Re: Holloway/Morgan

Elaine Morgan (
Fri, 28 Jul 1995 13:14:28 GMT


R. Holloway asked:

Q. Did research into primate sweat really increase?
A. Yes. Elizondo in 1988 reported it had "increased.within the last ten

Q. Was that really due to AAT?
A. No. That was probably a bit of folie de grandeur on my part

Beginners must be baffled by obscure terms like eccrines and apocrines,
so here is a crash course on the differences. Both are skin glands


!. Opens into hair canal Opens onto surface of skin.

2.Milky exudate contains lipids. Clear saline, no lipids.

3. Activated at puberty. From infancy.

4.Exudate produced in gland Mainly an exit channel

5. Common in most mammals Most species have none

6.Serve as sweat glands in non-primates. Sweat glands in some primates

7. In Homo most vanish before birth. Homo has more than any other

8. Original purpose: pheromones. Non-slip grip on ground or branch.

9. Neurotransmitter: noradrenaline. Acetylcholine.

That is the classic picture. As with many biological classifications
the distinctions can get blurred and the functions overlap.

In non-primates eccrines usually occur only on paws e.g.cats. In
primates they are volar (on palms and soles) plus inside of prehensile
tails, knuckle pads, etc. In some monkeys a sparse scattering over the
body, apparently randomly ectopic. In the apes just over 50% of these
skin glands are eccrine. In homo, figure in the high nineties. But the
ape's eccrines do not function.


This century's ace expert on primate skin, Wm. Montagna, said that
man's unique (as he believed) eccrine sweating is so disastrously
inefficient that it must have evolved originally for some other
purpose. It is recklessly and pointlessly wasteful of water and salt,
both scarce resources on the savannah. Their depletion can cause heat
cramps, dehydration, and death. Most hot-climate mammals are
parsimonious with their (apocrine) sweat; if their salt balance is
threatened they may switch to sweating potassium chloride instead of
salt.Our system behaves as if the two things in unlimited supply in
the environment were water and salt.

He didn't speculate on what the original purpose of eccrine sweating
was. So I had a go. Connecting it with the similar pointlessly-profuse
shedding of tears, I thought it might have been another reaction to
"too much salt" (again given the unprovable premise that tears and
sweat were once hypertonic)

It is interesting that, as with tears, we have two kinds of eccrines,
triggered by different stimuli. You may have noticed that your palms
sweat freely from embarrassment or fear, but not at all from heat.

For this theory to be plausible our ancestors must have been subject
to a severe crisis of salinity at one time. In the AAT scenario it
would certainly have been severe when the Sea of Afar began to
evaporate. Some ancestral apes could have been marooned on islands
eating sea-food from water of inexorably increasing salinity until
some of them made it back to the mainland.

Montagna also asked: Why has natural selection endowed the ape with
so many eccrines when it seems to have no use for them? Well, I imagine
the other apes evolved on the landward side of the inland sea, with
limitless forest behind them. They wouldn't need to enter the water
or change their traditional vegetarian diet, but when the sea
receded the salt would have stayed in the soil and been transpired
by the plants for a long time. When ape eccrines no longer served an
excretory purpose they were functionless. Okay: farfetched. The cosy
alternative explanation is..."We may never know..."

By the way, I hope nobody still suspects the Sea of Afar of being a
figment of AAT imagination. It is open to question whether there were
anthropoids there, whether they were affected by the flooding and
whether any of them survived it. But there is no question that the sea
was there, and that it evaporated.

I am asked: Why do no other animals show signs of having ancestors
which underwent this ordeal?. Which ones are you thinking of? If the
sea crashed in anything like the Med crashed through the Straits of
Gibraltar, the original water level in flooded forest areas would be
high. All the herbivores would drown, all the carnivores dependent on
them would perish, the birds would fly to the mainland. The only
mammalian survivors would be the most adaptable of the arboreal ones.

So much for Scars. But Montagna was wrong on one important point and
so was I, for too long. Phil Nicholls recently rubbed my nose in
Elizondo, who reported that the rhesus monkey , and still more the
patas monkey, uses eccrine sweating. I have to admit my case looked
a lot stronger before that damned patas raised its pretty little
head. Of course it is only natural for a hot monkey, finding itself
in possession of those handy little extra holes in its skin which
non-primates do not possess, to let them leak and cool it down.
Voila eccrine sweating. So: case closed? Morgan routed? All
questions answered?

All questions not answered. Note: we are not monkeys, we are apes.
So what Nich et al are now saying is that we resemble the patas in
this way as a result of convergent evolution, no less. When I say
convergent evolution they react as if I used a dirty word.

I am often accused of exaggerating little differences, but the
difference here between ape and human is a quantum leap between nil
and the maximum, between a non-sweater and the champion sweater of
all the primates and indeed, I understand, of all the mammals. Can
you think of a sweatier one?

Why this remarkable difference? Attempts have been made to connect
it with the brain. Peter Wheeler used to talk about our lack of a
carotid rete (a network of veins allowing some herbivores to keep
the head cooler than the body) until he discovered that all primates
lack this rete. Phil Nicholls now argues that bigger brains need
more sweat. Then it should increase pro rata with relative or absolute
brain size. But it doesn't. The brain of the second best sweater (our
friend the patas) is nothing to write home about. And the anthropoid
apes don't use sweat-cooling at all.

Why the difference? Phil helpfully reminds us that the apes keep
cool by behavioural methods: resting in the shade. It works like
a dream. The hominids could have done the same. I will go further:
the newly conventional mosaic scenario implies that in fact they did
do the same. At least part time in the shady trees. Why didn't it work
like a dream for them?

AAT has a powerful reason for why there was a huge difference. By the
time the aquatic ape returned to spending more time on land, it had
lost the precious covering which protects the skin of most land
mammals; it had acquired a thick insulating fat layer; it had extra
weight to carry when it trotted around on the grass. More than enough
reason to need to sweat, and it had to use the eccrines which had
been unfortunately somewhat overspecialised for copious excretion.

I need to know more about patas sweat . Does it ever flow down in
visible streams and drip onto the ground? Does it like ours sometimes
take up to half an hour to react to a rise in temperature? Does it
abate when the monkey is in danger of dehydration?

But most of all I want to know what there was in that ancient
savannah mosaic that is not there in the modern equivalent habitat,
where the savannah chimpanzee effortlessly keeps its cool and says:
"No sweat, man."

Elaine Morgan.