Jim Moore's "AAT Sink or Swim?" Web Site
AAT Claims and Facts: Skin, Sweat and Glands


On this page, Moore criticises Morgan's argument that eccrine sweating is a feature unique to man and aquatic mammals.

His line of attack is again to somewhat exaggerate the argument. He claims that "AATers have long maintained that the patterns of human skin glands, apocrine, eccrine, and sebaeceous, can only be explained by an aquatic past" but gives no citation to back that claim up.

Morgan's original line of thought was really to explain the phenomenon that humans have a predominance of eccrine sweat glands whereas our relatives seem to have progressively greater percentages of apocrine glands the more distantly related they are. She speculated that, perhaps, this was another trait that could be explained by a more aquatic past and, perhaps, was guilty of being a little too over-enthusiastic in looking for evidence in aquatic mammals to back that view up. Moore certainly shows no charity in interpreting an apparent scholarly 'goof up' in this area as poor research at best and a deliberate misrepresentation at worst.

If one remembers that the original observation: that humans sweat more than their primate cousins and we have a far greater percentage of eccrine sweat glands than they do, still has not been given an adequate explanation, Morgan's "crimes" might seem a little less onerous.

It is argued that, once again, these observations might best be understood in the context of a water-side habitat for human ancestors, one where sweat cooling makes most sense, as it is one where precious water can be thrown away for the very short-term gain of a few degrees of localised skin cooling.

Skin, sweat, and glands
Moore starts with the claim that "Morgan and other AATers have long maintained that the patterns of human skin glands, apocrine, eccrine, and sebaeceous, can only be explained by an aquatic past" but, back to his earlier standards, he doesn't make any attempt to back that statement up with any citation.

Difference between the skin of seals and humans
Moore argues that human skin is very unlike that of hairless aquatic mammals and argues that this is why your fingers wrinkle in water, but because he doesn't cite the original AAH, it shouldn't impress anyone. The question is: Did Morgan or anyone suggest that human skin would be like that of hairless aquatic mammals?

"Aquatic eccrine sweating"
In the next section Moore does provide an citation for Morgan's claim that aquatic animals may exhibit eccrine sweating (from 'Scars of Evolution' 1990) , as do humans and having done so, he goes on to accuse Morgan of "poor research" because, according to Moore, she not only got the citation wrong but misunderstood it and/or misrepresented it.
The claim, that fur seals also sweat through eccrine glands, was apparently flawed because the original observation was that "When a heat lamp is focused on the naked flipper of a freshly killed seal, the black epidermis soon begins to blister. Before it does so, droplets appear on the surface of the skin in a fairly regular pattern. These are assumed to be secretions of the sweat glands"  (Scheffer 1962:7.)
Moore triumphantly ridicules Morgan's original assertion: "So the evidence shows that if you fry a dead seal flipper until it blisters, the apocrine glands exude fluid. This is what Morgan claims is 'one clear aquatic instance of eccrine sweat-cooling'".
This scholarly goof-up does not look too good, admittedly, but it does appear that at least part of the problem lies with Ling who also seems to have misrepresented Scheffer's original paper. Perhaps Morgan should have checked the original paper but, as she cited Ling, she can be excused for assuming he had represented his observations correctly.

A charitable view would be that this was, at worst, a simple error but Moore is in no mood for charity. He carries on attacking her with: "...Yet it is this standard of research and evidence Morgan offers as a reason to throw out the last quarter-century of paleoanthropology" and "anyone familiar with Morgan's published and online writing, it is also evident from this particular reference that her standard of evidence for her own theory is far less stringent than what she expects from all others."
Considering the very poor level of references to the actual claims of AAH proponents made on this web site, it seems a little ironic that Moore is so self-righteous in making this criticism

Sebaeceous Glands and the AAT
In the next section Moore takes the AAH to task for claiming that "human sebaeceous glands are an aquatic adaptation."
His arguments against this are on three counts:
1) Many aquatic mammals, e.g. whales and manatees have no sebaceous glands at all.
2) They do provide this function in seal skin but cannot in human skin.
3) Human sebaceous glands appear to have a distinct sexual dimorphism and very different life history indicating that they are more to do with sexual selection.

But Moore ignores the idea that perhaps sebaceous glands provided a waterproofing role, as in seals, at an earlier time which then was no longer required when most of the body hair was lost. The fact that whales and manatees have lost their sebaceous glands completely merely indicates that as they have been hairless for so long, the glands have eventually gone too.
The differences between the sexes might be explained by the differences in the body hair between the sexes and the life cycle changes simply by individuals reaching maturity needing to fend for themselves and, in an aquatic context, therefore needing to do more swimming.

Why all the fuss?
It might be difficult for some to see what all the fuss is about here. The discussion of the function of apocrine and eccrine glands is hardly mainstream to many people.

Perhaps we should remind ourselves about the simple observations which led Morgan to speculate on these matters.

The fact is that prosimians and new world monkeys (with the exception of tree shrews, which some argue should not even be classified as primates) only have apocrine glands in their hairy skin.
Old world monkeys have both apocrine glands and eccrine glands in their hairy skin. Apes do so too, but whereas gibbons and orang-utans have more apocrine glands than eccrine glands, chimpanzees and gorillas have more eccrine glands than apocrine. In humans, we have eccrine glands, almost exclusively, on our hairless body surfaces. (See Montagna 1985:17).

Montagna doesn't speculate as to why this trend might have occurred, merely that it has: "This state of affairs makes it comfortable to explain that man, with the fewest apocrine glands and the most eccrine sweat glands over his general body surface, is the latest model in evolution" Montagna (1985:17).

Morgan, merely speculated that perhaps this peculiar trait too, might be explained by a more aquatic past.
Perhaps she overstretched her argument slightly and was too keen to encompass anything she thought might add weight to this viewpoint but Moore's critique of this point is hardly a fair and balanced account either.

Perhaps the explanation for these changes are simply an increase in sweat cooling in humans over their ancestors. On this subject Montagna writes "since man sweats profusely as a means of temperature regulation, other primates should do likewise. Abundant sweating, however, is peculiar to man: other primates sweat much less." (Montagna 1985:17.)
Moore comes close to this explanation himself when he argues:

Morgan has often made the claim that apocrine glands are more efficient for cooling than eccrine glands, but ignores the advantage of eccrine glands. Apocrine glands discharge their contents and these must be replenished before they're used again, while eccrine glands can go on and on. This allows humans a huge endurance advantage over apocrine sweating animals. The famous example of !Kung hunters running down a giraffe is an example of this advantage. The giraffe's apocrine glands work for only so long before they must recharge, and then the animal must rest or become overheated; this allows the far slower but steadier humans to outlast it and run it down. But does this mean that humans must always be near water? Note that both among the !Kung and Australian aborigines, hunters would often go on long treks far from water without carrying any water, and this in far drier country than our ancestors lived in. Even in the strawman version of savannah ("arid, treeless") that Morgan and other AATers use, carrying water would be unnecessary."

But here, surely, Moore over-stretches his argument too. Is he really arguing that a giraffe is more reliant on fresh water than  a human? It just doesn't  add up.

It seems to me that, once again, the explanation that fits best is one with man living in a water-side habitat.

Montagna, William (1985).
The evolution of human skin. Journal of Human Evolution Vol:14 Pages:13-22