Sir David Attenborough has been derided as "irrelevant" after adding his backing to a controversial theory that humans evolved partly in water.
Sir David told a conference in London that the aquatic ape hypothesis "made more sense" than the conventional savannah narrative accepted by the scientific mainstream.
The aquatic ape theory holds that humans developed large brains and a two-footed gait due to spending large amounts of time in the water.
Sir David said there were serious problems with the conventional hypothesis, while the aquatic theory provided further incentives to preserve marine life.
"Gathering molluscs is far easier than chasing elephants and wildebeests across the savannah," he said.
But scientists immediately rounded on the TV naturalist, saying his theory was not backed up by evidence.
Todd Rae, of the University of Roehampton, said Sir David's celebrity endorsement was a setback as his "national treasure" status lent credence to the claims.
"Adding in an aquatic phase to the evolution of people is like adding yo-yo strings to gravity to explain the movement of the planets," said Dr Rae.
"Because the idea 'makes sense' to them, the data are irrelevant. That is the opposite of science."
Pouring further cold water on the veteran documentary-maker's ideas, Joe Parker, an evolutionary scientist at Queen Mary University of London, asked: "If our transition to an aquatic or semi-aquatic environment was so successful, why aren't we still there?
"For the aquatic ape to work, you have to postulate not one, but in fact two unlikely shifts - into an aquatic niche and then back on to land again."
The conference, entitled Human Evolution Past, Present and Future - Anthropological, Medical and Nutritional Considerations, had already attracted derision, with opponents of the aquatic ape hypothesis launching an online parody advancing the view that humans evolved from "space monkeys".
Conference chairman Professor Rhys Evans, a surgeon at the Royal Marsden Hospital, said: "We are trying to discuss the pros and cons of the theory. But many of the things which are unique to humans - such as a descended larynx, walking upright, fat beneath the skin, and most obviously an extremely large brain - it seems can best be accounted for as adaptations to extended periods in an aquatic environment."
The aquatic ape theory was originally put forward by British biologist Sir Alister Hardy in 1960, who suggested that a waterbound lifestyle could explain why humans had less body hair and more fat under the skin than other apes.