Bug-eating helped early humans build bigger brains

An insect-rich diet when regular food sources were scarce was the secret behind early humans developing bigger brains with higher-level cognitive skills, new research reveals.

Figuring out how to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs may have spurred the development of bigger brains and higher-level cognitive functions in the ancestors of humans and other primates, suggests research from Washington University in St Louis.

"Digging for insects when food was scarce may have contributed to hominid cognitive evolution and set the stage for advanced tool use," said Amanda D Melin, an assistant professor of anthropology in arts and sciences.

The research provides support for an evolutionary theory that links the development of sensorimotor (SMI) skills such as increased manual dexterity, tool use and innovative problem solving to the creative challenges of foraging for insects and other foods that are buried or embedded.

The five-year study of capuchin monkeys in Costa Rica, published in the Journal of Human Evolution, is the first to provide detailed evidence from the field on how seasonal changes in food supplies influence the foraging patterns of wild capuchin monkeys.

"We find that capuchin monkeys eat embedded insects year-round but intensify their feeding seasonally, during the time that their preferred food - ripe fruit - is less abundant," Melin said.

This clearly suggests that embedded insects are an important fallback food.

Previous research has shown that fallback foods help shape the evolution of primate body forms, including the development of strong jaws, thick teeth and specialised digestive systems in primates whose fallback diets rely mainly on vegetation.

Modern humans frequently consume insects which are seasonally important when other animal foods are limited.

"This study suggests that the ingenuity required to survive on a diet of elusive insects has been a key factor in the development of uniquely human skills," Melin concluded.