Why the Aquatic Ape Hypothesis doesn’t hold water

Among this week’s new videos from TED, was a talk given by Elaine Morgan – the chief promoter of the Aquatic Ape Hypothesis (AAH). The AAH was first formulated by Alister Hardy and is the idea that human evolution went through an aquatic stage, which in turn explains many of the features of the human physiology. For anybody with a poor understanding of evolutionary biology the AAH arguments can seem quite compelling. Instead of repeating the numerous reasons why the AAH fails (Jim Moore has an entire website dedicated to this), I wish to address some of the specific arguments made in this video.

Morgan starts off my stating that “… there’s one aspect of this story which they [evolutionists] have thrown no light on and they seem anxious to skirt around and step over it and talk about something else. So I’m going to talk about it. It’s the question of why are we so different from the chimpanzees?”. Either Morgan has not been reading the hundreds of research papers that have addressed these important questions or she is trying to hoodwink her audience. Palaeoanthropologists and primatologists have long recognised the value of studying human and chimp differences in order to understand our shared evolutionary history. In fact, it is impossible to talk about functional anatomy and phylogenetic history in humans without reference to our closest extinct and living hominin relatives.

She continues: “Yet when you look at the phenotypes. There’s a chimp, there’s a man. They’re astoundingly different. No resemblance at all.” I am hearing this correctly? No resemblance at all? Even a five year old can see the striking similarities between chimpanzees and humans. To suggest that there is “no resemblance at all” is laughable. It was the similarities of humans to other non-human primates that led Charles Darwin to argue for common ancestry between humans and the great apes. Even without the fossil record and the unambiguous molecular evidence, the morphological similarities alone would be enough to suggest a shared common ancestry of chimps and humans.

Throughout the talk she constantly refers to humans as naked, as if to suggest we are hairless. One need only look at a shirtless Alec Baldwin, Robin Williams or Andy Garcia to know this is not the case. While it is true that humans are less hairy than the rest of our primate kin there are far more compelling hypotheses to explain our lack of hair (thermoregulation, defence against parasites or sexual selection). She claims that hairlessness is an aquatic trait when in fact most aquatic/semi-acquatic mammals are in fact hairy. Otters, polar bears, seals, and walruses are but some examples that spring to mind.

Regarding the failed savannah hypothesis of bipedalism Morgan has this to say: “What do scientists do when a paradigm fails… carry on as though nothing had ever happened… If they haven’t got a paradigm they can’t ask the questions… The only other option open to them is to stop asking the questions. So that is what they have done now. That is why you don’t hear them talking about it.”

When paradigms fail science marches on. When was the last time you heard a scientist defending the merits of Lamarckism, psychoanalysis and phrenology? Morgan is correct that the savannah hypothesis doesn’t weigh up against the evidence but she mistakenly claims that the anthropologists haven’t let go of this idea. The savannah hypothesis was formulated in a time when there was a dearth of palaeoecological data for the most important African archaeological sites. As more data came in, anthropologists changed their models correspondingly. No serious anthropologist still adheres to the savannah hypothesis. Morgan chooses to ignore this fact, instead preferring the easier route of attacking a strawman. In the references section below, you will find just a spattering of the work anthropologists have been doing on palaeoecological reconstructions of the environments occupied by our forebearers. These papers address the very questions Morgan asserts that scientists have stopped asking. Does she not read the anthropological literature or does she just choose to ignore it? She implies that because the savannah hypothesis is false it somehow offers support to the AAH. In fact, the consensus opinion suggests that neither savannah nor aquatic environments were very important in the early stages of human evolution, but rather our hominin ancestors exploited wood and forest habitats. A number of anthropologists have proposed an arboreal origin of hominin bipedality (Crompton 2008; Pickerford 2006; Senut 2003, 2006). In fact, the best known human ancestor Lucy shows clear arboreal adaptations.

Morgans proceeds by stating that “there is only one circumstance in which they always, all of them [non human primates], walk on two legs and that is when they are wading through water.” Contrary to Morgan’s claim, the data have shown apes to be bipedal more often on land than in the water.

She follows this up by saying that the fat in humans is similar to that seen in aquatic mammals. Humans have a similar number of fat cells compared with other primates. The increased subcutaneous fat seen in humans is most likely a result of diet rather than an evolutionary adaptation. Non-human primate obesity is well documented, particularly in primates kept in captivity (Videan 2007; Altmann et al 1993; Kemnitz et al 1989; Schwartz et al 1993). Moreover, the distribution of fat in humans runs contrary to need aquatic mammals have for streamlining.

Ten minutes into the talk she states that “the only creatures that have got conscious control of their breath are the diving animals and the birds”. Humans are not the only non-aquatic mammal which can hold its breath. Various monkeys, for instance, can and do hold their breath, as well as dogs.

Finally, she asserts that “we are streamlined.” Humans are anything but streamlined. Our motion in the water is generally quite wasteful. Ask any swimming coach. Fish have a fusiform shape (tapered at both ends), which is ideal for moving through the water with the least amount of resistance. Let’s put this into perspective. The sailfish records speeds of up to 116 km/hr (72 mph), while Michael Phelps can average a measly about 6.5 km/hr (4 mph) on a good day! Our body shape is a consequence of our adaptation to bipedalism, the requirements of childbirth in women, sexual dimorphism and sexual selection.

While I generally enjoy listening to the speakers at TED, I think this is an idea NOT worth spreading.

References

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Altmann J, Schoeller D, Altmann SA, Muruthi P, Sapolsky RM (1993) Body size and fatness of free-living baboons reflect food availability and activity levels. Am J Primatol 30: 149–61.

Andrews P (1996) Palaeoecology and hominoid palaeoenviron-ments. Biol Rev 71, 257–300.

Andrews P, Humphrey L (1999) African Miocene environments and the transition to early hominines. In African Biogeography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 282–300. New York: Oxford University Press.

Andrews P (2007) The biogeography of hominid evolution. J Biogeogr 34, 381–382.

Andrews P, Kelley J (2007) Middle Miocene dispersals of apes. Folia Primatol 78, 328–343.

Andrews P, Bamford M (2008) Past and present vegetation ecology of Laetoli, Tanzania. J Hum Evol 54, 78–98.

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Kovarovic KM, Andrews P, Aiello L (2002). The palaeoecology of the Upper Ndolanya Beds, Laetoli, Tanzania. J Hum Evol 43, 395–418.

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Schwartz SM, Kemnitz JW, Howard CF Jr (1993) Obesity in free-ranging rhesus macaques. Int J Obes 17:1–9.

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