Ancient teeth and human DNA are revealing a surprising history of insect eating. While modern humans in northern Eurasia appear to have eaten insects only occasionally, Neanderthals may have consumed them more regularly. Populations near the tropics also retained genes that make insect exoskeletons easier to digest. Researchers from the Institute of Evolutionary Biology (IBE), a joint center of the Spanish National Research Council (CSIC) and Pompeu Fabra University (UPF), have used genomic evidence to reconstruct patterns of insect consumption stretching back thousands of years. Their findings, published in Science Advances, suggest that eating insects was likely occasional and accidental in Europe, Central, and East Asia, while it appears to have been more common in tropical regions and among Neanderthals. Ancient teeth examined by the IBE researchers suggest that modern humans living in northern Eurasia did not regularly eat insects. The team also studied genes involved in breaking down chitin, a major component of insect exoskeletons. Among North Eurasian populations, chitinase genes contain mutations associated with a reduced ability to digest insect exoskeletons. This genetic pattern has persisted for about 9,000 years, dating back to the rise of agriculture. The situation was different for Neanderthals. Although they lived in many of the same environments as anatomically modern humans, their dental calculus contained considerably more insect DNA. The amount detected in Neanderthal samples was similar to levels found in western chimpanzees, which use insects to supplement their diets on the savanna, especially during droughts. Among the most common genetic traces in Neanderthal tartar were remains from Diptera, the insect group that includes flies and mosquitoes. Mosquito DNA was especially abundant. These findings support the idea that Neanderthals may have regularly eaten animal carcasses containing fly larvae. The strong presence of mosquito remains also suggests that prey carcasses may have been stored in ponds or marshy environments, where mosquitoes would have laid their eggs. Genetic evidence further supports this idea. Neanderthal chitinase genes appear to have supported more efficient insect digestion, a pattern also seen in the only Denisovan specimen included in the analysis. The researchers also studied genes involved in digesting chitin found in insect exoskeletons. These genes are active in the stomach and produce enzymes such as chitinase acid (CHIA) and chitobiase (CTBS). Across both ancient and modern samples, populations living closer to tropical regions were more likely to carry genetic variants associated with higher expression of these enzymes. In the tropics, there is a greater availability of social insects, such as termites and locusts, whose biomass and diversity allow for sustainable exploitation throughout the year. As human populations expanded toward higher latitudes, the expression of these digestive enzymes gradually declined. This geographic pattern has remained in place for at least 9,000 years and appears to reflect the gradual abandonment of insect eating among European populations. The findings suggest that Western reluctance to eat insects may have roots that extend far beyond recent customs or religious traditions. Beyond cultural or religious factors, 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. Modern food production changes this equation. Industrial processing can make it possible to use the nutritional benefits of insects without requiring people to directly digest as much of the chitin in their exoskeletons. Insect farming also makes large-scale production possible. The Ancient Population Genomics research group led by Pablo Librado at the IBE is now studying how insect domestication develops. Researchers are using species recently approved for human consumption as models and comparing the genomes of farmed insects with those of pre-domestication individuals preserved in entomological collections. This research into the evolution of domestication in animals also provides information to improve the exploitation of insects for consumption, both as animal feed and for human consumption.