Aquatic Ape Hypothesis

In 1960, Sir Alister Hardy, a marine biologist knighted for his contribution to the fisheries industry, gave a talk at the British Sub-Aqua Club (a scuba-diving club) and a month later published an article in New Scientist on that talk, called “Was Man More Aquatic in the Past?” Although the idea caught people's fancies and garnered some attention by the newspapers, it showed little sign of the long-lasting popular appeal it would eventually have.

It didn't happen overnight. Even with the original article and a follow-up transcript from a radio program, it was 7 years before Hardy's idea got much notice—this time with a two-page write-up by Desmond Morris in The Naked Ape.

Elaine Morgan, at the time an Oxford graduate in English and a TV scriptwriter, entered the scene in 1972 with the book Descent of Women, the idea for which she got from Desmond Morris's book. This book proved to be very popular, and in time Morgan followed it up with many articles as well as four more books on the subject (in 1982, 1990, 1994, and 1997).

During the 1980s, other proponents arrived on the scene, chief among them a medical doctor from Belgium, Marc Verhaegen. A 1987 conference on the subject resulted in a book presenting opposing views, The Aquatic Ape: Fact or Fiction?

The coming of age of the Internet in the 1990s brought the advent of the online venue for presentation and debate, and this subject proved popular. As with many subjects connected with humans and especially human evolution, much of the debate is rancorous and ill-informed. There are nuggets of gold in the online debate; however, just as with the mineral, finding these nuggets requires a lot of panning.

The Aquatic Ape Theory or Aquatic Ape Hypothesis (aka AAT or AAH—this entry will refer to it as the AAT/H) hypothesizes that humans went through an aquatic or semiaquatic stage in our evolution, generally said to have occurred during the transition from the last common ancestor we shared with apes (LCA) to hominids (some, like Marc Verhaegen, claim it continued on through virtually the entire span of human evolution). It claims that certain features are seen in human anatomy and physiology that are only seen in humans and aquatic animals and that these constitute conclusive evidence that our ancestors went through an semiaquatic phase in our evolution. Relying heavily on the principle of convergent evolution, it says that life in an aquatic environment explains these features and that a transition from ape to hominid in a nonaquatic environment cannot. The principle of convergence is used to explain these features, and the idea is said to be more parsimonious than other hypotheses.

Their use of the idea of convergence is generally accurate, but generally, they use parsimony to mean that only one cause explains many features (a more accurate term might be “prime mover” or “umbrella hypothesis,” the latter being one that AAT/H critic John Langdon uses).

One problem with the idea is that most of the proponents have been rather vague about the degree of aquaticness to which they refer. One proponent, doctoral student Algis Kuliukas, has come up with an explanation apparently also now endorsed by Elaine Morgan, that water has acted as more of an agent of selection in human evolution than in the evolution of apes such that physical differences between the two may be at least partly explained as adaptations to more efficient movement through acquatic conditions. This definition is perhaps most notable for its vagueness, merely suggesting “more” water use by humans than by apes. Contrast that with the explanation set forth in by Bininda-Emonds, Gittleman, and Kelly: “We consider aquatic carnivores to be those species in which the aquatic habitat inevitably plays a key role in the life-cycle of an individual,” which they then compare to definitions as given by others as they discuss the strengths and limitations of their own definition. The AAT/H definition suggested is not only so vague as to be virtually meaningless, it is notable that this is the first attempt at such an explicit definition, and it has taken over 40 years to show up. There has always been an implicit “how aquatic” definition, however, ascertained by the characteristics the proponents have used to build their case.

...