The Aquatic Ape?

• Appendix?? by Mike Rohrbach, 1/7/98
  
  

I've noticed a title, "The Scars of Evolution" by Elaine Morgan at a local bookstore. I ignored it, assuming the book to be a summary of our similarities to other primates. When someone posted the question, "Why the Appendix?," I decided that I had a good excuse to drop $13 on a factoid collection. I next parked with an orange juice at a mall table and started to read. And read and read .... the first time since forever that I did not postpone finishing a book.

Her argument is that something dramatic must have happened to push our attributes so far from other primates. Her "something" is an isolation of a group of our ancestors on a former island (Danakil Island, riding on its own micro tectonic plate) on the southern end of the Red Sea, about 7 MYA and in a primarily aquatic setting. She acknowledges her inspiration by Marc Verhaegen (1987) and bases her case on a mosaic of findings that do not fit into savanna models.

a) Bipedalism is of no adaptive advantage except in aquatic settings. Other primates also moved out onto the savannas but did not become bipeds. The only other primate to be bipedal happens to be in an aquatic setting in Asia.

b) Moving through water in an upright position does not put excessive pressures on our spines, apparently designed for quadrupeds.

c) Hairlessness is a significant disadvantage in warm climates. It is an advantage in aquatic settings.

d) We sweat through eccrine glands that pass salt directly from within our body. The only place in which salt disposal is an adaptation is one in which we take in excess salt, perhaps through eating salty things. Otherwise, loss of salt and fluid is a serious disadvantage in warm climates. Our tear ducts apparently had a similar function.

e) Other primates, hairy ones, attract mates partially through odors from their apocrine glands dispersed all over their skin. We have lost most of our apocrine glands, perhaps useless in water.

f) Our fat deposits consist of brown and white fat. The brown stuff, colored by blood supply, is easily metabolized for temperature regulation. Hairlessness might imply a greater need for brown fat. We actually have more white fat, diufficult to metabolize, and have it dispersed all over our bodies, just under our skins where it seems more valuable as insulation. Humans (the Ama divers and channel swimmers) can survive in frigid water for long periods after training.

g) Our larynx position, dropped lower in our throats is consistent with requirements for swimming and diving, for the rapid exchange of gases with the atmosphere. It is a disadvantage in dry settings.

h) We have voluntary control of our breathing to an unusual degree, a trait consistent with swimming and having another benefit of making speech possible.

i) Our face to face mating positions are more consistent with those of aquatic mammals as is our (blush) penis size. Aquatic mammals also have hymens and do not display signs of estrus.

j) Brain growth is sometimes attributed to rapid climatic changes associated with glaciation; Morgan sees it as also heavily influenced by available diet. Living in aquatic settings makes a rich supply of omega 3 and 4 fatty acids available. Neoteny is given some credit for our larger brains; the creatures carrying the least mature features into adulthood are porpoises and whales.

k) Finally, there is the "baboon marker." Baboons genetically carry and transmit a specific virus; 40 primates were tested for exposure to the baboon marker. Twenty-three were positive for the marker, all were of African origin. Seventeen were negative; none of them came from Africa. Humans do not carry the baboon marker.

Morgan's book is 148 pages of fun. She has several examples of key evolutionary findings (e.g. those of Raymond Dart, originally suggesting hominid evolution in south Africa) being ignored because of their inconsistency with prevailing beliefs (1, 2). She has a concise, humorous style; I'm grateful someone asked about the appendix (I still don't know what it did) and led me to buy her essays. I'm curious about the present status of her model; silence could mean everyone believes it (not likely), that no one wants to realign their former thoughts (plausible), or she's been blown out of the water and I didn't hear about it.

Another possibility for the phenomena described by Morgan is the "homebox" genetic sequence. The "homebox" is a finite group of genes that powerfully regulates the expression of all the others. The homebox is highly simiilar across widely varying species. Given that our genetic identity to chimps is estimated to be 96-99%, there is some speculation that changes in a few homebox genes could make us different in a lot of ways all at once, instead of our evolving each trait separately.

NOTES:

1) The Aquatic Ape Theory has not been spontaneously and widely accepted. The Adapted Mind (Barkow, Cosmides, & Tooby 1992) is woven with savanna assumptions and even some research summaries on those foundations. Thomas Kuhn (1992, The Structure of Scientific Revolutions (3rd Ed), 1992, Chicago: Univ. of Chicago Press) spoke eloquently about the many episodes of scientists ignoring evidence. "Let us assume that crises are a necessary precondition for the emergence of novel theories and ask next how scientists respond to their existence. Part of the answer, as obvious as it is important, can be discovered by noting first what scientists never do when confronted by even severe and prolonged anomalies. Though they may begin to lose faith and then to consider alternatives, they do not renounce the paradigm that has led them into crisis." (p.77).

2) Geographic isolation is thought to encourage genetic diversity. Rouhani and Jones (1992) have a startling set of remarks, based the presence and absence of gene sequences. Of 4 particular sequences, 3 are found in all non-african groups, the 4th is found only among Africans. They infer a bottleneck which lasted for about 50 years in which only 6 reproductively active individuals became ancestors of all non-African stocks. Another estimate of 500 persons for about 200 years could produce a similar shift in gene patterns. Were they all on Danakil Island?

Barkow, J., Cosmides, L., & Tooby, J. (1992) (Eds.) The Adapted Mind: Evolutionary Psychology and the Generation of Culture. NY: Oxford.

Morgan, E (1990) The Scars of Evolution: What Our Bodies Tell Us About Human Origins. NY: Oxford.

Rouhani S & Jones S (1992) Bottlenecks in human evolution. In Jones S, Martin R, & Pilbeam D (Eds) The Cambridge Encyclopedia of Human Evolution. NY: Cambridge Univ. Press, pp. 281-283.

Verhaegen M (1987) The Aquatic Ape Theory and some common diseases. Medical Hypotheses, 24, 293-300 (as cited by Morgan)

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