17 The Non-Aquatic Ape: The Aquatic Ape Theory and the Evolution of Human Drowning and Swimming
Jan Wind (19 Pages)

SUMMARY

From an analysis of the evolutionary processes that have led to the features that have diminished humans' adaptation for survival in the water, it appears that from a traditionally biological point of view we are indeed, like the apes, poorly adapted. However, the percentage of humans that actually die from drowning is relatively low - the result of other, counteracting, adaptations namely, our cognitive and manual abilities. A central question of the Aquatic Ape Theory debate, not hitherto addressed, is therefore: did the aquatic ape already possess these abilities, including those of transferring to conspecifics, especially offspring, the necessary knowledge? Indications from comparative morphology, physiology and ethology, and from paleoanthropology, appear to offer a negative answer to this question. The analysis, therefore, does not support the AAT.

INTRODUCTION
Attempt to test the AAT with data.

MAN AND WATER: THE PARADOX
"Remarkably, most humans and all apes swim less well and drown more readily than virtually all other animals, including monkeys." p 263

LIFE AND WATER
All life comes from water and contain it. Human inability in water therefore needs some explaining.

LOSS OF WATER ADAPTATION
How could such an adaptation be lost? Lack of exposure to the threat of drowning. Perhaps through intelligence - using floating devices to avoid the need for it.

BUOYANCY
Density of mammals varies. e.g. Women 0.96 - 1.06, Men 1.021 - 1.097. Hog 1.018, Cat 1,031 - 1.097.

Breathing in makes a big difference.

BREATHING
Difficult when not buoyant. Need to get air is more easily fulfilled on ones back.

ASPIRATION, HYPOTHERMIA AND OSMOLARITY
Inhalation of water is more likely in humans than our ancestors for 4 reasons:
1) Mouth breathing -gasping for more air, more difficult to keep above surface than nostrils.
2) Gap between choanae(?) and larangeal entrance.
3) BMR higher than pre-mammalian ancestors.
4) Cooling of body cause impairment of brain metabolism.

Cold water kills as does salt water.

LOCOMOTION
Humans in water for the first time tend to panic. With trial and error this can be avoided and swimming strokes be learned. The plasticity of our behaviour facilitates this as does the accumulation of knowledge and experience, language etc. and our extremely moveable shoulder joints from our arboreal past.

HUMAN BEHAVIOUR
Hyperventilating before diving can be a killer because it lowers the CO2 level in the blood delaying the onset of natural need to rise to the surface.

EVIDENCE FROM THE APES?
Apes are as bad as us except that 1)Hair cover probably makes them more buoyant. 2) hypothermia less probable because of their hot habitat. 3) behaviour involves less drowning situation and 4) denser than humans. But little evidence as it is unethical to test.

OCEANIC DESIRES
Probably due to early memories of bathing and need for escapism.

THE AAT AND THE SWIMMING BABIES
AAT proposes human infants swim.
1) Phylogeny thru ontogeny argument does not hold much water.
2) Infants don't swim very well. They need to have their head supported. They drown in shallow tubs, Explained more by babies horizontal posture and lower density.

CONCLUSION
Cultural v biological. Nurture v nature. In human evolution there has been an increase in nurture and a decrease in nature.

COUNTER-ARGUMENTS

Jan Wind makes some interesting points. I am particularly interested about his assertion that humans and apes share about the same level of incompetence in water. If this were true it would surely strongly argue against the AAH.

However Wind did not address the distinctive hydrophobia of chimpanzees and bonobos and make any comparison with humans - particularly infants, which cannot be exposed to any culture or nurture - his main argument.

That to me is the biggest weakness in his argument. Human babies are 15% fat, hence relatively buoyant as he admits. There is a very large difference between humans and chimps in this regard and it needs an explanation.

The lack of buoyancy in human adults is surprising, but could explain why we have such powerful voluntary control over our breathing.

I was also taken by the idea that technology and use of floating aids would clearly, paradoxically make us less well adapted to water. As hominid technology improved over the last 2 my this would probably have been a factor in our swimming abilities and might even explain why we are not much better in water than AAH opponents would like to predict.