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 AAT
On this page Moore attacks what he, correctly, identifies as "the  feature that apparently started the AAT ball rolling". He cites Hardy and Morgan as having espoused this idea from the principle of "convergent evolution" - aquatic mammals such as seals and whales  have thick layers of sub-cutaneous fat for 'aquatic reasons' so too, probably, have we.
Moore then says "They claim that it is bonded to the skin and not internally, as in our primate relatives. They're wrong." He makes no attempt to give a citation for this claim, perhaps because he couldn't find one. In fact, as we've seen already, this is not wrong. William Montagna made this abundantly clear when he wrote this about the juxtaposition of human fat's association with the the skin... "Together with the loss of a furry cover, human skin acquired a hypodermal fatty layer (panniculus adiposus) which is considerably thicker than that found in other primates, or mammals for that matter." Montagna (1985:p14).

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.

1) "Morgan 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."
Moore is clearly keen to downplay the differences in fat between humans and primates. He has already ignored Montagna's observation that the human hypodermal layer is "thicker than found in other primates or mammals for that matter" and here he is downplaying Pond's equally clear statements and data which indicate that there are significant differences in the amount of fat too.
Moore, later, quotes several passages from Pond's New Scientist 1987 article but missed out one sentence of clear relevance here: "Most human beings are as fat or fatter than the fattest of our monkeys, [my emphasis] so it is not surprising that the paunch and other superficial depots are conspicuous under our thin, hairless skin" Pond (1987:p63).
Another fact Pond gives, but which Moore, fails to mention is that "the minimum fatness recorded for teenage girl athletes is 7%, and for men about 5%." (Pond 1987:p63) This should be contrasted with her statement that "more than half the 31 captive monkeys that we examined were less than 5% fat, thinner than most laboratory rodents, although all of them had continuous access to food and little opportunity to exercise.".
Pond's chart, also on page 63, shows that humans have 10x the number of adipoctyes expected for a carnivore of similar body mass and almost 100x more than for a similarly sized non-ruminant  herbivore, or for the mid-range of the monkeys studied in her data.
The caption for that chart starts: "Comparisons with other mammals show that Homo is clearly the odd man out" (Pond 1987:p63) and Pond's own words emphasise the point even more on the next page: "But however you compare them, Homo is clearly the odd man out. In proportion to body mass, we have at least 10 times as many adipoctyes as expected from this comparison with wild and captive mammals. Humans easily surpass such notorious fatties as badgers, bears, pigs and camels and are rivalled only by hedgehogs and fin whales, in their deviation from the general trend, indicated by the regression in that figure." Pond (1987:p64).

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.

2) Morgan 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.
Did she misunderstand it? I don't think so. Morgan wrote "Fat does not function in the same way in different species. When a laboratory rat puts on weight its adipocytes (fate cells) increase in size but the number of them does not change. In primates, however (including humans), the adipocytes tend to be smaller, but their number can be increased." (Morgan 1997:p96) This seems to me to be exactly what Pond had been arguing so, once again, one is left wondering why Moore would go to the trouble to make the point. You're left with the only conclusion possible that it was another misrepresentation aimed at nothing less than a character assassination.

3) Pond 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 statement.
But did she? Moore again gives no citation to this sort of claim but I scanned through all her books since Pond's article to see if I could find anything like it. In the latest book she reproduced the actual chart (Morgan 1997:p94) which Pond was describing, with the caption in full which included the words "Humans are rivalled only by the hedgehogs and fin whales in their deviation from the general trend." As to Moore's exact claim - that Morgan only mentioned the small adipocyte size of fin whales I found no trace of that in any of her books. Perhaps I just missed it but considering the tone of her treatment of this subject, I doubt she'd be trying to win cheap points on this matter.

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.
Indeed she did. Pond is very clear in her opposition to the AAH explanation for fat. Although it's true that Morgan could have been a little more "up front" in telling her readers that fact, it did not amount to any attempt to imply that she was on her side.  She did actually introduced a five page section on Caroline Pond by saying: "I felt that the anomalous thick layer of subcutaneous fat was one of the strongest pieces of evidence in its [AAH] favour. I still believe that - but the claim has by no means gone unchallenged...."
Perhaps what is more interesting here are Pond's arguments against the AAH. In the side-bar of her New Scientist article 'Fat and Figures' entitled "Not an aquatic ape - just an exceptionally fat mammal" she does list several objections to the hypothesis, none of which are new and unique and most seem to be based on the familiar exaggerated 

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.
 In fact Pond, like Moore, appears to have carved out a bit of niche for herself in opposing the AAH. Just a few months after the New Scientist 'Fat and Figures' article she wrote another purely about the AAH, entitled 'The great ape debate' (Pond 1987b). And she was one of the most articulate authors arguing against the AAH in the Valkenberg Symposium. Her message is quite consistent: That the distribution of fat in humans is no different from any other terrestrial mammal and rather different from aquatic mammals. She makes the case that the 'subcutaneous' layer of fat in humans is an illusion borne out of the simple fact that humans so fat that typical mammalian fat depots have become run together to form a continuous layer. She is quite up front that humans are significantly fatter than other mammals and primates but somehow never quite gets round to putting forward a good hypothesis of her own as to why that might be.
The best we tend to get is that the rather important differences between the two sexes in this area tends to suggest that it might be something to do with sexual selection. This argument could well have an element of truth but it doesn't really explain why even quite lean tend to on fatter than the most obese captive primates.
Pond is very good at articulating the view that human adipose tissue would not be very functional as a thermoregulatory device in water but has not, to my knowledge, ever made the case as to why it would not be very useful as a buoyancy aide for hominids that regularly swam.

5) Morgan claimed that fat was an adaptation for insulation in an aquatic environment again contradicting Pond.
Even assuming that there is some truth in this claim (Moore again fails to give a specific citation) it is doubtful that Morgan had ever argued that this was the only reason. Certainly she has argued for other factors too: "Surface feeders tend to have very thick layers of fat which contribute to their buoyancy" Morgan (1997:p97). Moore makes no mention of that and, incidentally, neither does Pond. At least not in her 1987 New Scientist paper.

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.

6) Pond 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.
Nobody could dispute that fat had a major role in food storage but that explanation does not start to answer the question why humans would, therefore need to have so much more fat than similar sized mammals. One could argue that babies the need fat for the extra brain growth and women need the extra fat to help feed their babies but why would adult men need to have so much fat? It certainly does not fit well with the prevailing models of early hominids that had ever increasing ranges through which they wandered with ever increasing efficiency.
Again the point about buoyancy in a water-side dwelling animal appears to have been neglected.

7) Pond 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 selection.
The point here, it is argued, is that where there are differences between the sexes in a given attribute, then explanations due to sexual selection should be considered, and in terms of human fat, there are significant differences between the sexes, whereas in aquatic species there is very little difference between the sexes.
This is true enough and sexual selection  may well explain a good deal of the differences between the adipose tissue levels in men and women. But it does not answer the question 'why do human infants have so much more fat than chimpanzees?' or why should even the leanest men still have generally more fat than the fattest primates?
As with many areas in this debate, it would be very easy and helpful to accommodate some moderate aquaticism in any model that explains our high levels of fat. A water-side lifestyle requiring some swimming and diving would be likely to favour the selection of those traits that increased buoyancy. It is a complementary model to the other ideas, not a contradictory one. And yet, it seems, it must be resisted.

8) The life history of fat development in humans and aquatics is very different.
Aquatic mammals gain fat whilst they are very young until it reaches the level of their parents at which point it levels off. In humans we start off fairly fat but then levels drop to the leanest levels in our lives until another spurt at adolescence, which is radically different between the two sexes.

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.

Pond has 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)
Yet, it seems, when it comes to more aquatic uses of fat she, like Moore, is assuming that for fat to be any use to an animal at all in water, it must be exactly analogous to the whale's use - in other words, for thermoregulation.
Could this be another case of double standards?

9) Polar 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.
Moore says Pond has studied a lot about bears and he claims "This is just one of many scientific tests of the AAT which it fails."
Moore doesn't give a citation to back this claim up which is a shame because it could be a crucial piece of evidence against the AAH.
I did search the web and found this quotes...

"The polar 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.
Sources: San Diego Zoo/Wild Animal Park ZooNooz, February 1996; Polar Bears by Nikita Ovsyanikov (Voyageur Press, Stillwater, Minnesota, 1996"

"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.

10) According to Pond, fat isn't a particularly good insulator anyway.
This assumes that the AAH argues that thermoregulation is the only benefit of the fat layer, which it doesn't.
Once again the buoyancy has been ignored.

11) The issue of high human infant fat is explained by the large human brain as pointed out by Jane Lancaster.
Moore provides no citation for this claim either but it is a familiar argument. The large infant human brain would appear to be the only distinguishing feature between humans and chimpanzees, other than our increased abilities in water,  which may explain the need for greater fat being laid down in utero, but it begs the question: Was the large brain a cause or a consequence of that fat?
In any case, having a large infant brain is by no means a contradictory argument to the need for increased buoyancy, in fact as I have argued elsewhere, it could even be seen to be part of the same phenomenon.

12) Measuring fat in modern humans probably does not give an accurate measure of the level in the rudimentary tool-using populations of 5 Ma.
This is true and Moore, once again, makes a reasonable point in countering the original Hardy/Morgan hypothesis that there was a distinct 'aquatic phase' that preceded the speciation of Homo sapiens. The level of adipose tissues in early hominids will probably never be known and therefore it would seem to be of little value to speculate about it. The fact that humans today have clearly  an in-built tendency and capacity to lay down more fat than our closest primate relatives suggests that there is something to be explained here. Pond's argument against the aquatic explanation seems to be based too much on the idea that it evolved for analogous reasons as did the adipose tissue of whales - for thermoregulation - and all but ignored the more likely benefit for a slightly aquatic waterside dwelling hominid, increased buoyancy. Pond doesn't really promote an alternative argument she favours herself either other than some hand-waving about sexual selection.

Moore's summary
Having posed these problems to the AAH proponents, Moore provides a selection of 17 quotations, all from Caroline Pond to back them up. Before doing that though,  he summarises the case against the AAH argument for fat by suggesting that there is no big deal here, as the ability to get fat is shared, he claims, with our primate relatives. Moore makes his point clear by stating: "Why this is a shock to AATers is, frankly, a mystery to me. Why does our species get fat? It seems the answer to that is because we can." He goes on to explain that fat is generally a good thing for any animal - "It gets you by in times of little food, and provides a cushion, so to speak, in times of illness" but that it can be a hindrance when needing to escape predators. Moore answers this by suggesting that predators "have been a relatively minor problem for humans since we developed the controlled use of fire and effective weapons around a million years ago."
This, at least, is a plausible alternative model to the AAH for our increased fat content and he gives a solid example to back this argument. Comparing two groups of reindeer, one, isolated on an island without predators. He says the isolated one has been 'free' to get fatter and slower due to lack of predation. Moore quotes Pond when she wrote: "Norwegian mainland reindeer would probably like to get fat too, but this would make them inefficient runners, a luxury they cannot afford."
The Open University Alumni On-line Community, Open Eye On-line, "Reindeer" December 2000

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? 

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