Fossil study finds vision—not the 'thinking' frontal lobe—drove varied brain development in primates
A new study led by a Duke University scientist overturns a long-held idea about how primates, including humans, came to have such large and sophisticated brains. The research finds that the dramatic expansion of the primate neocortex was driven largely by vision, not by the disproportionate growth of the frontal lobe often associated with higher reasoning.
A new study led by Richard F. Kay, a Duke University professor emeritus of Evolutionary Anthropology, challenges the belief that the frontal lobe is primarily responsible for the expansion of primate brains. Instead, the research suggests that the dramatic growth of the primate neocortex was driven by visual processing. The neocortex, the part of the brain responsible for sensory perception and complex cognition, expanded disproportionately in tarsiers and anthropoids, the group that includes monkeys, apes, and humans.
This expansion occurred along with an increase in the optic nerve, indicating heightened visual input. The study's findings, published in the journal Science, utilized high-resolution micro-CT scans and digital reconstructions of fossil skulls to create virtual endocasts, or models of the brain, enabling the comparison of brain volumes and surface areas across primate species.
The results reveal a consistent pattern of frontal lobe size growth as overall brain size increased, debunking the notion of an independent frontal lobe expansion. The research indicates that enhanced vision and associated adaptations, such as a retinal fovea and bony eye partition, have been an ancient feature of anthropoids for at least 33 million years.
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