Aquatic ape hypothesis

The aquatic ape hypothesis (AAH), also referred to as aquatic ape theory (AAT) and more recently the waterside model, is the idea that the ancestors of modern humans were more aquatic in the past. The hypothesis in its present form was proposed by the marine biologist Alister Hardy in 1960 who argued that a branch of apes was forced by competition from life in the trees to hunt for food such as shellfish on the sea shore and that this explained many characteristics such as man's upright posture. This proposal was noticed by Elaine Morgan, a scriptwriter, who objected to the male image of the "mighty hunter" being presented in popular anthropological works by Raymond Dart, Desmond Morris and others. While her 1972 book The Descent of Woman was very popular with the public, it attracted no attention from scientists, who saw no way of testing assertions about soft body parts and human habits in the distant past.

Morgan removed the feminist polemic in several later books, and her ideas were discussed at a 1987 conference devoted to the idea. Her 1990 book Scars of Evolution received some favorable reviews, but the thesis was subject to scathing criticism from the anthropologist John Langdon in 1997 who characterized it as an "umbrella hypothesis" and argued that the hypothesis is not more parsimonious than simply rejecting the hypothesis.

In the last 15 years, one corollary of the hypothesis has received some support within the scientific community: that at some point in the last five million years humans became dependent on essential fatty acids and iodine, which are found in abundance in aquatic resources. Efficient function of the human brain requires these nutrients.

The entirety of the "aquatic ape" proposal remains highly controversial, and is more popular with the lay public than with scientists.

The German pathologist Max Westenhöfer (1871–1957) discussed in 1942 various human characteristics (hairlessness, subcutaneous fat, the regression of the olfactory organ, webbed fingers, direction of the body hair etc.) that could have derived from an aquatic past, quoting several other authors who had made similar speculations. As he did not believe human beings were apes, he believed this might have been during the Cretaceous, contrary to what is possible given the geologic and evolutionary biology evidence available at the time. He stated: "The postulation of an aquatic mode of life during an early stage of human evolution is a tenable hypothesis, for which further inquiry may produce additional supporting evidence." He later abandoned the concept.

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