In recent years, human population growth, coupled with the climate crisis, environmental pressures, and current production and consumption patterns, has driven the search for alternative food sources. With 1,611 insect species listed as edible, organizations such as the Food and Agriculture Organization of the United Nations (FAO) have proposed insects as a sustainable food source. However, despite the fact that hundreds of millions of people already consume them, Western societies continue to show aversion to entomophagy. While this rejection may have a cultural basis, its origin remains unknown.
To explore its roots, a study by the Institute of Evolutionary Biology (IBE) , a joint centre of the Spanish National Research Council (CSIC) and Pompeu Fabra University (UPF) , has used genomic analyses to reconstruct insect consumption over the past thousands of years. The research, published in Science Advances, suggests that insect consumption was sporadic and accidental in Europe, Central and East Asia, while it would have been more frequent in tropical regions and among Neanderthal populations. The results shed light on human evolution, ecology, and current insect consumption.
Genomic analysis reconstructs the history of entomophagy in Eurasia
To find evidence of insect consumption, the IBE team analyzed 745 samples of dental calculus (tartar) from anatomically modern humans, dating back up to 33,000 years. Tartar preserves traces of DNA from the species regularly consumed in the diet. The dental analyses suggest that modern humans in northern Eurasia did not routinely practice entomophagy. The team also studied the human genes involved in the digestion of chitin, a component of the insect exoskeleton. In North Eurasian human populations, chitinase genes carry mutations that confer a reduced capacity to digest insect exoskeletons, a trait that has persisted for the last 9,000 years, since the advent of agriculture.
"The scarce presence of insects in the diet of northern Eurasians suggests that the absence of entomophagy is not solely due to recent cultural factors, but also to a long ecological and evolutionary history", says Pablo Librado, principal investigator at the IBE who led the study.
Neanderthals may have consumed insects more frequently
Despite inhabiting the same environment, Neanderthals had a greater abundance of insect DNA in their dental calculus than anatomically modern humans. These levels in Neanderthals are comparable to those found in western chimpanzees, which rely on entomophagy to supplement their diet on the savanna, especially during periods of drought.
The most abundant DNA remains in Neanderthal tartar belong to Diptera, the insect group that includes flies and mosquitoes, with the latter being particularly prominent. These findings support a recent hypothesis about the regular consumption of animal carcasses infested with fly larvae. The abundance of mosquito remains reinforces the possibility that the carcasses of their prey were kept in ponds and marshy areas, where mosquitoes lay their eggs.
The study also revealed that Neanderthal chitinase genes facilitate better digestion of insects, as also observed in the only Denisovan specimen analyzed.
The genetic imprint of entomophagy persists in tropical populations
The team analyzed genes linked to the digestion of insect exoskeleton chitin. These genes are expressed in the stomach and encode the enzymes chitinase acid (CHIA) and chitobiase (CTBS). In both ancient and modern samples, the researchers identified genetic variants associated with a greater expression of these enzymes in populations inhabiting areas near the tropics.
"Large quantities of insects need to be ingested to compensate for the high caloric expenditure involved in their collection. In the tropics, there is a greater availability of social insects, such as termites and locusts: their biomass and diversity allow for sustainable exploitation throughout the year, which even contributes to pest control", explains Manuel Piñero, a predoctoral researcher at the IBE and first author of the study.
The expression of these enzymes gradually decreased as populations moved towards higher latitudes. This latitudinal genetic variation, maintained for at least 9,000 years, reflects the abandonment of entomophagy in European populations.
The future of entomophagy in Europe
"Beyond cultural or religious factors, our results suggest that the reduced availability of insects in non-tropical areas may have been a key factor in the abandonment of entomophagy, leading to a reduced capacity to digest insect exoskeletons", Librado comments.
However, modern industrial processing allows us to take advantage of the nutritional properties of the food source without needing to digest this component, in addition to allowing its mass production in edible insect farms.
The Ancient Population Genomics research group led by Pablo Librado at the IBE studies the domestication process, using insect species recently approved for human consumption as a model and by comparing the genomes of farmed insects with the genomes of pre-domestication individuals extracted from entomological collections. "We investigate the evolution of domestication in animals, which also gives us information to improve the exploitation of insects for consumption, both as animal feed and for human consumption", Librado concludes.
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