Jim Moore's "AAT Sink or Swim?" Web Site
AAT Claims and Facts: Skin, Sweat and Glands
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
Difference between the
skin of seals and humans
"Aquatic eccrine sweating"
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."
Glands and the AAT
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.
Why all the fuss?
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.
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.)
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.