Aquatic ape hypothesis

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The aquatic ape hypothesis (AAH), sometimes referred to as the aquatic ape theory, asserts that wading, swimming and diving for food exerted a strong evolutionary effect on the ancestors of the genus Homo and is in part responsible for the split between the common ancestors of humans and other great apes. The AAH attempts to explain the large number of physical differences between humans and other apes, such as lack of body hair, larger brains and upright posture, in terms of the methods of feeding and types of food of early hominids living in coastal and river regions.

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[edit] Hypotheses

As compared to their nearest living relatives, the great apes, humans exhibit many significant differences in anatomy, including bipedalism,[1] hairless skin,[2] increased subcutaneous fat[3], greatly expanded brain size, a hooded nose which prevents water from entering the nostrils[4], and greasy skin with an abundance of sebaceous glands, which can be interpreted as a waterproofing device[5] There are several variants on the broad theme that early or proto-humans lived in close proximity to water, gathering much of their food in or near shallow bodies of water and developing and adapting new modes of locomotion in order to move and gather food (possibly including wading,[1] swimming[6] and diving[3]). Proponents have disagreed on the relative importance of fresh water[7] versus coastal or brackish water[8] habitats. Although the earliest proponents argued for an early (Miocene, ca 6Ma) timescale[3] most now favour the view that the critical period of close association with waterside habitats was much later, since (or just before) the time of the genus Homo (ca 2.5 Ma.)[9]

[edit] History

Prior to 546 B.C., the Milesian philosopher Anaximander proposed that mankind had sprung from an aquatic species of animal. He thought that the extended infancy of humans could not have originally permitted survival as a land-based species. This idea was based on elemental forces of mutation as opposed to natural selection.

The German biologist Max Westenhõfer was perhaps the first to publish the idea in an evolutionary context, introducing it by writing "The postulation of an aquatic mode of life during an early stage of human evolution is a tenable hypothesis, for which further inquiry may produce additional supporting evidence" [10] but it was the marine biologist Sir Alister Hardy who is more commonly associated with the origins of the idea when he announced his thoughts in a speech to the British sub-aqua club in Brighton on 5th March 1960.

News of the speech generated immediate controversy in the field of paleoanthropology and Hardy quickly followed up by publishing two articles in the scientific magazine "New Scientist".[3] In the article Hardy defined his idea: "My thesis is that a branch of this primitive ape-stock was forced by competition from life in the trees to feed on the sea-shores and to hunt for food, shell fish, sea-urchins etc., in the shallow waters off the coast. I suppose that they were forced into the water just as we have seen happen in so many other groups of terrestrial animals. I am imagining this happening in the warmer parts of the world, in the tropical seas where Man could stand being in the water for relatively long periods, that is, several hours at a stretch." Hardy (1960:642)[3] Despite receiving some positive feedback in the letters pages of New Scientist in the weeks that followed and strong backing from a professor of geography[11] , the idea was largely ignored by the scientific community.

In 1967, the idea was referred to positively in "The Naked Ape", a book by Desmond Morris in which can be found the first use of the term "aquatic ape" (Morris 1967:29).[12]

The early television playwright and later feminist writer Elaine Morgan read about the idea in Morris' book and was struck by its potential explanatory power. She developed and promoted it over the next thirty years, publishing six books on the subject.[13][2][14][15][16][17]

Several other proponents have published work in favour of the aquatic ape hypothesis during this time including the physician Marc Verhaegen[9], neurochemists Michael Crawford[4] and Stephen Cunnane[8], and ecologist Derek Ellis[7].

[edit] Reception by Academia

In 1991 a symposium was held in Valkenburg, Holland titled "Aquatic Ape: Fact or fiction?" and the proceedings published in Roede et al (1991)[18]. The chief editor Vernon Reynolds, although having marginally rejected the hypothesis, concluded "overall, it will be clear that I do not think it would be correct to designate our early hominid ancestors as ‘aquatic’. But at the same time there does seem to be evidence that not only did they take to the water from time to time but that the water (and by this I mean inland lakes and rivers) was a habitat that provided enough extra food to count as an agency for selection. As a result, we humans today have the ability to learn to swim without too much difficulty, to dive, and to enjoy occasional recourse to the water" Reynolds (1991:340)[19].

Despite the ambiguity in the wording of this summary, and the fact that eleven of the twenty-two papers submitted were in favour of the hypothesis, it was largely assumed that it had been decisively rejected. The one paper (Langdon 1997)[20] published in a first class anthropological journal specifically about the subject clearly did so.

Although Roede et al (1991)[18], Langdon (1997)[20] and a few others[21] rejected strong forms of the aquatic ape hypothesis, assessing if there was an "aquatic ape", it remains open to debate whether milder forms, along the lines Hardy first proposed (i.e. "was man more aquatic in the past?"), have even yet been seriously considered in the literature.

The hypothesis and its variations have been largely ignored by mainstream paleoanthropology, although some papers have criticised aspects of it.[22][21][20][23][24] It has been suggested, for example, that a broad enough terrestrial diet would ensure sufficient access to docosahexaenoic acid that there is no requirement for high consumption of seafood and accordingly no reason to posit an aquatic phase in human evolution.[25]

[edit] See also

[edit] References

  1. ^ a b Niemitz, C (2002). "A Theory on the Evolution of the Habitual Orthograde Human Bipedalism - The "Amphibisce Generalistheorie"". Anthropologischer Anzeiger 60: 3-66. 
  2. ^ a b Morgan, Elaine (1982). The Aquatic Ape. Stein & Day Pub. ISBN 0-285-62509-8. 
  3. ^ a b c d e Hardy, A. (1960). "Was man more aquatic in the past". New Scientist 7: 642-645. 
  4. ^ a b Crawford, M et al (2000). "Evidence for the unique function of docosahexanoic acid (DHA) during the evolution of the modern hominid brain". Lipids 34: S39-S47. 
  5. ^ Kingdon, Jonathan. (2003) Lowly Origin Princeton University Press, 242
  6. ^ Patrick, John (1991). Human Respiratory Adaptations for Swimming and Diving. Souvenir Press. 0-285-63033 4. 
  7. ^ a b Ellis DV (1993). "Wetlands or aquatic ape? Availability of food resources". Nutrition and health 9 (3): 205–17. PMID 8183488. 
  8. ^ a b Cunnane SC, Plourde M, Stewart K, Crawford MA (2007). "Docosahexaenoic acid and shore-based diets in hominin encephalization: a rebuttal". Am. J. Hum. Biol. 19 (4): 578-81. doi:10.1002/ajhb.20673. PMID 17546620. 
  9. ^ a b Verhaegen, M.; Puech, P.F.; Munro, S. (2002). "Aquarboreal ancestors?" (pdf). Trends in Ecology & Evolution 17 (5): 212-217. doi:10.1016/S0169-5347(02)02490-4. 
  10. ^ Westenhõfer, M. (1942). Der Eigenweg des Menschen. Mannstaedt & Co. 
  11. ^ Sauer, C O. (1960). "Seashore - Primitive home of man?". Proceedings of the American Philosopical Society 106 (1): 41-47. 
  12. ^ Morris, Desmond (1967). The Naked Ape. McGraw-Hill. ISBN 0 09 948201 0. 
  13. ^ Morgan, Elaine (1972). The Descent of Woman. Souvenir Press. ISBN 0 285 62700 7. 
  14. ^ Morgan, Elaine (1990). The Scars of Evolution. Souvenir Press. ISBN 0-285-62996-4. 
  15. ^ Morgan, Elaine (1994). The Descent of the child. Souvenir Press. ISBN 0-285-63377-5. 
  16. ^ Morgan, Elaine (1997). The Aquatic Ape Hypothesis. Penguin. 
  17. ^ Morgan, Elaine (2008). The Naked Darwinist. Eildon Press. ISBN 0-9525620-30. 
  18. ^ a b Roede, Matilde (1991). Aquatic Ape: Fact of Fiction: Proceedings from the Valkenburg Conference. Souvenir Press. ISBN 0 285 63033 4. 
  19. ^ Reynolds, Vernon (1991). Cold and Watery? Hot and Dusty? Our Ancestral Environment and Our Ancestors Themselves: an Overview (in Roede et al 1991). Souvenir Press. ISBN 0 285 63033 4. 
  20. ^ a b c Langdon JH (1997). "Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis". J. Hum. Evol. 33 (4): 479–94. doi:10.1006/jhev.1997.0146. PMID 9361254. 
  21. ^ a b Lowenstein, J.M.; Zihlman, A.L. (1980). "The Wading Ape-A Watered-Down Version of Human Evolution". Oceans 17: 3-6. 
  22. ^ MacLarnon, A.M.; Hewitt, G.P. (1999). "The evolution of human speech: The role of enhanced breathing control". American Journal of Physical Anthropology 109 (3): 341-363. doi:10.1002/(SICI)1096-8644(199907)109:3%3C341::AID-AJPA5%3E3.3.CO%3B2-U. 
  23. ^ Pagel, Mark (2003). "A naked ape would have fewer parasites". Proceedings of the Royal Society B: Biological Sciences 270 (0, 07 Aug 2003): S117. doi:10.1098/rsbl.2003.0041.. 
  24. ^ Jablonski, N (2006). Skin: a natural history. University of California Press. ISBN 0520242815. 
  25. ^ Carlson BA, Kingston JD (2007). "Docosahexaenoic acid biosynthesis and dietary contingency: Encephalization without aquatic constraint". Am. J. Hum. Biol. 19 (4): 585-8. doi:10.1002/ajhb.20683. PMID 17546613. 

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