Long Distance Running Might Be Why Human Brains Are Big

Endurance exercise across generations could be responsible for our giant human brains and our success as a species. Take a look at the research that says running might have made our brains big.

Rigorous endurance exercise across generations could have been responsible for the success of humans as a species, says a recent scientific study. Our most notable physical trait as humans is our large brains. We are distinctly abnormal in the animal world, with brains about three times the size predicted by the size of the human body. Aside from requiring larger hats, larger brains usually spell success for animals. How did we develop large brains? Science says that aerobic exercise may have contributed.

The study examined the athletic prowess and brain size of many different mammals from gazelles to mice to humans. The primary measures examined were maximum metabolic rate and VO2 max. Researchers found that the longer and harder the animal could run, the larger its brain. The correlation was very significant, meaning there is definitely some interplay between exercise and brain size – at least in non-human animals.

But when they threw in the human data, it messed up the nice, neat trend that had emerged. Human brains are so incredibly large compared to our bodies that endurance ability alone can’t explain it. So what is the other cause? Well, nobody knows for sure, but some think increased protein consumption during evolution played a part. The development of group hunting tactics and increased availability of protein may be responsible for the huge advances in human evolution starting two million years ago. However, after the Agricultural Revolution humans stopped this rapid growth and started shrinking, both in brain and overall body size.2

A few people have gone as far as to theorize that it was the incredible endurance ability of primitive humans that allowed them to become such proficient hunters.3 Perhaps primitive humans used their superior cooling system (sweat) to track down and exhaust their prey? This is a very cool theory, but it’s still mostly speculation. I’ve seen more than one author try to pass it off as fact, but the evidence just doesn’t exist yet.

While exercise was once thought a leisure activity, evidence is mounting that it is hardcoded into our DNA. If exercise really played a pivotal role in the development of our genetic identity as humans, then this is no surprise.


1. David A. Raichlen and Adam D. Gordon. Relationship between Exercise Capacity and Brain Size in Mammals. PLoS One. 2011; 6(6). Published online June 22, 2011. doi: 10.1371/journal.pone.0020601

2. Clark Spencer Larsen. Animal Source Foods and Human Health during Evolution. The Journal of Nutrition vol. 133 no. 11 38935-38975.

3. DM Bramble and DE Lieberman. Endurance running and the evolution of Homo. Nature 2004 Nov 18; 432(7015):345-352.

Photo courtesy of Shutterstock.