Based on current human characteristics, it's entirely reasonable to hypothesize some degree of adaptation to a littoral lifestyle. The shores in question could have been at ponds, rivers, lakes, or sea coasts, or all of them. There's no necessary contradiction with the hot-dry savannah model, because humans could have been the apes concentrated around the rivers or water holes. (That said, Elaine Morgan ran rather far ahead of the facts in some of her work.)
As for the characteristics:
webbed hands: compared to other great apes, we have very flexible hands and can spread our fingers much farther. The latter alone could account for what seems like a "webbed" effect. In other words, our hands aren't webbed in the sense that a duck's feet are.
nakedness, subcutaneous fat layer, ability to hold breath: definite arguments for adaptation to frequent immersion.
bipedalism: adequately explained by the selective advantage conferred by having a free hand, even two free hands. Tool use, ability to carry larger-brained infants, etc., etc. Really a stretch to call this an indication of adaptation to aquatic lifestyles.
water birthing: under the levels of asepsis present in the natural environment would lead to what we biologists call strong negative selective pressure. In other words, infections would kill mother and probably child at such elevated rates that women who had the sense to stay OUT of the water would tend to have many more surviving offspring.
nutrition: omega-3 fatty acids. If we spent a lot of time being littoral apes, who knows?, maybe we ate lots of freshwater clams? Need for omega-3 could also be relatively recent development, in that we may have lost the ability to synthesize our own recently. Also, we don't need much, and can survive long enough to reproduce with practically none in the diet. Seems a very weak argument to say that this is evidence of an aquatic lifestyle.
Tears: pure bunk. The amount of salt we lose through tears is, well, microscopic. Unless being expelled from Paradise led to a lot more weeping than seems reasonable, this idea makes no sense. We do lose salt through sweating, but that seems more of a side-effect than an adaptation.
Mating position: Given bipedalism and the ability to have sex in all kinds of ways, the question isn't "Why?" but "Why not?" Through most of our history as a species, women haven't spent their adult lives swaddled in tents. When women can go for the sex they want, I can imagine several reasons, which have nothing to do with aqautic lifestyles, why men with more versatility could be more interesting.
To sum up, we have some adaptations that look a lot like what you'd expect in an animal that's in and out of the water quite a bit. However, the "Aquatic Ape Hypothesis" goes well beyond the facts, and even contradicts some of them. |
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