Primate brain evolution lagged behind body size before overshooting, study finds

A new study revives the "brain lag" hypothesis, suggesting primate brain size lagged behind body size evolution before significantly overshooting. Researchers used molecular genetics to confirm that in some primate lineages, including humans, body size increased first, followed by brain size catching up and then exceeding expected levels. This evolutionary overshoot is linked to social group formation for predator defense and a shift to more energy-dense diets, though alternative theories exist.