Scientists find it easy to explain why we resemble the African apes so closely by pointing out that gorillas, chimpanzees and humans share a common ancestor.
It is much harder to explain why we differ from the gorilla and the chimpanzee much more markedly than they differ from one another. Something must have happened to cause one section of the ancestral ape population to proceed along an entirely different evolutionary path.
The most widely held theory, still taught in schools and universities, is that we are descended from apes which moved out of the forests onto the grasslands of the open savannah. The distinctly human features are thus supposed to be adaptations to a savannah environment.
In that case, we would expect to find at least some of these adaptations to be paralleled in other savannah mammals. But there is not a single instance of this, not even among species like baboons and vervets, which are descended from forest- dwelling ancestors.
This awkward fact has not caused savannah theorists to abandon their hypothesis, but it leaves a lot of problems unanswered. For example, on the question of why humans lost their body hair, it has been argued at various times that no explanation is called for, or that we may never know the reason, or even that there may not be a reason. These attitudes seem to be not merely defeatist, but fundamentally unscientific.
The Aquatic Ape Theory (AAT) offers an alternative scenario. It suggests that when our ancestors moved onto the savannah they were already different from the apes; that nakedness, bipedalism, and other modifications had begun to evolve much earlier, when the ape and human lines first diverged.
AAT points out that most of the “enigmatic” features of human physiology, though rare or even unique among land mammals, are common in aquatic ones. If we postulate that our earliest ancestors had found themselves living for a prolonged period in a flooded, semi-aquatic habitat, most of the unsolved problems become much easier to unravel.
There is powerful geological evidence to support this hypothesis, and nothing in the fossil record that is inconsistent with it. Some of the issues it raises are briefly outlined in the following pages.
There are a wide range of physiological traits in human beings that can be explained by an evolutionary period in human existence that involved a partial, complete and then semi-aquatic phase in human prehistory.
ChararacteristicsHumansApesSavannahAquaticsHabitual BipedalismYes–––Loss of body hairYes–YesYesSkin-bonded fat depositsYes––YesVentro-ventral copulationYesYes–YesDimunition of apocrine glandsYes––YesHymenYes––YesEnlarged sebaceous glandsYes––YesPsychic tearsYes––YesLoss of vibrissaeYes––YesVolitional breath controlYes––YesEccrine thermoregulationYes––YesDescended larynxYes––Yes
The Aquatic phase took place more than 5 million years ago. Since then, Homo has had five million years to re-adapt to terrestrial life. It is not surprising that the traces of aquatic adaptation have become partially obliterated and have gone unrecognized for so long. But the traces are still there as the table indicates.
Dear Straight Dope:
A few years ago, Elaine Morgan published a book called The Aquatic Ape that publicized a theory that humans, at some time in their evolution, had partially adapted to a marine environment. This theory had first been proposed by an English marine biologist named Alister Hardy (if I remember correctly) and was held to explain a host of differences between Homo sapiens and the rest of the great apes, among them:
relative hairlessness, subcutaneous body fat, bipedality (to make swimming and wading more efficient), a “diving reflex” to prevent drowning in infants, our horrendously inefficient water management system, our lack of fear of the water, the webbing some people have between their fingers and toes, and so on.
The theory seemed reasonable enough to me, but every time I’ve heard paleontologists refer to it, they seem to be rolling their eyes the way archeologists do when you mention James Churchward to them. What do these guys know that Hardy and Morgan and I don’t?
— John La Torre,