Aquatic ape hypothesis

The conventional view of human evolution suggests that humans evolved on the savannah. The aquatic ape theory provides an alternative to this, suggesting a semi-aquatic setting.

The aquatic ape theory puts forward these main arguments:

Nakedness: Of the hundreds of primate species, humans are the only species in which hair does not cover almost the entire body. The only environments know to give rise to naked mammals are aquatic and subterranean. Other naked mammals are totally subterranean (naked mole rat), swimmers (whale, dolphin, walrus and manatee), wallowers (hippopotamus, pig and tapir) or seek mud and water regularly (rhinoceros and elephant).

Bipedalism: Humans are the only surviving bipedal mammal. Although it gives us the ability to use tools whilst walking or running, it directly causes the following problems: back problems, varicose veins, haemorrhoids, hernias and problems with childbirth. Since evolution works in small steps, it is hard to see how bipedalism could have evolved on the savannah: the mass of the torso makes bipedalism inherently unstable. Water, however, supports the body.

Breathing: With the exception of humans, land mammals, have no conscious control over their breathing. The voluntary control humans have over their respiratory system is similar to that of aquatic mammals which inhale as much air as they need for a dive, then return to the surface for air.

Fat: Humans have ten times as much fat in our bodies as is normal in an animal of our size. We are by far the fattest primates. Mammals which hibernate have seasonal fat: aquatic mammals, like humans, retain fat throughout the year.

Tears and excessive sweating provide further evidence to support the theory.

Alister Hardy originally suggested the theory. Elaine Morgan studied and promoted the theory, producing books on the subject including The Aquatic Ape and The Scars of Evolution.