As the planet heats up and the population balloons, researchers and policymakers are getting increasingly desperate about where our next meal is coming from. One humble suggestion: bugs. Yes, insects - a mere 1,611 species of which are officially classified as edible, and which the Food and Agriculture Organization of the United Nations (FAO) has been pushing as a sustainable food source.

But Western societies, in particular, remain stubbornly unenthusiastic about entomophagy - the fancy term for eating insects - even as hundreds of millions of people worldwide happily munch on them. Culture might explain some of this distaste, but scientists had no idea how deep the aversion runs or what else might be behind it.

Enter researchers from the Institute of Evolutionary Biology (IBE), a joint venture of the Spanish National Research Council (CSIC) and Pompeu Fabra University (UPF). They've used genomic evidence to reconstruct insect-eating patterns stretching back millennia. Their findings, published in Science Advances, suggest that our ancestors in Europe, Central and East Asia probably ate insects only occasionally - and often accidentally - while tropical folks and Neanderthals were far more keen. The study offers fresh insights into human evolution, ecology, and why we still turn up our noses at a perfectly good cricket.

**Ancient Teeth Spill the Beans (and Bugs)**

The IBE team examined 745 samples of dental calculus (tartar) from anatomically modern humans, dating back up to 33,000 years. Tartar is a great repository of DNA from foods regularly eaten, giving researchers a dietary record straight from the source. The results indicate that modern humans in northern Eurasia didn't regularly eat insects. Additionally, the team looked at genes involved in breaking down chitin - the tough stuff in insect exoskeletons. North Eurasian populations carry chitinase gene mutations linked to a reduced ability to digest those shells, a pattern that has held steady for about 9,000 years, coinciding with the dawn 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: Surprisingly Adventurous Eaters**

Neanderthals, on the other hand, were apparently less picky. Their dental calculus contained significantly more insect DNA, even though they lived in similar environments. The insect DNA levels were comparable to those found in western chimpanzees, which supplement their diets with insects on the savanna, especially during droughts.

Among the most common genetic traces in Neanderthal tartar were from Diptera - the insect group that includes flies and mosquitoes. Mosquito DNA was especially abundant. This supports a recent hypothesis that Neanderthals may have regularly eaten animal carcasses containing fly larvae. The strong presence of mosquito remains also hints that prey carcasses might have been stored in ponds or marshy areas, where mosquitoes would happily lay eggs.

Genetics backs this up: Neanderthal chitinase genes appear to have supported more efficient insect digestion, a pattern also seen in the only Denisovan specimen analyzed.

**Tropical Populations Kept Their Insect-Digesting Genes**

The researchers also looked at genes involved in digesting chitin, specifically those producing the enzymes chitinase acid (CHIA) and chitobiase (CTBS). Across ancient and modern samples, populations nearer the tropics were more likely to carry genetic variants linked to higher enzyme expression.

"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.

As populations moved to higher latitudes, expression of these digestive enzymes gradually declined. This geographic pattern has persisted for at least 9,000 years and likely reflects the gradual abandonment of insect eating among European populations.

The findings suggest that Western reluctance to eat insects may have roots far deeper than recent customs or religious traditions. "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.

In other words, ecology helped shape both our diets and our biology. Where insects were scarce and not worth the effort, they simply became less appealing over time.

But modern food production changes the game. Industrial processing can make insects nutritious without requiring us to directly digest all that chitin. Insect farming also allows for large-scale production.

The Ancient Population Genomics research group led by Pablo Librado at the IBE is now studying how insect domestication develops. They're using species recently approved for human consumption as models and comparing the genomes of farmed insects with pre-domestication individuals preserved in 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.

So the next time you recoil at a bug on your plate, remember: it's not just you, it's 9,000 years of evolution. And also, those Neanderthals were way ahead of the curve.

Materials provided by Spanish National Research Council (CSIC). Note: Content may be edited for style and length.

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