Endurance running hypothesis

The endurance running hypothesis is a theory of human evolution according to which many features of human anatomy can be described as adaptations to long distance running.

Most researchers have focused on ER performance in modern humans, or on reconstructing ER performance in Homo erectus; one recent paper has discussed the hypothesis in relation to homo neanderthalensis. Recent research suggests that running economy (i.e., the energy cost of running at a given speed) is strongly related to the length of the Achilles tendon moment arm. It is supposed to have its origins in persistence hunting, when humans would chase after their prey over long distances until the animal overheated, allowing the hunter to kill it with a sharp object.

The hypothesis was first proposed by Carrier in 1984 and was refined in 2009 with a study of human toes, and has been gaining influence in the field of paleoanthropology.

Relationship to modern human characteristics
The hypothesis supposedly explains all of the following charactersistics in modern humans:


 * Hairlessness and an abundance of sweat glands, as a heat loss mechanism.
 * Ability to tolerate somewhat greater changes in body water content than many other animals (a marathon runner may sweat off 3% of their body mass during a race).
 * Short toes to allow gripping on soft surfaces, but not obstructing a good running stride.
 * Large gluteal muscles (a prime mover in running).
 * Human aptitude for endurance events such as ultra marathons; the Man vs. Horse Marathon in Wales has shown that given the right weather conditions, it is in fact possible for a human to outrun a horse over a distance of 22 miles (35km). Meanwhile, over a short distance, the average domestic cat could outrun Usain Bolt.
 * Increased body fat (1 pound of body fat is 3,500 kilocalories, which can be burned by the body to allow for greater distances covered at a time).
 * Long legs with springy tendons (long legs mean long stride, and springy tendons allows for a faster stride).
 * Intolerance of sedentary lifestyle, regarding and  pathologies.
 * Ability to breathe through the mouth while running (running experts advise inhaling through the nose and exhaling through the mouth to allow for maximum oxygen uptake without hyperventilating).

Criticisms
Archaeological evidence reveals that ungulates were the main prey of early man. Given their great speed, they would have easily been able to outrun early hominins. Ungulate speed, coupled with the variable visibility of the savanna-woodland, meant that hunting by endurance running required the ability to track prey, which would have been difficult given the lack of penetrating projectile technology at the time.

Persistence hunting is also a very costly way to hunt. It's been argued that the energy expenditure of chasing animals to death was simply too high relative to energy gotten back from killed prey, particularly if one presumes prey may occasionally escape, resulting in a high energy expenditure with no food returned.

A weaker argument against is the claim that persistence hunting could not have been utilized as a primary form of hunting for too long because eventually prey would be expected to evolve instinctual understanding of what humans were doing and evolve countermeasures to it. For example, prey subject to persistence hunting long enough might start grouping up with the herd to defend against or attack would-be persistence hunters instead if fleeing. This is generally considered a weaker argument, because while it is true that prey species would likely eventually evolve better defenses against persistence hunting, it's still possible that humans utilized the technique but did not rely on it long enough for prey to have had time to evolve counter tactics to it before before humans had developed better tools and alternative hunting methods.