaps Neanderthals did as well.
The team performed stable nitrogen isotope ratio analyses on 389 larvae from 3 fly families (Calliphoridae, Piophilidae, and Stratiomyidae). The larvae were gathered from the flesh of people who had donated their bodies to putrefy after death in a forensic anthropology laboratory.
Putrefaction alone leads to an average increase of the δ15N value of about 1 part per thousand. Putrefied flesh had δ15N values from –0.6 to 7.7 parts per thousand (where a negative value indicates less nitrogen-15 than the atmospheric standard).
On the other hand, δ15N values of the maggots ranged from 5.4 to 43.2 parts per thousand.
Beasley and colleagues say that these values could mean: “It is the maggots, more so than the carcass tissues themselves, that gave Late Pleistocene hominins both a rich source of fat and a very highly nitrogen-15-enriched source of protein.”
They suggest that “humans, Neanderthals included, are primates, not hypercarnivores, with very different digestive and metabolic systems, such that the normal daily protein intakes of the large predators, if consumed by hominins on a sustained basis, would be toxic, even lethal.”