Aquatic Ape Hypothesis

The aquatic ape hypothesis (AAH) is a hypothesis about human evolution, which posits that the ancestors of modern humans spent a period of time adapting to life in a wet environment. AAH emerged from the observation that some traits that set humans apart from other primates have parallels in aquatic mammals. It was first proposed by German pathologist Max Westenhöfer in 1942, and then independently by British marine biologist Alister Hardy in 1960. After Hardy, the most prominent proponent has been British screenwriter Elaine Morgan, who has written several books on the topic.

AAH has not been accepted among the mainstream explanations of human evolution. Scientific consensus is that humans first evolved in East Africa in a period when the climate fluctuated between wet and dry, and that most of the adaptations that distinguish humans from the great apes are adaptations to a terrestrial, as opposed to an earlier arboreal, environment. Few paleoanthropologists have explicitly evaluated AAH in scientific journals, and those that have reviewed the theory have been critical. An extensive criticism appeared in a peer reviewed paper by John H. Langdon in 1997. Langdon argued that the AAH is one of many hypotheses attempting to explain human evolution through a single causal mechanism, and that the evolutionary fossil record does not support such a proposal. Langdon also argued that the hypothesis is internally inconsistent, has less explanatory power than its proponents claim, and that alternative terrestrial hypotheses are much better supported. AAH is popular among laypeople and has continued support by a minority of scholars. Langdon attributes this to the attraction of simplistic single-cause theories over the much more complex, but better supported models with multiple causality.