High Quality Content by WIKIPEDIA articles! The aquatic ape hypothesis (AAH) is an alternative explanation of some characteristics of human evolution which hypothesizes that the common ancestors of modern humans spent a period of time adapting to life in a partially aquatic environment. The hypothesis is based on differences between humans and other great apes, and apparent similarities between humans and some aquatic mammals. First proposed in 1942 and expanded in 1960, its greatest proponent has been the writer Elaine Morgan, who has spent more than forty years discussing the AAH.