1. From the fact that many humans today have a lot of body hair, we can safely surmise that this feature varied during the time span of our species, Homo sapiens sapiens, instead of changing -- as the AAT/H typically requires -- during the transition from the LCA to hominid (LCA = last common ancestor between apes and hominids).
2. A great many, probably most, types of aquatic mammals are hairy, so we see that losing body hair is not an aquatic feature. Some aquatic mammals don't have body hair; most of these are very large mammals, just like the land mammals which have little body hair. The reason large mammals tend to not have body hair is that they overheat if they have it (large shapes have a ratio of less surface area to volume than small shapes, so they lose heat slower). Note: At this spot on this page I previously made the incorrect statement here that phocid seals (also called eared seals or true seals) don't have body hair. That is not so; they are well-covered with stiff hair.

Clearly human skin is very unlike that of hairless aquatic mammals. Unlike the skin of these aquatic mammals, human skin quickly becomes waterlogged (this is why your fingertips wrinkle when you're in water), an obviously undesirable trait for a purportedly aquatic animal.

Body hair and convergent evolution

The aquatic ape theory uses the evolutionary concept of convergence to explain why aquatic mammals have little or no body hair.  Ignore for a moment the undeniable fact that aquatic mammals don't always (in fact, don't usually) have little or no body hair, and look at the principle of convergence as it relates to this loss of body hair. How does hair or the lack thereof fit into the principle of convergence? Does the AAT/H explain this feature?

Assume for a moment that humans today are pretty much the same in terms of having little or no body hair -- okay, I know it isn't true, you know it isn't true, anyone who takes a moment to think or who has ever seen Robin Williams take his shirt off in a movie knows it isn't true, but for a moment, pretend it is true. Then we have several groups of mammals which have little or no body hair: extremely large mammals, extremely fast-swimming mammals with specialized skin, naked mole rats, some pigs, and humans. The group of extremely large mammals include elephants, hippos and rhinos, as well as whales, manatees and dugongs. Walruses, Northern sea lions (Steller sea lion), and elephant seals are often said to be in this group, but they do have hair over almost all of their bodies. The group of extremely fast-swimming mammals with specialized skin includes porpoises and orcas, and some of those aforementioned whales. Humans quite obviously don't fit into any of these categories, so right away we can see that the AAT/H seems doomed to fail to explain this supposed hairlessness of humans by claiming it's a convergent aquatic evolutionary trait. The question that AAT/H proponents typically fail to ask is: what about that necessary feature of evolutionary convergence, similarity in function?

Mostly AAT/H proponents are coy on this point, declining to point to any such similarity, as if mere contact with water. even just wading, is enough to create this change. Those that are more honest in their theorizing can come up with only one reason: to swim faster. Looking at the list above, we can see that it seems to be the only possible reason. But is it a sensible reason? Would selection pressure have worked its magic on this feature to make us faster swimmers during an aquatic phase?

Catching fast food and escaping aquatic predators would seem like a good idea to say the least, but would losing our body hair have done it? There are two parts to this, does it make us faster? and is "fast" fast? Second question first: human swimmers are, sadly, pathetically slow. The fastest human swimmers in the fastest Olympic event can't quite manage 6 miles per hour, and they're one heck of a lot faster than average people (twice as fast or faster). Given the long legs which propel them, we can be pretty sure that they're one heck of a lot faster than our early ancestors too. Yet 6 miles per hour is slow; it's a speed which can be easily exceeded on land by children (that fat kid down the block can do better than 6 mph). It's also deadly slow in the water, crocs and sharks are several times faster. A shark wouldn't even have to kick into high gear to catch an Olympic swimmer (assuming the swimmer saw the shark coming, which is a whole other ball of wax -- see the section on predators).

Now for the first question, does lack of body hair make us faster swimmers? Sure, we already know it can't make us fast enough, but does it make us faster at all? Since we've seen swimmers shave their body hair for years now, it might surprise you as it did me to find that there was no real attempt to experiment and see if it actually worked until fairly recently.

When I looked this up some time back, in literature on sports physiology, I found one study which showed an effect that could possibly help swimming speed, although actually helping swimming speed was not demonstrated. ("Influence of body hair removal on physiological responses during breaststroke swimming", Rick L. Sharp and David L. Costill, Medicine and Science in Sports and Exercise 1989: 21(5), pp. 576-580.) That study showed a difference in build-up of lactic acid in the muscles in athletes who had shaved their bodies, a slight increase in distance per swim stroke, and an "insignificant decline" in heart rate, which all together indicated reduced effort in swimming. This, it was assumed, would lead to an increase in swimming speed. They also showed a slight increase in coasting distance (compared to a control group) when a swimmer dove into a pool when that swimmer had shaved their body hair. These differences, they felt, could be as high as 3-4%, which would work out -- for the fastest Olympic swimmers in the fastest event -- to as much as one-quarter of a mile per hour. This would be important for competition swimmers, where an increase in a quarter mile per hour might easily mean the difference between defeat and victory against other human swimmers, but against swimmers -- like crocs and sharks -- that still swim 2-5 times faster, it would have a negligible effect.

The other experiment I know of related to hair and swimming speed showed a decrease in drag in seals when hair is present. In the book Mammal Skin (1982) Sokolov describes experiments which showed this effect: "Experiments on models covered with the skins of Phoca vitulina and Pusa sibirica show a reduction in drag as compared with rough, bare skin. Hence the damping role of pinniped pelage during swimming (Mordvinov and Kurbatov, 1972). A hydrodynamic tube experiment with a dummy having a Baikal sealskin pasted over it reveals that hair is conducive to an increase in the boundary layer thickness, to a reduction of the speed pulsation level within 1 to 10 khz, and to a reduction in drag." (Sokolov 1982: 60; Mammal Skin by V.E. Sokolov, University of California Press: Berkeley).

So is smooth better? The jury is still out. The past few years many more competition swimmers have been wearing body suits, but some say new records are not due to the suits. And if the newfound speed is due to these suits? The characteristics of these suits make them additional arguments against the AAT/H position on hairlessness, since they are ridged fabrics. The idea behind the suits is to recreate the same effect as seen in that experiment with that hairy sealskin and the skin of dolphins, which is covered with very small ridges. Of course the AAT/H wants it both ways; smooth bodies and hairy heads. At any rate, the speed isn't nearly enough; sharks and crocs would literally have an Olympic swimmer for lunch in a contest of swimming speed.

One AAT/H proponent has taken my points above as evidence for an aquatic background. His mistakes in doing so are instructive.

First, he continued a long-standing AAT/H tradition of dishonestly reporting only part of the evidence I found; the part about the study that points to hair removal as possibly producing a slight benefit in speed. But he ignored the other two items of evidence I also found, both of which suggest the opposite effect. While the research I found showed conflicting, and therefore, inconclusive, data, he turned that into non-conflicting and conclusive data (and another AAT/H "false fact") by dishonestly reporting only that part of the data he'd seen which supported his position (and since he read it here in the above paragraphs, we can be sure he was dishonest in his omissions).

Second, he made an error in reasoning by asserting this speed increase would help individual, less-hairy hominids because they would swim faster and be at the front of a fleeing pack of which the rearmost individuals would be most at risk. There are several problems with this assumption. One is that what he describes is seen only in animals which form extremely large herds or schools (unlike any ape/hominid groups) and/or which are not incredibly slow compared to their potential predators (unlike us versus crocs or sharks). Another is that, as my section on aquatic predators explains in detail, these aquatic predators are rarely seen until they have already struck -- in the vast majority of cases, fleeing never comes into the picture.

Perhaps most instructive is what his reaction says about an all too typical AAT/H proponent's attitude toward data. I reported all the data I found on hair and swimming speed, both suggesting that hair helped and that suggesting no hair helped, and I did this because that's the way you do science -- it's the only honest and sensible way to do it -- but he assumed that I did so "by mistake" . That he would assume so tells us a lot, I'm afraid, about his own attitudes toward data, and what it tells us is not good, and certainly not reassuring vis a vis the reliability of AAT/H proponents' research.

Summary

1. We know that humans today are one single species.
2. We know that humans today vary in body hairiness, and in length of head hair.
3. We know that these characteristics vary regionally.

Therefore, since we see that either of these characteristics can come and/or go that quickly (a few 10s of thousands of years or less), any theory claiming it happened during the transition from common ancestor to hominid can only be an unwarranted assumption. Yet this is what the AAT/H states, and this unwarranted assumption is what AAT/H proponents consider a key piece of evidence for their view.

The change from the ancestral characteristics of body and head hair -- whatever those characteristics might have been -- may have happened first during the timespan of Homo sapiens sapiens, or it is possible that it changed and rechanged many times before that. But we do know that it can, and did, change quickly, and that it has changed during the timespan of our species.

So besides the intractable problem that changes in body hair would be insignificant in terms of swimming speed, the speculation in the AAT/H about how these hair characteristics changed has three basic problems:

1. In both cases, the AAT/H speculates a change into a characteristic which is not a characteristic of our species, just of some members of our species; and
2. since we know these characteristics changed during the span of our species, the AAT/H explanation that it happened millions of years before that must be incorrect; unless
3. it's treated as a sort of nonsense speculation, like speculating that we may have had stripes for a few million years but they disappeared without a trace.