The aquatic ape theory, championed by Elaine Morgan for years and now making its way into the scientific and popular mainstream, contends that some of our our ancestors dwelled primarily in the water. Morgan recently renewed her case at a TED conference at Oxford, reigniting heated debated among anthropologists.

How Did We Become Hairless? Morgan argued that current theories of human evolution simply don't account for how we got from Point A (chimpanzees) to Point B (modern humans). She noted that the two are quite different despite sharing the vast majority of genes and being separated by only a few million years of evolution. "There, that one, is hairy and walking on four legs. That one is a naked biped. Why?" she asked. "If I'm a good Darwinist I've got to believe there's a reason for that. If we changed so much, something must have happened. What happened?"

Morgan argued that the "hallmarks of mankind, the things that make us different from everybody else" -- from losing our hair to walking on two legs to developing language -- point to a water-borne past. Morgan also cited the elephant, which she once claimed had a hairless ancestor to similar ridicule though that theory has since been accepted. "Every animal that has become naked has been conditioned by water," she said.

Incoherent and Unverifiable. One anthropologist, P.Z. Myers, dismissed the aquatic ape as "a lot of inconsistent and mutually contradictory noise." (His post was followed by an intense, detailed, still-raging debate on the theory.) Greg Laden wrote a lengthy dismantling of Morgan's argument. "The AAT is a zombie theory, untestable because so much of what it proposes has not been framed in a testable way," he concluded. Laden later wrote his real-time reactions to Morgan's TED video, going point-by-point, concluding Morgan had entered "teabagger mode."

Ciaran Brewster, who called Morgan's talk "an idea not worth spreading," believes that we evolved in trees, not water. "Our body shape is a consequence of our adaptation to bipedalism, the requirements of childbirth in women, sexual dimorphism and sexual selection," he wrote. Jim Moore, another anthropologist, built an entire website debunking the aquatic ape.

The Best Theory Right Now? Morgan seemed incredulous at scientists seeking to discredit the aquatic ape. "They are staving off the aquatic theory to protect a vacuum," Morgan lamented, saying that anthropologists have no agreed-upon alternative explanation. "There is nothing there." An exhaustive, if ugly, website run by Algis Kuliukas details the theory and attempts to defend it from criticism. Carole Cadwalladr of the Guardian noted, "[Morgan] has been dismissed as a nutcase for years, but both David Attenborough and Daniel Dennett have recently come around."