Cranial Capacity Decline in the Holocene

Holocene Humans

The archaeological data indicate that cranial capacity relative to body size has decreased worldwide from Pleistocene Australians to Archaic Africans. Here I will argue that differences in movement, climate, and diet explain the difference between Holocene and Pleistocene H. Sapiens.

This paper reconstructs the relative proportions of archaic brains. NT = Neandertal, EH = Pleistocene human, MH = Holocene human. One thing that is immediately obvious is the decrease in the visual cortex size in Holocene humans. What is the cause of this? Is it environmental or genetic?

The link between physical activity, gray matter, and brain size has been identified by numerous papers (Gray and white matter correlates of navigational ability in humans, ScienceDirect, Physical Exercise Habits Correlate with Gray Matter Volume of the Hippocampus in Healthy Adult Humans — Dimensions). A further review confirms that 82% of gray matter in the brain is directly modifiable by physical movement. Molecular evidence in the form of physical-activity induced BDNF (Brain-derived neurotrophicfactor) supports the idea that the brain grows from physical activity (Exercise promotes the expression of brain derived neurotrophic factor (BDNF) through the action of the ketone body β-hydroxybutyrate) . Thus the ontogeny of the brain is crucially linked the the type, frequency, and conditions of physical movement.