The Waterside Hypothesis defined

The Waterside Hypothesis... What is it?

The Waterside Hypothesis (aka AAH 'weak version'):

The hypothesis that moving through water has acted as an agency of selection in the evolution of humans more than it has in the evolution of our ape cousins. And that, as even relatively weak selection may result in profound and rapid phenotypic changes, many of the major physical differences between humans and the other apes are best explained as adaptations to moving (e.g. wading, swimming and/or diving) better through various aquatic media and from greater feeding on resources that might be procured from such habitats.

(This is an overarching definition which comprises of a series sub-hypotheses, defined here, which provided more detailed, falsifiable predictions. The overall hypothesis is a superset of these sub-hypotheses, therefore it too is testable. It is suggested that if hominids lived in water-side habitats then each sub-hypothesis not only stands on its own but draws synergic strength and parsimony when combined with the others.)

Discussion

Considering that most authorities on human evolution seem to be convinced that the AAH is fatally flawed it might come as some surprise that it is doubtful if any of them could even tell you what it is. This might sound a little far-fetched but, technically speaking, neither Alister Hardy nor Elaine Morgan ever did actually define what the 'aquatic ape hypothesis' was in an unambiguous way which is consistent with the fossil record as we understand it today.

All of their work seems to have been targeted at recruiting interested scientists to take the hypothesis seriously and to study it. Hardy's (1960) paper in New Scientists was little more than a request for comments and Elaine Morgan's five books, although gaining in seriousness each time, remained popular science pieces which aimed to stimulate the mind of the reader into thinking that something was amiss. Both advocates succeeded to a large extent but it is my view that it a serious criticism of their contribution that, even today, no-one can point to any piece of literature where the AAH is simply and unambiguously defined.

Of course this has led to each and every observer, whether they are sceptical or supportive, to arrive at their own personal interpretation of what the theory means to them. This has led to many problems, including the fact that, for many, the AAH is rather vague and nebulous. All of this raises a serious question: If we can't even say, with any authority, what it is - how can it be evaluated? It seems rather clear, from the literature about the aquatic ape hypothesis, that commentator's scepticism of the idea is directly proportional to one's interpretation of greater proposed aquaticism. The more aquatic on thinks the AAH is proposing our ancestors to be, the more sceptical about it the observer tends to get. There are only two papers in the literature (Lowenstein & Zihlman 1980 and Langdon 1997) which have attempted an outright critique of the hypothesis and it is clear that both seem to assume it is suggesting a very aquatic past. Both make comparisons with true aquatic mammals and when humans and their ancestors fall short somehow, they claim this shows that the AAH must be wrong. Clearly the only relevant comparison in this debate is between humans and chimpanzees, our nearest relatives. Which is the more aquatic of those two? Obviously, it's humans. The other major 'rebuttal' against the AAH is Roede et al (1991). It is true that the overall conclusion from the proceedings of the Valkenburg Symposium was against the AAH. The symposium included eleven proponents of the AAH and eleven opponents - kind of like some big football match decider. And the result was certainly no thrashing. More like a 1-0 win in the last minute of injury time after a dodgy refereeing decision. You might think this conclusion is just the view of a biased fan. ("We woz robbed!" claimed the AAHer.) But before concluding that you should be clear what kind of AAH they were dismissing. Vernon Reynolds in Roede et al (1991:340), as part of his concluding comments, wrote that although "overall, it will be clear that I do not think it would be correct to designate our early hominid ancestors as ‘aquatic’..." He continued, "...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." This, to me, seemed very odd, because he was basically arguing in favour of what I had always understood the AAH to be (merely that moving through water had influenced our evolution to some degree), whilst simultaneously rejecting what he obviously interpreted the AAH to be (that there was a full-on aquatic ape). Clearly the whole aquatic ape idea is rather a vague mess and there's an urgent need for some clarity here.

I must state, from the outset, that not all versions of the AAH are vague and nebulous. It should be noted that there are, in fact, several variants of some kind of AAH and each of them has their own proponents, their own strengths and weaknesses. For example, the hypothesis held by Marc Verhaegen et al actually is not vague at all. Marc's hypothesis is, if anything, the opposite. It is very precise about its claims, it's timescales, the lifestyles proposed for early Hominoidae as well as later Homo. In fact it's hard to think of an area of human evolution that is not covered by Marc's amazingly energy for coming up with plausible explanations. The trouble with Marc's ideas, in my humble opinion, is that they're too precise. If you don't see Neanderthals and/or Homo erectus as being heavy-boned bottom diving people you find yourself on the other side of another kind of divide. If you don't see apes as being particularly aquatic but see the strength of the AAH as it's explanatory power in distinguishing between man and ape, then again, you might find some of Marc's ideas strange.

The fact that there are several AAH variants makes defining it a little more challenging. In particular they tend to make different assumptions about the timescale involved and the habitat - marine or fresh water, for example. It struck me that what was needed was to determine a kind of 'lowest common denominator' of each of these variants and then fuse (I might prefer to use the term 'hybridise', perhaps) them into a simple, all-encompassing definition of the AAH. This, I have done. The definition below, I think, covers every AAH variant I know, without contradiction. It makes no assumptions about timescale, whether there was a distinct aquatic phase or not. And that made no assumption is made about whether all apes had been more aquatic in the past, or just Homo. You may notice that it is based upon the wording of Vernon Reynolds statement cited above.

The Waterside Hypothesis (aka AAH 'weak form'):

(This is an overarching summary of the overall hypothesis. Click the hyperlink for a more thorough definition outlining falsifiable predictions.)

Responses

I am very pleased (and proud) to report that when I wrote to Elaine Morgan about this in June 2004 asking for her comments and whether or not she was prepared to give it some kind of formal endorsement she replied... "I'll drink to that!" In her typical modest style, she wrote... "Delighted to endorse it. But neither the definition nor anything else you say requires my endorsement." (Morgan pers. cor. 1st July 2004)

Marc Verhaegen also gave the definition his support in October, writing, "Excellent definition, nowhere refuted by the facts. Perhaps add: "& feeding, at least in part, on aquatic foods"?" on the sci-anthropology-paleo newsgroup. I have tried to accommodate that suggestion. See this link for more of his thoughts on this subject.

The definition is only a starting point and I welcome any comments people might have to flesh it out a bit. I'm determined not to put too much detail on it because there will be AAH variants which will do that. I have my own AHAH (hybrid hominid) model, of course, which I promote elsewhere on this web site and I would not, for instance, want to imply that this broad definition included anything of my own, only that my own was compatible with this one.

If anyone would like to give any kind of feedback on this definition, please e-mail me.

Algis Kuliukas

September 2007

References:

Langdon, John H (1997). Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis. Journal of Human Evolution 33:479-494

Lowenstein, Jerold M; Zihlman, Adrienne L (1980). The Wading Ape - A Watered-Down Version of Human Evolution. Oceans 17:3-6

Reynolds, Vernon (1991). Cold and Watery? Hot and Dusty? Our Ancestral Environment and Our Ancestors Themselves: an Overview. In: Roede, Machteld; Wind, Jan; Patrick, John; Reynolds, Vernon (eds.), (1991). Aquatic Ape: Fact of Fiction: Proceedings from the Valkenburg Conference. Souvenir Press (London)