Scars of Evolution - Discussion

Two-part 'mini-series' on the Aquatic Ape Hypothesis, narrated by David Attenborough broadcast in April 2005

By Pauline Ross [pmross@ross-software.co.uk].

Critique of Jim Moore's Review of the 'Scars of Evolution' Program

On 12^th and 19^th April 2005, BBC Radio 4 broadcast two half-hour programs, entitled ‘Scars of Evolution’, about the Aquatic Ape Hypothesis. The first part described the AAH, its origins at the hands of Alister Hardy and its development in the several books on the subject written by Elaine Morgan, and the reaction of academics. The second part looked in more detail at evidence for the AAH. The program was narrated by David Attenborough.

Shortly afterwards, Jim Moore wrote a critique of these two programs, which he posted on his website at www.aquaticape.org. Moore’s comments fall into three categories:

-          Pointing out statements made in the program which he believes to be errors of fact;

-          Pointing out arguments made in the program which he believes to be errors of logic;

-          Sarcasm, ridicule, statements of his own opinion and experience and other subjective comments.

The following is a critique of Moore’s critique, and I shall address his comments in the same way, pointing out what I believe to be his errors of fact or logic. His subjective comments will be noted as they occur, but they obviously cannot be validated or refuted. If I am able to support his points, I shall say so. I make no attempt to judge the merits of the arguments put forward in the program as a whole; I only consider the points raised by Moore.

For convenience, I have broken his critique into short chunks which cover one topic. I have abbreviated Jim Moore to JM and David Attenborough to DA.

*** Long-distance swimming (“Attenborough starts off…”)

JM complains that DA fails to point out that long distance swimmers are highly trained athletes who “perform feats that ordinary humans do not, and cannot, do”; but on the contrary, DA says that his quoted swimmer, Lynn Cox, is “exceptionally gifted”.

*** Swimming vs running (“He then segues…”)

JM complains that DA mentions running speed (“our top speed is somewhat less than a rabbit”), but doesn’t mention swimming speed, which JM quotes as a maximum of 6 mph (JM: “pitifully slower than most swimming animals”). JM quotes the top running speed of humans at 15.5 mph. However, both these speeds are substantially slower than the top speeds of other species, both on land (eg cheetah, up to 60 mph) and in water (eg killer whale, up to 30 mph), so this means nothing.

JM then invokes an invalid comparison of his own – that in his twenties he could walk at 5 mph, almost as fast as an Olympic swimmer. This is irrelevant, however.

*** Sound bites (“Having set the stage…”)

The next two paragraphs are purely subjective, so I will ignore them.

*** The savannah hypothesis (“We’re at about…”)

The next section is interesting. It’s mostly subjective,  being JM’s assertions and some disparagement of various participants. However, since JM uses his own assertions as the *basis* for his criticism, it’s worth looking at more closely.

Initially, he says: “The idea of the ‘savanna hypothesis’ is important in discussions of the AAT/H because it’s the method by which AAT/H proponents inaccurately claim that paleoanthropologists use the same sort of environmental determinism that they use.” However, it is Leslie Aiello (not an AAH proponent) who introduces and describes the savanna hypothesis in the program JM is critiquing, so this comment is irrelevant.

Then JM criticises DA for his description of “the basic account of early humans most commonly told in schools”, involving hunting apes, etc. JM feels he should have included the work of women such as Rowell, Goodall, Linton, Tanner, Zihlman, Vrba and Behrensmeyer “who changed this way of thinking”. Of course, editorial decisions about how much detail to include are very subjective; this was, after all, a short program aimed at a general audience. DA obviously can’t name every influence, but he does say that the story was “a bit oversimplified”, which makes clear that the Mighty Hunter was not the whole story.

JM then brings up the definition of ‘savanna’: “… the talk was of a mosaic savanna woodland – although many people think of savanna as meaning a treeless plain, and Morgan and other AAT/H proponents have encouraged this belief, anthropologists know differently.” Once again, JM invokes “AAT/H proponents”, and once again this is irrelevant.

Here is JM’s preferred definition of savanna:

“In central and southern Africa savanna is used for open deciduous woodlands, including those locally known as miombo, that are composed of fairly tall, mesophyllous trees and a well defined grass stratum, for parklike vegetation comprising grasslands studded with microphyllous trees of low to medium height, for grasslands with scattered clumps of trees or bushes, for treeless grasslands of tall perennial mesophytic grasses and of short annual grasses mixed with perennial grasses with narrow rolled leaves, and for open forms of vegetation composed of scattered low growing microphyllous trees and shrubs and a ground layer of perennial and annual grasses. The term bushveld is used locally for the parklike forms of savanna which together with the low tree and shrub forms are regarded as the most typical savannas.” [1]

Well, that’s quite a mouthful, but it’s clear that all the described forms contain grass, while all but one contain some trees. JM’s short form of this (“mosaic savanna woodland”) makes no explicit mention of grass, emphasises the trees and introduces a new term, mosaic, not mentioned or implied by the definition.

Here’s a shorter definition:

“subtropical or tropical grassland with scattered shrubs and trees and a pronounced dry season…” [2]

This one emphasises the grass, reduces the importance of the trees and (again) has no mention of mosaic.

To return to JM’s criticism, that “…the talk was of a mosaic savanna woodland […] Attenborough either doesn’t know this or doesn’t want to mention it…”, let’s quote Leslie Aiello again from the program: “What many people forget is that there is a huge spectrum of environmental types in Africa. It’s not just totally open savannah like the Serengeti, and totally closed rainforest. There seems to be a mosaic or mixed environment.” So the mosaic aspect *was* covered by the program. 

As to whether DA uses an accurate description of savanna (“wide rolling grasslands”, “open plain”, “open savanna grasslands”), all his references to plains and grasslands are in the context of historical views of human evolution, now defunct, which Leslie Aiello also described (“…you had a rather simple idea that early humans lived in open country.”). And there really is no reason why DA should use JM’s preferred definition of savanna.

*** Back to square one (“Attenborough then plays…”)

Essentially opinion and rhetoric, so ignored.

*** Elaine Morgan (“Now we have the formal…”)

JM complains about Elaine Morgan’s claim of a “peculiar layer of fat tightly bonded to the skin that humans have and other primates lack”, and points out that this layer is seen in any primate which essentially overeats, naming Caroline Pond in support.

This is not true; Caroline Pond also said: “Only cetaceans, pinnipeds and a few species of carnivores and rodents normally have as much fat as ‘typical’ humans”;  “The average fatness of humans is much greater than that of monkeys” [3]; "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. ... The minimum fatness recorded for teenage girl athletes is 7%, and for men 5%. Thus most human beings are not only much fatter than most wild and captive mammals, but women and girls are consistently fatter than men and boys." [4]

*** Scientific reaction and being an outsider (“According to Morgan…”)

This whole section is largely subjective, as Morgan and others describe from their viewpoint the reaction to Hardy’s original idea and Morgan’s books (Daniel Dennett refers to the “irrational hostility she [Morgan] engenders”), and JM counters with his own point of view (“Apparently not having your poorly thought out and supported idea immediately accepted is equivalent to being ‘barred’.”). Not much to analyse here, but JM does put in a couple of half-compliments; good to see a bit of balance.

*** Wegener (“Uh oh, it’s 25 minutes in…”)

As part of the discussion of Morgan as a scientific outsider, DA raises the matter of Wegener: "The reviewer was referring to the theory of Alfred Wegener that the continents of the earth are drifting apart.  As a meteorologist Wegener was also a classic outsider and his theory was roundly ridiculed and rejected by geologists for over 30 years.  But when the submarine research in the 1960s finely proved that the Atlantic sea floor really was spreading apart, hostility faded and Wegener's Plate Tectonics became the accepted paradigm."

JM claims this is inaccurate, but I have been unable to find any reference which is significantly different from DA’s description.

JM further claims that when DA talks about “Wegener’s Plate Tectonics” he is “using a rhetorical trick, either because he’s ignorant or he’s deliberately trying to make a connection in people’s minds to make Wegener’s opponents seem, well, irrational, just as he’s trying to make Hardy and Morgan’s opponents seem irrational.” JM says the distinction between plate tectonics and continental drift is an important one, but this is his opinion. In the context of a radio program for a general audience, it is *not* important, and I think DA’s short summary is as accurate as you can get in 3 sentences.

In addition, JM is himself guilty of using false logic here (“…either […] he’s ignorant or he’s deliberately trying…”). Well, no, there are plenty of other possibilities. Far more likely, in my view, that DA knows perfectly well the distinction between continental drift and plate tectonics (the effect and the mechanism), but chooses not to confuse his audience with the details. Or he considers it irrelevant (as I do). Or he simply didn’t have time to be more precise.

The rest of this section is largely rhetoric (“… when the ‘evidence’ used to support [AAH] is largely false, some people may consider this important. Not Attenborough, apparently, but some people.”).

*** Start of the second program (“Okay, this is good. “)

More rhetoric (“dubious and misleading research offered as evidence”), and a promise of logical fallacies to be uncovered.

*** Paradigm shift and savanna grasslands (“First we have some hyperbole…”)

DA: “For forty or more years the accepted crucible of humanity was the open savanna grassland of Africa and the aquatic alternative was ridiculed. Then, really since the early 90s the consensus began to fall apart. Why? What new evidence has come to the fore in the last ten or so years to cause such a paradigm shift to drive the anthropological mainstream off the savanna and, with a certain amount of pushing and shoving, and cautious hesitation, down to the water's edge?"

JM goes into full rhetorical mode here, first about “paradigm shift” (“… brace yourself for BS. […] the world of fringe science, and of pseudoscience, is where you here it used most.”) and a gratuitous comparison with creationists, then about “savanna grassland”, which according to him should be “mixed woodland or savanna mosaic”. This is entirely JM’s assertion (and see the savanna discussion previously).

*** Relative brain size and EQ (“Two minutes in and…”)

Michael Crawford talks about savanna mammals losing relative brain size as they evolved bigger, whereas human brain grew 3-fold. “When one compares the land-based with this universal collapse of brain size, with what goes on in the marine system I mean you’ve got the dolphin which is about the same body weight as a zebra; the zebra has about 360-370 g of brain in its head; the dolphin’s got 1.8 kg.”

JM is outraged: “Yikes. This is what happens when you have people who A) have no background in the study of evolution, and B) don't do their homework on it before they start C) making statements on subjects they know little or nothing about. Or, possibly, he does know what's wrong with what he's saying and is deliberately misleading others about it, which would actually be worse.”

Again, JM uses the ‘ignorance or … something worse’ false dichotomy. He then talks at great length about encephalisation quotients (EQ), which takes absolute measures of brain and body size and converts them via a formula to a single number for each species, which can then be used to compare brain sizes between different species. The standard formula for EQ is:

EQ = (brain weight) / ((constant C) * ((body weight) ^ (constant r)))

where r is an empirically determined value, which has been quoted as anything from 0.56 to 0.7, but is generally taken to be around 0.66, and C is usually quoted as 0.12 for birds and mammals, a number which produces an EQ of around 1 for the cat, arbitrarily taken as the ‘typical’ mammal. Species with EQs greater than 1 are said to be ‘more encephalised’ than would be expected for their body weight, those with EQs less than 1 are said to be ‘less encephalised’ than expected.

The really useful part about EQ is that it produces a list of numbers with humans at the top (8.38 with the given constants), then dolphins, the higher primates and, below 1, rodents and small mammals, and this fits very nicely with our ideas of ‘intelligence’ in the animal kingdom. It is not at all evident, however, whether brain and body size do predictably co-vary (there are many EQ anomalies), or exactly what EQ is measuring, if anything.

It is not quite clear, but JM appears to have two complaints: firstly, that Crawford should use EQ rather than absolute brain/body sizes; and secondly, that Crawford is “comparing apples with oranges” and picking his examples rather carefully (“One might say suspiciously carefully”).

On the first point (and it’s not clear whether JM is really saying that EQ is a better measure or not), Crawford has already discounted the body size angle by choosing a savanna species and an aquatic species with the same body weight, so their EQs (0.85 for the zebra, and 4.277 for the dolphin, taking the weight of a Plains Zebra, 235 kg, for both) show the same ratio as the absolute brain sizes (5:1). So in this case, it makes no difference whether absolute brain size or EQ is used for comparison.

On the second point, JM points out that predators and animals which live in small, highly interactive social groups (such as dolphins) tend to have higher than expected EQs, while prey species (such as zebras) typically have below-average EQs. He asks why, if Crawford proposes aquaticism as a reason for large brains, he didn’t choose a manatee (EQ 0.3 [5]) or, if it is to do with a seafood diet, he didn’t choose a fish-eater like a seal (ringed seal EQ 1.4 [5]).

These are good points which perhaps emphasize that EQ (and absolute brain and body sizes for that matter) may not be reliable guides to intelligence. It seems quite likely that body size may be affected by lifestyle far more than brain size (so that highly arboreal (eg most primates) or fast-moving predator (eg dolphins) species may require a light body (thus making them appear more encephalised), while slow-moving, highly aquatic species such as manatees can afford a much larger body (thus making them appear less encephalised).

The classic example is breeds of domesticated dogs, which have brains of quite similar size while having very differently sized bodies. The chihuahua is much more encephalised than the great dane; does anyone think this represents greater intelligence in the chihuahua? In fact, there is good evidence to suggest that the high EQs in primates is simply due to selection for smaller body size [6].

In summary, it is my opinion that neither absolute brain/body sizes nor EQ is a particularly useful or meaningful point of comparison between species. JM is half right in noting some of the problems, but his own examples (manatee/ringed seal) are no better or worse than Crawford’s (zebra/dolphin).

*** Omega-3 fats (“There’s the mention…”)

JM accepts that omega-3 fats and iodine are needed for normal brain development. He then complains at Crawford’s assertion that the only place enough of these are available is at the seashore, and says that they are available even in savannah conditions.

It is possibly true that in theory modern humans can find enough of these nutrients away from the sea, although the numbers with deficiency illnesses like goitre suggest it is marginal. So JM is half right, although I do wonder whether an environment with ‘just enough’ iodine and omega-3 is sufficient to drive the enlargement of the human brain, a process taking several million years. It seems more plausible in an environment with great abundance.

JM then protests at DA wondering why savanna predators like big cats didn’t develop big brains, if it could be done by eating the bone marrow and brains of prey. He points out that species develop just the size of brain they need and no more, regardless of the amount of brain-specific nutrients available. Apart from a gratuitous creationist slur against DA, JM is quite right on this one.

*** Land-based diet (“Attenborough goes on…”)

Still talking about omega-3 fats and iodine, DA says: “…if we switch to a new land-based diet that’s poor in those nutrients brain function will suffer…”

JM quibbles over this, because the qualifier “that’s poor in those nutrients” makes the statement true for any environment. He dislikes the suggestion that a land-based diet will *necessarily* be poor in those nutrients.

This is valid, but irrelevant, since it is quite clear that the marine food chain is indeed far more abundant in these nutrients than a land-based one (JM skips quickly over the program’s evidence for this – some 740 million people in inland populations suffer from iodine deficiency worldwide, according to the World Health Organisation).

*** The hobbit and anthropoid apes (“Attenborough mentions…”)

JM dislikes the mention of the small hominid found on Flores recently, apparently introduced for the sole purpose of leading the listener into the Homo erectus remains found there 850 kya. That’s a subjective issue, but it does tie the program’s discussion to more topical news.

The earlier Flores hominids may have got there by swimming, on a raft or by drifting across accidentally (as other species have done), but Elaine Morgan points out that if it were a raft or swimming, they were clearly “very confident in the water already”.

JM takes issue with Morgan’s use of the term “anthropoid apes” to describe the Homo erectus specimens on Flores. Again, given the likely level of the audience, this is not an unreasonable term to use.

*** Breath-holding (“On to the subject of holding one’s breath…”)

DA: “…in land mammals, including our primate cousins the chimps and gorillas, breathing is entirely involuntary; you can’t get a chimp to hold his breath. Breathing is as unconscious as the beat of its heart.”

JM doesn’t know about the apes, but says that some land mammals can hold their breath, for example, dogs (his website also says that some monkeys can do so), and that untrained dogs can hold their breath “somewhat longer” than untrained humans.

JM may possibly be right that other land mammals can hold their breath, but dogs are not a good example of any natural behaviour, having been domesticated intensively for millennia. It is common to ‘teach’ dogs to swim, by habituating them to water gradually and repeatedly, and undoubtedly they also learn to hold their breath during this process.

My suspicion is that many, possibly most, mammals can learn to hold their breath if exposed to the right conditions, so although JM is partially right, his supporting evidence is tenuous.

*** Swimming babies (“Now it’s on to…”)

JM starts by criticising DA for his remark: “Diving response and natural swimming abilities are displayed extremely early in the growth of the human infant. Indeed they are strongest at birth.”, which he describes as a “false fact”. It isn’t, of course. Since JM himself believes it to be a “universal mammalian response”, it must also be true of humans (and the radio program doesn’t suggest that it is unique or even unusual in humans).

JM further criticises DA for saying: “It seems extraordinary that humans, reputedly a land mammal, should find giving birth in water a perfectly natural thing to do.” I have to say that I also find it extraordinary that a primate species should find any benefit in giving birth in water, but this fairly subjective.

JM points out that every mammal infant has spent its gestation in a watery environment. Water birth has been in fashion in the west for several decades (and the program also gave examples of it in Indonesia and Russia), and the effects on both infant and mother have been very well researched, and the outcomes are better overall for both than with conventional western birth strategies. For the baby this might only be because of the prenatal environment, but it is suggestive that the outcome is also better for the mother (although it is possible that water birth is simply a more relaxing, less medicalised experience). I would say JM is partly right here.

*** Vernix caseosa (“Now we get into something interesting…”)

DA reports on a very recent finding that newborn harbour seals have a similar greasy coating to that found on newborn human infants.

JM’s only complaint here is that no one appears to have asked any detailed questions about this which might determine whether it really is evidence for an aquatic past in humans. This would be a fair point if it had been known for years, but it has only just come to light, so it’s hardly to be expected that any proper research has been done.

JM then makes some generalisations about “AAT/H proponents” which are subjective assertions.

*** Winding up (“Attenborough closes with the claim…”)

After a side-swipe at another mention of Wegener (“…the false story of Wegener they use.”), JM complains that DA has not raised any evidence for many of the features of the human anatomy he mentioned previously as suggestive of an aquatic past. Certainly the nakedness, sweating and bipedalism have not been discussed, so JM is right about this as far as it goes. On the other hand, DA did not suggest he would be introducing evidence for all these features. Once again, JM fails to allow for the shortness of the program. The points which have been raised were covered in a bit of detail, often with an opposing view, but there obviously wasn’t time to cover everything.

Summary and conclusions

In summary, I find only one of JM’s points wholly sustained, and 5 others partly sustained, by his evidence. The other criticisms he makes are either subjective or irrelevant. In addition, he himself makes 7 errors of fact and 2 errors of logic.

A major problem with his critique is that he makes no allowance for the format of the radio program, its length, and the likely audience. His comments would be more appropriate if he were reviewing a research paper, rather than a brief popular science radio program for a general audience.

Also, several times he criticises participants for not using his preferred definition or method. If he gives reasons for his preference, as he does with EQ, this is fine, but for ‘savanna’, there are many definitions and no general consensus about which to use, so there is no particular reason why anyone should use JM’s.

On a more general note, JM’s website (intended as a scientific critique of the Aquatic Ape Hypothesis) is a laudable effort, but in practice it is laced with subjective comments, many of them highly derogatory, such as suggesting that people are deliberately intending to mislead or ignoring contradictory evidence, when it is perfectly possible that they genuinely hold a different view. This detracts from the claim to be truly scientific. The site would also be more objective if it were updated with recent research – for instance, the page ridiculing the idea of an aquatic rhino ancestor should include the Clementz and Koch paper [7] which finds evidence for exactly that.

This critique was written by Pauline M Ross [pmross@ross-software.co.uk].

References:

[1] The Savannahs: Biogeography and Geobotany, by Monica M. Cole, 1986. Academic Press: London.

[2] The Cambridge Encyclopedia of Human Evolution, ed. Steve Jones et al, 1992, Cambridge University Press

[3] Adipose Tissue in Human Evolution, Caroline Pond in The Aquatic Ape: Fact or Fiction, 1991

[4] Fat and Figures, Caroline Pond. New Scientist Vol: ? (1987) Pages:62-66

[5] PT Schoenemann. An MRI Study of the Relationship Between Human Neuroanatomy and Behavioral Ability. Doctoral dissertation, 1997, UC Berkeley Dept of Anthropology. Figures based on Martin's [1981] original EQ formulation that has humans showing up at about 5.

[6] The Symbolic Species, by Terrence Deacon, 1997, The Penguin Press, London.

[7] Clementz, M T, Koch, P L, (2001). Differentiating aquatic mammal habitat and foraging ecology with stable isotopes in tooth enamel. Oecologia 129, 461-472