Jim Moore's "AAT Sink or Swim?" Web Site
AAT Claims and Facts: Fat and the AAT
This page could be argued to contain some of Moore's strongest arguments on his web. He quotes extensively from Caroline Pond, a reputed authority on one of the traits AAH proponents have claimed 'as one of their own' for years, the relatively high level of fat in humans. Pond is someone who has made no secret of her lack of support for the AAH and the idea that increased fat content in humans may be symptomatic of a more aquatic past and so, on the face of it, Moore would appear to have a sitting duck to shoot at. Moore even promotes one rather plausible explanation for our increased adipose tissue of his own which deserves merit, namely that becoming isolated away from predators would tend to reduce the competitive need to stay lean.
However even here Moore, and his champion Pond, appear to assume many of the typically exaggerated positions of the AAH to make their case. Pond's arguments against the AAH, for example, seem to be largely based upon the notion that the distribution of fat in humans only appears to be analogous to marine mammals like whales but is actually distributed very differently and rather like most terrestrial mammals. She argues that human adipose tissue would not be much use as a thermoregulatory device, but neglects the fact that the AAH is not claiming that man lived in the sea, merely that he went into the water regularly for food. In a tropical habitat, going for regular, relatively short swims in the sea might seem to many to be an ideal way of life on the beach. So, if one takes away the assumption that out ancestors spent very long spells in the water, that major objection simply sinks like a stone.
Floating is, of course, one of the main aquatic arguments for increased fat content, and it is one that both Pond and Moore completely ignore. Again, it is in a habitat at the water's edge, and not in a fully aquatic lifestyle like a marine mammal, that increased buoyancy makes most sense.
On this page, Moore makes twelve (again unattributed) claims about the AAH on the subject of fat. Three are wrong in their factual basis and seem to be a deliberate attempt at misrepresenting Morgan's argument (see points 1, 2 & 3 below). Two make unsubstantiated claims which appear to argue against the AAH but on closer examination appear to be, at best, ambiguous. (9, 11) Five are partially correct but exaggerate the AAH position to an unsustainable position (5, 6, 7, 8, 10). One is factually accurate but makes a point that Morgan made herself (4) and one is a valid point against the original Hardy/Morgan proposal but not against other AAH models. (12).
Overall, even this 'sitting duck' got away. If one
assumes a moderate version of the AAH, one postulating merely that human
ancestors were more aquatic than the ancestors of apes then Ponds and
Moore's objections have to be removed. Fat for greater buoyancy is an
entirely plausible explanation for a hominid that lived at the water's edge.
Fat and the
Having made this, rather mixed opening, Moore then goes onto to outline x points about the AAH argument for fat which he believes are wrong.
He introduces this in a rather aggressive way suggesting that Morgan's approach, like with Salt and tears (see x for that) that she finds a leading expert in a field and "then completely misrepresenting what that expert says". That's quite an accusation. Let's see if it stands up to scrutiny. I'm trying to extract the actual points of contention from the text to make the argument a little clearer.
uses Pond's observations that humans are fat mammals but ignores Pond's
observation that the fat in humans is similar to that of captive monkeys if
they aren't kept on a strict diet."
So how could Moore make such a claim? He has selected the fragments of the paper suits his argument best and paraded it as if it proves Morgan wrong. Firstly, Pond's statement that the "distribution of human adipose tissue is similar to that of exceptionally obese monkeys" (Pond 1987:p63) seems to take on special meaning in Moore's view. Secondly, she does indeed suggest that ".. a few of the monkeys kept ... became obese at more than 25%..." and of course Moore cites that on his page. However he fails to mention that similarly obese humans get to 40% fat in women and 28% fat in men.
It would appear that it is not Morgan who is misrepresenting Pond here but, if anyone, it's Moore.
misrepresents Pond's point that mice models are inappropriate comparisons
with humans because their adipocytes can grow whereas humans multiple,
making it harder to lose weight once it has been put on.
wrote that this type of adipocyte is found humans, fin whales, hedgehogs,
monkeys, and badgers but Morgan ignored all but the "whales" part of that
4) Pond has
also pointed out that human fat distribution, unlike that of whales and
seals, indicates that it was not part of an aquatic adaptation.
understanding of the aquatic ape. It would be good to think that statements like "Hardy and Morgan believe that humans were aquatic [my emphasis] at some stage of their evolution from ape-like ancestors" (Pond 1987:p65) were shorthand for a long winded, but more precise, definition but when she makes further comments like "They think that the hair, skin and superficial adipose tissue of humans evolved into "blubber", similar in function to that of seals and whales." and "In specialised aquatic mammals such as whales, seals and manatees the limbs are reduced or absent and the trunk is smooth and tapered" one gets the impression that she too, is pushing the aquatic 'boat' out a little too far.
She writes "No one can claim that the limbs and trunk of humans have evolved
further towards fully aquatic habits than those of the otter" (Pond
1987:p65) when, of course, Hardy made precisely the point that he didn't
consider man's ancestors to have ever been more aquatic than an otter.
claimed that fat was an adaptation for insulation in an aquatic environment
again contradicting Pond.
Morgan wrote "I found it hard to understand why she described the insulation hypothesis as 'a major tenet of the so-called "Aquatic Ape Theory". It was, as we have seen, equally a tenet of the savannah theory that hominids lapped themselves in a coat of fat to keep them warm at night . As for the AAT, if buoyancy is included as an auxiliary function of the fat layer, that can only be good news. Water is the only habitat in which it would be relevant." Morgan (1997:p97)
As argued before, perhaps the main aquatic aspect of human fat is the extra buoyancy it gives. This is the AAH argument here which tends to get overlooked because it is rather clear that humans are more buoyant than chimpanzees and probably goes a long way to explaining the relative difference in swimming abilities between the two species.
argues that the major role of fat is as a food supply rather than insulation even in arctic species
where it probably only plays a minor role.
argues that the reasons for the differences seen in fat distribution in
different species seem to be for shaping, and in humans it acts for sexual
8) The life
history of fat development in humans and aquatics is very different.
Moore says "For these human fat characteristics to be due to an aquatic adaptation, we would have to be aquatic as babies, non-aquatic as children, aquatic again in puberty, and even more aquatic in our old age. And females would have to be far more aquatic than males, but only from puberty on. It just doesn't make sense as an aquatic adaptation, but it makes perfect sense as a feature developed as a result of sexual selection."
This is a reasonable point but, again, it assumes that the AAH. by drawing upon the analogy of the greater fat content of aquatic mammals, is arguing that human ancestors lived the same kind of lifestyle as whales and seals.
argued for years that people shouldn't just assume fat in terrestrial
animals had one use. She wrote
"One of the most striking features of adipose tissue in mammals is that it
is associated with so many different tissues. Yet most biologists believe
that all adipose tissue behaves in much the same way, regardless of which
specific depot it comes from" (Pond 1987:p62)
bears, according to the AAT, should have a fat distribution that is quite
different from their more terrestrial relatives, considering their more
aquatic lifestyle, but it doesn't.
bear's fat layer, which is three to four inches thick, not only protects it
from the cold, but adds to its bouyancy in the water.
"The Polar Bear has a thick, well-insulated fur coat and a layer of fat which protects its body from the intense Arctic cold." www.panda.org
Also a paper written by Cattet et al did conclude that "The adipose tissue fo polar bears had a lower water content and a higher proportion of long chain fatty acids than did the adipose tissue of black bear, when compared at equal lipid content" Cattet et al (2001). Although this paper did not look at overall fat levels but the chemical composition of the fat itself, it would appear that there are significant differences between the fat in polar bears and in their more terrestrial cousins.
According to Pond, fat isn't a particularly good insulator anyway.
issue of high human infant fat is explained by the large human brain as
pointed out by Jane Lancaster.
Measuring fat in modern humans probably does not give an accurate measure of
the level in the rudimentary tool-using populations of 5 Ma.
It's a strong and persuasive argument, for sure, but is it even contradictory to the AAH model? Wouldn't this exact phenomenon also be likely to have happened If some of our hominid ancestors had become isolated on islands? If they had, would not increased swimming and diving also have been likely to have resulted, and would not increased adipose tissue be predicted in those situations, irrespective to the predation argument?
Fichtelius, Karl-Erich (1991). More Thoughts on the Aquatic Ape Theory: How the aquatic adaptations of man differ from those of the gorilla and the chimpanzee. In: Roede, Machteld; Wind, Jan; Patrick, John; Reynolds, Vernon (eds.), (1991). Aquatic Ape: Fact of Fiction: Proceedings from the Valkenburg Conference. Souvenir Press (London)
Lenfant, C. (1969) Physiological properties of the blood of marine mammals. In The Biology of Marine Mammals. ed. H T Anderson (New York: Academic press)
Lin, Yu-Chong (1982). Breath-hold Diving in Terrestrial Mammals. Exercise in Sport Science Review Vol:10 Pages:270-307
Morgan, Elaine (1982). The Aquatic Ape Theory. Souvenir Press (London)
Morgan, Elaine (1982). The Aquatic Ape Theory. Souvenir Press (London)
Morgan, Elaine (1990). The Scars of Evolution. Oxford University Press (Oxford)
Morgan, Elaine (1997). The Aquatic Ape Hypothesis. Souvenir Press (London)
Pond, Caroline M (1987). Fat and Figures. New Scientist Vol: Pages:62-66
Pond, Caroline M (1987). The Anatomy of Adipose Tissue in Captive Macaca
Monkeys and Its Implications for Human Biology. Folia Primatologica Vol:48