Literature Review: Movement, Endurance, and the Sedentary Mismatch

The Running Ape

There is something strange about humans if you line us up against the rest of the animal kingdom. We are not fast. A house cat can outrun us. We cannot fly, we cannot swim particularly well, we have no claws, no venom, no armour. What we can do — better than any other animal on Earth — is keep going.

Daniel Lieberman and Dennis Bramble laid out the case in a landmark 2004 paper in Nature. The argument: humans did not evolve primarily as walkers. We evolved as runners. Specifically, as endurance runners — animals built to run long distances at moderate speeds in the heat, chasing prey until the prey collapsed from hyperthermia. This is the persistence hunting hypothesis.

The evidence is anatomical and it is persuasive. The human Achilles tendon stores and returns elastic energy during running but serves almost no function during walking. The nuchal ligament — a band of connective tissue running from the base of the skull to the spine — stabilises the head during running and exists in dogs and horses but not in chimpanzees. Our gluteus maximus, the largest muscle in the body, barely fires during walking but contracts powerfully during running. Our relatively long legs, short toes, and wide shoulders (decoupling the arm swing from the trunk) are all running adaptations. None of them make sense as walking adaptations.

But the most remarkable feature is our skin. Humans have between 2 and 4 million eccrine sweat glands distributed across the body surface. This is the highest density of any mammal. Most mammals cool themselves by panting — a method that is incompatible with sustained galloping because the respiratory cycle locks to the stride cycle. A horse running at full speed cannot pant independently of its gait. A human can sweat freely at any speed. This gives us an extraordinary thermoregulatory advantage. On a hot day, a human can m