Human evolution

Human evolution in the bioenergetic framework centers on the brain's exceptional glucose demand: at roughly 2% of adult body weight, the human brain consumes about 20% of resting metabolic rate in adults and 66% in a 5-year-old, fueled primarily by glucose rather than fat or protein.

I think fruit eating is a good candidate for supporting evolution to be more human than ape-like, supporting a big brain and the kind of digestive system we have.

— Ray Peat

The "meat made us human" hypothesis, revisited

The dominant narrative in paleoanthropology has long credited meat-eating, not carbohydrate, as the key driver of hominin brain expansion. A 2026 computational model spanning roughly 4 million years of hominin evolution challenges that framing directly: it estimates early hominins such as Australopithecus afarensis derived more than two-thirds of dietary energy from naturally occurring sugars, chiefly fruit and honey, with protein contributing less than 20% of dietary energy across the full span modeled. Fruit and honey sugars, followed by cooked starchy tubers once cooking became available, were positioned to meet the rising glucose demand of enlarging hominin brains and reproduction, since raw starch does not readily release glucose. The authors propose animal foods and carbohydrate-rich plant foods played complementary roles rather than meat alone driving the process, and that glucose's role has been underestimated in the field.

Supporting physical evidence cited alongside the model includes tooth and jaw morphology, color vision adapted to spotting ripe fruit, dental caries patterns, and stable isotope ratios in fossil remains, together suggesting a diet high in sugars across early hominin evolution, alongside modern human traits (sweet taste receptors, smaller teeth/jaw/gut, and glucose-metabolism genetic variants) consistent with dietary selection pressure from carbohydrate intake.

See also

• Fruit
• Sugar
• Brain
• Glucose
• Bioenergetics