Revisiting Water and Hominin Evolution
Phillip V Tobias 2011
Was Man More Aquatic in the Past? p.3-15

For many investigators, the rôle of water in the evolution of the Hominini refers to the development of a nr of anatomical & physiological features, which hominins are thought to share with water-adapted animals.
However, in the last dozen years, there has been emphasis on other ways in which water, and the proximity to water, have been probable influences in hominin evolution.
This chapter reviews each of 5 ways in which water has influenced or might have affected human evolution. This pentapartite analysis singles out water for drinking, for keeping cool, for global dispersal, as a basis for aquatic adaptations & for the
ingesting of aquatic foods.
In contrast with the heavy, earth-bound view of hominin evolution, which has predominated hitherto, an appeal is made here for students of hominin evolution to buoy up, lighten & leaven their strategy by adopting a far greater emphasis upon the rôle of
water & waterways in hominin phylogeny, diversification & dispersal from one water-girt milieu to others.
Some evidence is adduced to show the value & potential of this course of action.

LANGDON’S ANALYSIS AND MY FINAL (?) THOUGHTS
Until recently there had been virtually no serious discussion of the AAH, but John Langdon (Univ.Indianapolis) made a critical analysis in 1997 [61], one of the first by someone who is not an avowed supporter of the AAH (see Ch.15).
His 1997 study examined each of a long list (32) of features that had been proposed as aquatic traits.
Of these, he concluded that 3 were “possible aquatic adaptations”, but none of these 3 is available from the fossil record.
Of the 32 characters, 7 were found to be “consistent with AAH”, and 4 of these 7 may be read from the fossil record.
In all, therefore, only 4 of the 32 features may be read or inferred from the fossil record.
I have analysed Langdon’s critique, as well as the evidence put together by the authors mentioned above and collated & synthesized by Elaine Morgan in her books, esp. "The aquatic ape hypothesis" [39] & "The scars of
evolution" [49].
Evidence has been presented, and is now widely accepted, that the powerfully competing savannah hypothesis for the origins of hominin bipedalism is no longer tenable [62].
In the face of this, I believe that palaeo-anthropologists have a duty to re-examine the claims for the AAH [14,15,34].
The following sums up the position at present, as I understand it, and it represents my current standpoint:
(i) The AAH highlights a real problem that needs to be addressed. It requires more research, not only on the features of humans, their ancestors & their closest living ape relatives, but also on those of unequivocally aquatic mammals, to determine what
features are common, if not universal, among water-adapted animals.
(ii) I am not yet convinced that the AAH is correctly applied to all of the 32 morphological & functional traits that its proponents have proposed as ‘aquatic traits’ of the hominins, but for at least some of the enumerated characters, the hypothesis
may well provide the most reasonable, or perhaps the only, explanation that has yet been proposed.
(iii) To test the hypothesis, studies should address not only the soft tissue features (their anatomy, histology, biochemistry & physiology) but also the skeleton. Only if there are water adaptations of the bones themselves, will the hypothesis be
testable by the examination of relevant fossil bones.
(iv) We should be wary of telescoping too many phases & characteristics of hominin evolution under this single, over-arching hypothesis, incl. traits some of which made their appearance very early, and some very late in phylogeny.
(v) As a research strategy, those traits should be expunged from the AAH list, for which there are alternative explanations or canonical hypotheses, if these alternative hypotheses are better supported and on testing have not been refuted.
(vi) Of the 32 items on the list compiled by Langdon [60], after the removal of those traits for which there are sounder explanations, what is left may still be found to be substantial enough to warrant more research being devoted to the remaining traits
in relation to the AAH and more serious consideration being given to the AAH (see Ch.15).
(vii) Above all, let us try to keep our thought processes open to changes of paradigms, and esp. to the change, which would be necessitated if the AAH proves to be valid for some phenotypic features of modern & earlier hominins.
CONCLUSIONS
Each of the 5 ways in which water influences or might have affected human evolution (drinking, keeping cool, anthropo-geographical dispersal, aquatic adaptations, aquatic foods) requires further examination & careful
researching.
In sum, the rôle of water, while long appreciated & emphasized by ecologists, has been sadly neglected by human evolutionists.
This article is a plea for the heavy, earth-bound view of hominin evolution to be buoyed up, lightened & leavened by a far greater emphasis upon the rôle of water & waterways in hominin development, diversification & dispersal.

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