How Exercise Made Humanity Smarter

What’s the Latest Development?

Relative to other mammals, the size of the human brain is about three times larger than would be expected, given our body mass. A new theory is emerging which suggests that exercise may be to thank for that. Similar to humans, mammals like dogs and rats have a high physical endurance rate and also have large brain sizes relative to their bodies. In laboratory experiments, scientists have found that animals which exercise the most create offspring, over several generations, rich in body chemicals that promote tissue growth and health. 

What’s the Big Idea?

Among the chemicals found in more active animals is a protein called brain-derived neurotrophic factor, or BDNF, which is known to assist endurance performance and drive brain growth. As our more athletic ancestors were able to catch more food, their genes had a higher probability of being passed down. “Eventually, these early athletes had enough BDNF coursing through their bodies that some could migrate from the muscles to the brain, where it nudged the growth of brain tissue.” The larger point is that if physical activity shaped our contemporary brain, exercise should help maintain its robustness.

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