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Female western lowland gorilla
A female western lowland gorilla walks through a river. Some scientists believe our ancestors lived an aquatic lifestyle. Photograph: Getty



"Humans are very different from other apes," said Peter Rhys Evans, an organiser of Human Evolution: Past, Present and Future. "We lack fur, walk upright, have big brains and subcutaneous fat and have a descended larynx, a feature common among aquatic animals but not apes."




"Humans have particularly large sinuses, spaces in the skull between our cheeks, noses and foreheads," he added. "But why do we have empty spaces in our heads? It makes no sense until we consider the evolutionary perspective. Then it becomes clear: our sinuses acted as buoyancy aids that helped keep our heads above water."


"I think that wading in a watery environment is as good an explanation, at the moment, for our upright gait as any other theory for human bipedalism," said Professor Chris Stringer of the Natural History Museum, London. "But the whole aquatic ape package includes attributes that appeared at very different times in our evolution. If they were all the result of our lives in watery environments, we would have to have spent millions of years there and there is no evidence for this - not to mention like crocodiles and other creatures would have made the water a very dangerous place."

It is not just human physiology that reveals our aquatic past, argue the theory's supporters. Our brain biochemistry is also revealing. "Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is found in large amounts in seafood," said Dr Michael Crawford, of Imperial College London.



Birth of a notion

Originally outlined by biologist Alister Hardy, the aquatic ape hypothesis achieved prominence when the theory was taken up by the Welsh writer Elaine Morgan in the early 70s. (Her previous work had included writing episodes of Dr Finlay's Casebook.)

Morgan became infuriated with male-dominated explanations for human attributes such as hairlessness. According to prevailing ideas, human males lost their body hair when they took up hunting and needed to sweat profusely in the African heat. But no explanation was given to account for loss of female body hair. As a result, Morgan turned to the aquatic ape theory, which she believed provided a more balanced vision of human evolution. Morgan wrote a popular account of the theory, The Descent of Women, which became a bestseller on both sides of the Atlantic. She followed this up with other books on the subject, including The Scars of Evolution and The Aquatic Ape Hypothesis. Most recently, Morgan defended her belief at a TedX presentation in 2009.

• This article was amended on Saturday 27 April 2013 to add a "no" to this quote: "we would have to have spent millions of years there and there is evidence for this".

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