The Aquatic Ape Theory: Jury Still Out ?
Posted By Leslie Randall on 17 October 2005
The first book is The Red Ape: Orangutans and Human Origins by Jeffrey H. Schwartz (Westview Press, 2005) in which the author battles a veritable mountain of molecular evidence to insist that orangutans and humans share a direct common ancestor, thus pushing chimps out of the scientific limelight. But why should we care, aquatically speaking, if it’s orangutans who share a common history with us ?
The second book provides the "why", for if orangutans are our sister species, they share with us a fondness for water. Far from being afraid of it like chimps, wild adult orangutans have been observed wading across streams and willingly entering the water, walking upright, to splash and frolic. The Orangutans by Gisela Kaplan and Leslie J. Rogers (Perseus Books Group, 2000) points out that orangutans had to have crossed many large river systems to successfully colonize Borneo and Sumatra. The book also notes that the orangutan’s traditional and preferred habitat is always lowland with water easily accessible nearby. Only human encroachment has forced them onto higher, dryer ground. Similarly, in Orangutans: Wizards Of The Rain Forest by Anne E. Russon (Firefly Books Ltd,2004) there is a picture (p. 30) of a young adult orang mucking about in a pond, followed by a heartrending photo (p. 62) of abandoned infants at the Camp Leakey rehabilitation sanctuary in Borneo getting a ride to the river in a wheelbarrow for their bath and play time.
Combine these images of water-loving orangutans with the fact that they periodically walk bipedally when the mood suits them, and one can begin to picture the sort of Miocene era (12-8 MYA) primate Elaine Morgan had in mind for an aquatic interlude leading to. . .us, and, the similarities between orang and human listed in The Red Ape begin to look really significant.
First, the exciting stuff.
Unique among primates (except man), orangutans have abandoned an estrus cycle. Rather than coming into heat, with obvious ano-genital swelling to advertise the fact (which causes absolute mayhem in chimp colonies), female oranges have a regular menstrual cycle uncannily close to ours (28.4 vs 27.3 days). They engage in sexual activity throughout the month, and form consortships that last several weeks and may be repeated by the same pair year after year. Make no mistake - this “loss” of estrus represents a crucial biochemical and behavioural shift. In humans the “hiding” of estrus, and the move to continuous sexual receptivity, are seen as key requirements for evolving large cooperative social groups. With orangutans as our relational forebears, we don’t have to explain how hominids made the huge leap from a testosterone-charged male-dominated social system (chimps) to pair bonding. [Editor's Note: Certain university campuses may yet prove exceptions to the explanatory power of the orantugan-ancestry model.]
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