Summary
AAT evaluated according to epistemological criteria and explanative value is compared with that of what AAT proponents call the savannah theory. Fossils reviewed for strictest 'functional' explanations. Develop some testable hypotheses about locomotor behaviour of presumed aquatic ancestors, something not so far proposed by AAT advocates. The morphological adaptations advantageous for some possible aquatic forms of locomotion do not exist.

We find that the AAT:
does not explain more findings than do the more trad ideas does not allow a more complete integration of accepted but unassociated facts does not contain fewer contradictions, nor leave fewer gaps does not allow more parsimonious explanations does not allow for more precise or more correct predictions of new findings does not yield hypotheses that can be tested in a more reliable , simpler or more convincing way that those deduced within the framework of the Savannah Theory. In fact the weakest point of the new theory seems to be that its proponents do not develop hypothetical explanations that can be tested on the basis of known natural laws, or even on the basis of empirically well established rules.

Brief Notes

Introduction
AAT offers a different explanation of human traits.

"Scientific seriousness demands an impartial judgment on the value of both theories" p 143 "This is what is attempted in this chapter."

Evaluated on these criteria...
1. Explanative value. 'able to explain more findings'.
2. Iintegrative value - 'allows for more complete integration of commonly accepted but formerly unassociated facts'.
3. Extension and absence of contradiction- a good theory does not leave gaps or imply contradictions.
4.  Parsimony - less complicated.
5. Prognostic value - superior in ability to make correct predictions of new findings.
6. Testability - to judge the prognostic value of a theory it must be possible to deduce testable hypotheses.
7. Stimulus value - a good theory should stimulate new approaches and research projects.

Survey of the Fossil Record
A summary of orthodox hominid evolutionary history.

p 146 "The environment in which the earliest of these evolutionary processes took place was according to paleo-ecological research something between woodland and savannah with gallery forests along rivers and freshwater lakes." and "There are no known fossil documents to support the assumption that seashores were the habitats of these forms."

A Selection of Hominoid Characters that can be explained functionally
General Remarks on functional explanations of morphological characters

"It is purely speculative to create, as do the AAT proponents, a system of presumed functional needs believed to be advantageous under hypothetical ecological conditions which have perhaps never existed among our ancestors." p146.

Concentrate on dentition, skull shape, trunk shape, pelvis, hindlimbs, feet, fingers and toes (in other words, it seems, everything apart from the spine.) Mechanical (functional) roles versus biological roles.

Miocene Apes
Proconsul lived in trees. (We knew that)

Australopithecines
Discussion on dentition. Reference to "The most intriguing trait, the relatively large brain" p148 is a bit puzzling. Encephalisation happened much later.

Then (p153) says that this line of reasoning (about dental changes) does not support that they were scavengers or hunters. "It would seem attractive (although it is not attempted here) to fit our argument into a scenario of hominids exploiting marine, coastal or benthic resources."

Head size increase and orthograde posture go together. Moving head towards centre of gravity makes sense in terms of this. In depth discussion of a'pith postcranium. Claiming that this shows a terrestrial specialisation for bipedalism.

p156 "A lot of 'reasons' for the evolution of upright posture and locomotion in terms of biological role have been proposed: ... To these we can hardly contribute anything new."

Homo erectus & Neanderthal man
"Between a'pith and H erectus important evolutionary changes took place. The brain enlarged from less than 600 cm3 to at least 800 and up to 1200cm3" p 161  - Fire. (A page not relevant to this debate.)

What new insights does the AAT offer?

In contrast to most pa, the proponents of the AAT have neither attempted to clarify the chronology of the known fossil documents nor to interpret them in terms of their differences and similarities." p 162. "Focus on explanation of modern man's peculiarities as compared to modern apes and other mammals."

AAT features -
1) some not at all peculiar to man and 2) those which can be explained more satisfactorily within the framework of conventional ideas.

Type 1
Low hair density is also found among modern large apes. Great apes have 300-500 hairs/cm2 cf lesser apes 2000-3000.Sweat glands - see Wheeler. sc fat see Pond.

Type 2
Bipedalism - primates have a tendency to do it anyway although the exact biological reasons is not understood. Perhaps it could be to do with the promising new approach offered by wheeler (Thermoreg.)

Upright posture might also explain diving reflex as trunk is kept in equilibrium at the invertebral discs not only by muscles contractions but also by making use of the 'pneu' formed by the intestines in the abdomen and thorax which are enclosed by the abdominal and thoracic wall muscles.

Questions to ask the AAT
1 When, in chronological framework would aquatic phase have occurred?
2 Which fossils in fact indicate an aquatic life?
3 Which traits must be present in an aquatic primate to fulfill its intermediate functional needs?

"Apparently they (AAT supporters) prefer raising questions to answering them." Since testable hypotheses proposed by AAT defenders are lacking, we have ourselves tried to pin down the possibilities that exist for an aquatic lifestyle.

1) The aquatic stage of hominid evolution took place along seashores. The ancestral hominids waded - searching for food, or avoiding predators - in shallow water (marsh waders).

2) Our aquatic ancestors lived in somewhat deeper waters, either swimming close to the surface or diving (shallow-water swimmers)

3) Our ancestors were active, endurant swimmers, able to move rapidly in deep waters (deep water divers.)

Marsh Wader Criticisms
Their first objection to the marsh wader is very good.

One would predict a marsh wader to have long, thin legs and reduce the emersion of the trunk. "Even partial immersion of the trunk, however, would greatly increase water resistance and make locomotion energetically very expensive and fleeing slow. In addition, the buoyancy of  the trunk would would relieve the vertical foot force to such an extent that wading became difficult because ground contact would be lost." p 165.

Also the femur: tibia ratio would be predicted to be < 1 so that the majority of the leg could be extracted from the water avoiding resistance in shallow water (up to knee depth).

"In addition soft substrates - as found frequently on the bottom of lakes or sea - favour a large are of support, which means long, wide feet."

These expected traits are not found in Humans.

Swimming
One would predict smaller limbs to reduce excessive rotation forces and enlarged hands and feet to act as paddles.

These have never been found in hominids.

"Webs between the fingers and toes, which increase the surface in the power stroke whilst being folded in the recovery stroke, may have occurred in fossil forms - we just cannot recognize them on the skeleton on the skeleton. But they exist also in the indisputably non-aquatic modern apes, where they are even better developed than in humans" ?

If bipedalism preceded swimming (as AAT proponents claim) the propulsion would be no problem diving. p 169.

Humans are not well adapted to swimming - limb length again.

The AAT claim that humans like wate is just a fashion - not true mre than 100 years ago. What about humans liking open grassland - parkland savannah?

Conclusion
AAT vague in several aspects
-    Absolute and relative dating
- Stresses some arbitrarily selected 'enigmatic' features of H sapiens and provides purely hypothetical explanations for them - without any attempt to give detailed, causal explanations for the origins of these traits.
- Because only biological roles and not mechanical  function AAT lacks precision - so absence of testable hypotheses and predictions deduced from them.
- AAT contains gaps -it is insufficiently integrated and not free from contradictions.
- Parsimony has to be questioned because of the lack of explanations for less conspicuous traits.
- AAT is not able to produce satisfying hypothesis that can be tested empirically.
- Does not provide us with a more complete understaning of the facts about human evolution than we have already got.
- Results of tests are in accordance with, or even support, the traditional paleoanthropological ideas which assume the evolution of hominids in a terrestrial, savvanh-like habitat.

"Although we feel attracted and, more so, challenged by some of the arguments from the AAT, we regret to conclude that we cannot offer any support to it. We do not agree that there is any need to postulate an aquatic phase in the evolution of man." p 170.

Counter-Arguments
1. They seem to make the common assumption of an exclusively marine habitat - from Hardy's original paper. They admit that Riverside/Lakes were a big part of the story but assumes that it means nothing.

2. Head size & orthograde posture argument. A. afarensis was bipedal long before encephalisation took place.

3. Their point about wading features is actually very good and constitutes a serious counter-argument to the wading origins model.

However, we have to bear in mind that the starting point for this wading ape is not a bird, already with thin legs - it is an arboreal primate.

Monkeys have relatively short hind limbs, tails, and very small feet.

When looked from this perspective A. afarensis looks more like a wading ape than if you compare it with a flamingo.

The point about the tibia: femur ratio is a difficulty. But if the depth of water was variable this is unlikely to have been a significant factor.

The flat pelvis and other pelvic-femoral traits found in A. afarensis indicate powerful adduction/abduction of the femur and have yet to be explained adequately using terrestrial or arboreal models.

4. Swimming criticisms.
Again - compared with what? With seals we are clearly maladapted to swimming but compared to monkeys, or even apes, we are rather excellent.

5. Fashion argument
American Indians? Klasies river mouth. Early Homo in Europe and Australia all have history of association with water.

Conclusion strong - but assume a 'strong' version of  AAT - with a 'phase' of distinct and marine aquatacism. This would appear false.

A riverine model would meet their criticisms better.