Were Humans Once Aquatic Apes?

The idea that recent human ancestors may have once lived in the water is not taken seriously, but raises interesting questions.

There is no doubt at all in the scientific community that modern human beings diverged from their closest ape ancestors — the chimpanzees and bonobos — around five or six million years ago. Fossil evidence of human evolution, while still somewhat sketchy in the fine details, is unequivocal in its general demonstration of the close relationship between humans and apes. Add to this the genetic certainty that Homo sapiens share about 98% of their genome with that of their ape forebears, and the picture becomes even clearer.

But despite the obvious similarities, there are enough differences between humans and apes to spawn intriguing hypotheses. One of the strangest and most controversial of these is the so-called "aquatic ape" theory.

Was There An Aquatic Interlude In Human Evolution? - Image Serenity

Humans Built For Swimming?

Sir Alister Hardy, a British scientist, in 1960 first put forward the idea of a period in humans' evolution when they were partially or entirely aquatic before later returning to land. As evidence of his hypothesis, he pointed to many physical features of humans that differ markedly from those of other apes, features that seem to have more in common with mammals that live in the water today or lived in the water at some point in the past.

Hardy argued, for example, that humans are not covered in fur as other apes are, but instead have naked skin more suited to swimming, as dolphins, whales and manatees have. He also noted that the hair humans do possess occurs in a diagonal pattern on the body, perhaps having the effect of streamlining the form in the water.

Body Fat and Holding Breath

In addition, humans also have a layer of subcutaneous fat distributed fairly evenly all around the body, similar to other aquatic mammals and unlike other apes, who tend to store fat in specific areas of the body. The fat could theoretically serve to keep the human body warm and buoyant in the water, as well as enhance the streamlining effect of the hairless skin.

Other features Hardy highlighted in describing his aquatic ape theory are the fact that humans possess downward-pointing nostrils that are ideal for diving; that humans cry salty tears, which could have removed excess salt from the body in an oceanic environment; and that humans are the only known mammals that can deliberately hold their breath.

Walking Upright in a Flood

Even the evolution of bipedalism in humans has been attributed to the aquatic ape scenario. Science writer Elaine Morgan, who has written several books on the subject, argues that humans could have begun walking on two legs in order to better maneuver around coastal environments or areas where flooding was common, further pointing out that a partially aquatic lifestyle might have eased some of the modern scourges of bipedal walking, such as lower back pain and varicose veins; the buoyancy of the water would have made these problems less severe.

A Fringe Theory

It should be noted that the aquatic ape theory is not generally taken seriously in the scientific community. Skeptics point out that the hypothesis makes no compelling predictions and is at bottom nothing more than a loose description of human physical features that might be accounted for in other ways. And though the human fossil record is still somewhat spotty, and might even be sparse enough to accommodate a brief aquatic period in its long history, the fact remains that fossil evidence does not so far support the idea of a once-aquatic human.

Source:

Ingram, Jay. "Homo Aquaticus." The Barmaid's Brain and Other Strange Tales from Science. New York: W.H. Freeman. 102-17. Print.