Bipedal – The Aquatic Ape Theory

Posted by arjaybe on August 31, 2012
Posted in: Uncategorized. Tagged: , . 14 comments


See also parts one and three.

Last time, we looked at the Savanna Theory as an attempt to explain the transition that early human ancestors made from being forest dwellers to living on open ground. It does a pretty good job of it, but there are some rough patches. For instance, it spends a lot of time explaining how living out on the open grassland contributed to our bipedal gait, while new evidence shows we were upright walkers before we left the trees. Another problem is that it can’t account very well for our unique lack of hair, especially compared to other primates.

There is another theory that focuses on that period from the divergence of our line to the appearance of definite hominids in the fossil record. The Aquatic Ape Theory posits that our forebears spent a prolonged era in a wet, semi-aquatic environment, and that contributed to the evolution of a body plan that was very different from their relatives who stuck to the drier parts of the forest.

There are several things about us that are decidedly different from other mammals, most notably from other primates. Immediately obvious is our nakedness, or relative lack of hair. Not so obvious is our fatness, which is about ten times what it should be. Much of the fat is attached to the skin, while other land mammals tend to store their fat internally. Our bipedalism was retained and refined, even though other primates evolved quadrupedal gaits on the ground. We breathe differently from other land mammals. Unlike most other mammals, we have conscious control of our breathing. The other mammals with such control include seals and dolphins.

Here are some other differences. Humans sweat differently, from different glands in our skin, than do other mammals. Such excessive loss of water and salt doesn’t imply a dry environment, such as the savanna. We shed salty water from our eyes and noses, in addition to normal cleansing tears. We have millions of relatively large sebaceous glands that exude oil all over our heads and torsos. This is usually done to waterproof an animal’s fur or skin. Our brains have managed to grow unusually large. Other primates have larger brains than are found in most animals of their size, but they don’t approach the phenomenal growth rate of our brain.

These are some of the things the Aquatic Ape Theory has to explain. Let’s see how it does.

In 1930, while he was reading “Man’s Place among the Mammals,” by Frederic Wood Jones, Sir Alistair Hardy noticed a similarity between humans and aquatic mammals. They and we have a layer of fat attached to the skin which, in marine mammals, is called blubber. This led to the conjecture that there might have been a more aquatic phase in our evolution after our line and that of chimpanzees split from a common ancestor. Because this was outside his field, marine biology, and because he was shy of controversy so early in his career, Hardy didn’t make his ideas public for thirty years. When he did they were received first with controversy before being generally ignored.

The hypothesis got mentioned in Desmond Morris’ 1967 book, “The Naked Ape,” where it was seen by Elaine Morgan, who has been its most tireless advocate.
Elaine Morgan It still gets very little serious attention from paleoanthropologists and all of its claims have been criticized and found inadequate by its detractors. The aquatic theory still claims to be the only one that integrates and explains the many enigmas surrounding our differences from our primate relatives. We’ll look at some of them: our relative hairlessness, our fatness, bipedality, breathing, sweating and our large brains.

Of hundreds of primate species, only humans are hairless. Mammals become hairless in only two habitats: underground or around water. All the other mostly furless mammals that live above ground are either swimmers or wallowers, such as dolphins, manatees, hippos and tapirs. Even rhinos and elephants, which are drylanders now, had a more aquatic past and will wallow given the chance.

Humans are the fattest primates, having ten times the fat expected in an animal our size. Our fat is of the aquatic type rather than the hibernating type.

We are the only mammals that are primarily bipedal. Although there is evidence that brachiating apes developed bipedalism in the trees, the Aquatic Ape Theory says it was required for wading in the semi-aquatic habitat under the trees. Given the problems it still gives us millions of years later, such as back pain, hemorrhoids and hernias, bipedalism must have been necessary for some reason.

We are the only land mammals to have voluntary control of our breathing. Otherwise it is only found in aquatic mammals such as dolphins.

We sweat differently from other mammals, using different glands in the skin. We shed copious amounts of water and salt, okay in a semi-aquatic environment, wasteful on the dry savanna.

Finally, our brains are much bigger than chimps’. Why us and not them? Brain growth is better with abundant omega-3 fatty acids, which are concentrated in fish, shellfish and the eggs of seabirds. Without access to these fatty acids we might have been just another large ape.

What do you think? Does the Aquatic Ape Theory explain as much as the Savanna Theory?

rjb

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14 comments on “Bipedal – The Aquatic Ape Theory”

  3. Humans didn’t descend from aquatic apes, of course, although our ancestors were too slow & heavy to run over open plains as some anthropologists still believe.
    Instead, Pleistocene Homo populations simply followed the coasts & rivers in Africa & Eurasia (800,000 years ago, they even reached Flores more than 18 km overseas), google “econiche Homo”.
    –eBook “Was Man more aquatic in the past?” introd.Phillip Tobias
    http://ebooks.benthamscience.com/book/9781608052448/
    –guest post at Greg Laden’s blog
    http://scienceblogs.com/gregladen/2013/01/30/common-misconceptions-and-unproven-assumptions-about-the-aquatic-ape-theory

    Reply

    • Thank you for your comment. I immediately went over to Scienceblogs and read your post. Very impressive and informative.

      Did you read the companion to this article: Bipedal – The Savanna Theory?

      Even though we “didn’t descend from aquatic apes,” would your analysis agree at all with the later description of “semi-aquatic?” From my naive point of view, that seems similar to what you say in your post.

      Again, thank you for taking the time to comment.

      rjb

      Reply

      • Thanks a lot, but sorry for this late reply. Yes, “semi-aquatic” is a good term, but biologically more correct IMO is “littoral”, e.g. H.erectus & relatives did not run to Crete, Cyprus, Flores, Sulawasi etc… My last paper: The aquatic ape evolves: common misconceptions and unproven assumptions about the so-called Aquatic Ape Hypothesis. Hum.Evol.28:237-266, 2013.

        Reply

  4. Sorry for this belated answer, rjb. Thanks, yes, “semi-aquatic” is correct IMO.
    I think we can schematically see ape & human evolution as follows IMO:
    – aquarboreal theory of Mio-Pliocene hominoids: early”apes” incl.Oreopith., Sahelanthropus, Orrorin, australopiths etc. were vertical (orthograde, ie, with vertical lumbar spine) aquarborealists (ie, living in swamp forests & later wetlands, spending a lot of time wading or floating in the water, feeding on surface plants & animals (aquatic herbaceous vegetation, eg, papyrus sedges, & hard-shelled invertebrates, eg, snails or mangrove oysters), climbing vertically in the branches above the swamp, not unlike lowland gorillas in forest bais.
    – lit(t)oral theory of Pleistocene archaic Homo, trekking along coasts & later also rivers, parttime diving for sessile animals (shellfish) & probably plants (seaweeds).
    – wading hypothesis of late-Pleistocene H.sapiens, wading with complex tools (harpoons etc.) in very shallow (often fresh)water, collecting more mobile animals (eg, fish, waterfowl, ungulates in mud etc.) & shallow aquatic & waterside plants (eg, rice).
    Human Evolution will soon devote 2 special editions to the semi-aquatic theory:

    Proceedings of the Symposium held in London on 8-10th May 2013
    “Human Evolution: Past, Present & Future”
    Human Evolution:

    SPECIAL EDITION PART 1 (end 2013)

    Introduction – Peter Rhys-Evans

    1. Human’s Association with Water Bodies: the ‘Exaggerated Diving Reflex’ and its Relationship with the Evolutionary Allometry of Human Pelvic and Brain Sizes – Stephen Oppenheimer

    2. Human Ecological Breadth: Why Neither Savanna nor Aquatic Hypotheses can Hold Water – JH Langdon

    3. Endurance Running versus Underwater Foraging: an Anatomical and Palaeoecological Perspective – Stephen Munro

    4. Wading Hypotheses of the Origin of Human Bipedalism – Algis Kuliukas

    5. The Aquatic Ape Evolves: Common Misconceptions and Unproven Assumptions about the So-Called Aquatic Ape Hypothesis – Marc Verhaegen

    6. The Epigenetic Emergence of Culture at the Coastline: Interaction of Genes, Nutrition, Environment and Demography – CL Broadhurst & Michael Crawford

    SPECIAL EDITION PART 2 (begin 2014) with 12 contributions

    Reply

  6. Thanks a lot, rjb, sorry for this very late reply. A short summary & update of the “littoral theory” (more correct IMO than “aquatic ape”):
    Human ancestors did not become bipedal by moving from the forests to the plains (schematically: ape=>human = forest=>plain = 4-legged=>bipedal): primates that move from forest to savannah become more, not less quadrupedal (“baboon paradox”); sweating requires salt & water (=scarce in arid grasslands); etc. Comparative, paleo-environmental & other data show:
    (1) Plio-Pleistocene australopithecines (=fossil African apes?) were typically wetland species (K.Reed 1997). This helps explain the remarkable combination of bipedality (e.g. for wading) & curved hand-bones (vertical climbing). Human fetuses never have hand-like feet, but prenatal African apes have more humanlike feet (with longer & adducted big toes) which later become more hand-like (C.Coon 1954). This suggests Pan & Gorilla had more bipedal ancestors (e.g. for parttime wading for papyrus, frogbit, waterlilies etc.), google e.g. bonobo wading, or gorilla bai.
    (2) Our Pleistocene ancestors (archaic Homo) did not disperse intercontinentally walking or running over the open grasslands, but followed African & Eurasian coasts & rivers (“coastal dispersal”l, S.Munro 2010), walking & wading bipedally & parttime diving for waterside, littoral & shallow-aquatic foods (= richest in brain-specific nutrients: DHA etc., S.Cunnane 2005), even colonizing islands overseas: Flores, Crete, Cyprus etc.
    Homo’s diet included animal (e.g. shellfish opened with hard tools, waterside carcasses of herbivores & marine mammals, salmon & other fish) as well as plant foods (e.g. traces of waterlily roots in neanderthal dental calculus & of cattails on their tools).
    Homo’s brain enlargement (e.g. DHA) & parttime shallow diving (which requires breathing control) were preadaptive to human spoken language.

    Reply

  8. There is a new version of the aquatic ape hypothesis, that finally makes sense: humans evolved in western Africa, where there are no fossils, from isolated chimpanzees on a Galapagos-like volcanic island called Bioko. They rafted there, found no forest foods, and therefore ate seafoods, and evolved all the human features. See this new version: http://AquaticApe.net

    Reply

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