The idea that humans might have had predominantly aquatic origins dates back at least as far as 1942 when German biologist Maximilian Westenhöfer drew attention to the facts that humans are mostly hairless, have large deposits of subcutaneous fat, and that children are sometimes born with 'webbing' between the fingers and toes.

The hypothesis gained ground in the 1960s with research by Alister Hardy and Elaine Morgan, and with other scientists also citing the human 'diving reflex' usually present in infants.

Mainstream evolutionary theorists, however, were generally opposed to the idea - and some classifying the AAH as 'pseudoscience'.

Although the AAH is now largely sidelined, it's still the subject of some academic debate.

For an overview see :Aquagenesis: Alister Hardy, Elaine Morgan and the Aquatic Ape Hypothesis