A new research has revealed that an insect-rich diet when regular food sources were not available helped early humans develop bigger brains. The increase in size of the brains played a significant role in improving cognitive functioning.

The study from Washington University in St Louis showed that early humans found ways to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs that helped them develop bigger brains with higher-level cognitive skills.

Ancient humans must have started digging for insects during a period when the food was not easily available, which contributed to hominid cognitive evolution and made human beings to feel the need of advanced tool use, said Amanda D Melin, an assistant professor of anthropology in arts and sciences.

The study has supported the findings of an evolutionary theory that suggests the development of sensorimotor (SMI) skills, like increased manual dexterity, tool use and innovative problem solving, were the result of creative challenges to find insects and foods that are buried or embedded.

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

"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", said Melin.

The need to deal with the challenges of finding food have long been recognized to play an important role in shaping evolution of the brain and cognition in primates, including humans, said Melin.