On our occasional trips to the New Jersey shore, my wife is always the first one in the water. While I’m cautiously wading in, dreading that final slap of cold water just below my waist, she’s already frolicking in the waves, egging me on to just jump in and get it over with. Eventually I too become submerged (either willfully or by force of a wave I never saw coming), salt water inevitably shooting up my nose. Don’t get me wrong, I do enjoy warm days at the beach, but on each visit it seems that I as an individual, if not a representative of a population or species, am not well-adapted to a near-shore marine existence. Followers of the Aquatic Ape Hypothesis* (AAH), however, beg to differ.
[* I say "hypothesis" and not "theory" (AAT) because the writings of Elaine Morgan and others do not have enough supporting evidence to garner it the more prestigious title of "theory." Given the current paucity of evidence and research, the Aquatic Ape Hypothesis is precisely that and no more.]
Before discussing the current manifestation of the AAH, we need to go back to a time when the truth of evolution had yet to fully take hold in the minds of scientists and philosophers. The Ionian philosopher Anaximander (610-546 BCE), student of Thales, suggested that the world first existed in an entirely aquatic state, the recession of the globe-consuming waters creating life. In From the Greeks to Darwin (1905), famed American Museum of Natural History president Henry Fairfield Osborn described the views of Anaximander as follows (a similar treatment is given in Osborn’s Man Rises to Parnassus, as well);
He conceived of the earth as first existing in a fluid state. From its gradual drying up all living creatures were produced, beginning with men. These aquatic men first appeared in the form of fishes in the water, and they emerged from this element only after they had progressed so far as to be able to further develop and sustain themselves upon land. This is rather analogous to the bursting of a chrysalis, then to progressive development from a simpler to a more advanced structure by a change of organs, yet a germ of the Evolution idea is found here.
We find that Anaximander advanced some reasons for this view. He pointed to man’s long helplessness after birth as one of the proofs that he cannot be in his original condition. His hypothetical ancestors of man were supposed to be first encased in horny capsules, floating and feeding in water; as soon as these ‘fish-men’ were in a condition to emerge, they came on land, the capsule burst, and they took their human form.
Like the works of many Ionian philosophers, the ideas and opinions of Anaximander do not seem to have taken hold (Aristotle ultimately becoming the preferred scientific and philosophical source for further consideration in Europe in centuries to come), and not much of his work remains. It is curious to note, though, that wrong as Anaximander was about the origins of humans, the reasons he uses to support his ideas (as relayed by Osborn) are very similar in approach to those of Elaine Morgan and some modern-day AAH adherents, as we shall soon see.
To the best of my current understanding, the hypothesis that man was a product of the sea did surface again until 1942 when Max Westenhofer of the University of Berlin published the book The Unique Road to Man. According to Donna Kossy’s book Strange Creations, Westenhofer’s treatment of an aquatic origin of mankind consisted of little more than mention of it as a promising hypothesis, however, and the outbreak of war prevented the professor from pursuing the line of inquiry further. The hypothesis would have to wait until March 5, 1960, when marine biologist Sir Alister Hardy presented a lecture on “Aquatic Man: Past, Present, and Future” to the British Sub-Aqua Club. The address caused quite a stir and led Hardy, who had been inspired by the layers of sub-cutaneous present in humans and some marine mammals he had seen skinned on a journey to the Antarctic in 1927, to write a series of articles in the magazine New Scientist to clarify his position on the subject. Kossy relates the words of Hardy from an April issue of the magazine (although the year is not specified);
My thesis is that a branch of this primitive ape-stock was forced by competition from life in the trees to feed on the seashores and to hunt for food, shell fish, sea-urchins, etc., in the shallow waters of the coast. I suppose that they were forced into the water just as we have seen happen in so many other groups of terrestrial animals. I am imagining this happening in the warmer parts of the world, in the tropical seas where Man could stand being in the water for relatively long periods, that is, several hours at a stretch. I imagine him wading, at first perhaps still crouching, almost on all fours, groping about in the water, digging for shellfish, but becoming gradually more adept at swimming. Then, in time, I see him becoming more and more of an aquatic animal going further out from the shore; I see him diving for shell fish, prising out worms, burrowing crabs and bivalves from the sands at the bottom of shallow seas, and breaking open sea-urchins, and then, with increasing skill, capturing fish with his hands.
Thus the more familiar image of the amorphous “Aquatic Ape” was born, wading out into the surf and feeling in the shallow sands for food. The early stage of such a transformation is awfully raccoon-like, as raccoons have incredibly sensitive hands that they use to feel about in streams and shallow waters for mussels, crayfish, and other morsels without being driven to become fully aquatic themselves. Nevertheless, the idea that man had his origins in a shallow sea rather than on a hot and brutal savanna was certainly controversial. Ever since Raymond Dart described the skull of the Taung Child in 1925 (shifting attention away from Europe and Asia for the origins of man) and the fossil assemblages of the South African caves were discovered, humans were thought to have evolved through a hunting culture, nearly every specialization that separates us from living primate relatives being due to our meat-craving societies. Indeed, the remains of Australopithecus found in South African caves (especially the jaw of a 12-year old child whose jaw appeared to have been fractured by a direct and accurate blow) like those Makapansgat suggested to Dart that these “proto-men” were not only skilled hunters, but also murderers and cannibals. Even though our understanding of these assemblages has greatly changed since Dart’s time (see C.K. Brain’s The Hunters or the Hunted?), the overall image of human evolution being intricately linked to meat-eating and hunting has dominated the discussion of our origins. Even more specifically, the considerations of our ancestors have nearly always focused on the male of the species, and even Hardy’s early ideas of an aquatic ape focused primarily on males.
In 1964, zoologist Desmond Morris published the bestseller The Naked Ape. Today the book is nearly useless outside of understanding the history of thought about human evolution, but when it was first published a short discussion of the AAH caught the attention of a woman named Elaine Morgan. On page 37 of the 1967 paperback edition, Morris states;
Another, more ingenious theory is that, before he became a hunting ape, the original ground ape that had left the forests went through a long phase as an aquatic ape. He is envisaged as moving to the tropical sea-shores in search of food. There he will have found shellfish and other sea-shore creatures in comparative abundance, a food supply much richer and more attractive than that on the open plains. At first he will have groped around in the rock pools and the shallow water, but gradually he will have started to swim out to greater depths and dive for food. During this process, it is argued, he will have lost his hair like other mammals that have returned to the sea. Only his head, protruding from the surface of the water, would retain the hairy coat to protect him from the direct glare of the sun. Then, later on, when his tools (originally developed for cracking open shells) became sufficiently advanced, he will have spread away from the cradle of the sea-shore and out into the open land spaces as an emerging hunter.
Unfortunately, [searching for fossils in marine or fluvial deposits or further research into the AAH] has yet to be done and, despite its most appealing indirect evidence, the aquatic theory lacks solid support. It neatly accounts for a number of special features, but it demands in exchange the acceptance of a hypothetical major evolutionary phase for which there is no direct evidence. (Even if eventually it does turn out to be true, it will not clash seriously with the general picture of the hunting ape’s evolution out of a ground ape. It will simply mean that the ground ape went through a rather salutary christening ceremony.)
Elaine Morgan read the brief treatment and qualifications (some of which has been omitted here for the sake of brevity) and wanted to know more about the possibility of our ancestors going through an aquatic stage of evolution. No information seemed to be available, and so Morgan wrote to Hardy in 1970, and he encouraged Morgan to push ahead with her research and desire to write a book about the AAH. The result was the bestselling The Descent of Woman, published in 1972. My copy is a little bit newer than that, being the Bantam 1973 edition, and featuring what appears to be a nude mother and child on the cover. Closer inspection reveals that something isn’t quite right, however; the mother I previously assumed was a representative of Homo sapiens looks like she’s been hit in the face with a frying pan. I didn’t know it at the time, but the text would reveal that the plump, nude, and long haired female on the cover was not drawn from life, but rather was Morgan’s idea of the Australopithecus specimen “Lucy” as Aphrodite.
Morgan’s first book is certainly a unique one, weaving in between “Just-so story” type paleo-fiction and long arguments about the female orgasm, including it’s fallacious mythical status. Indeed, the AAH only seems to occupy the first 1/3 of the book, only cropping up here and there in the following chapters, and receiving only a brief mention in the conclusion. Still, the way Morgan structures her argument in her first book will tell us much about her later works and the rise of the AAH as a popular idea. Early on in the work, we are introduced to a hypothetical female ape, not unlike Proconsul, living in Africa sometime during the Pliocene (~5.3-1.8 million years ago). During this time a hard life trying to find food and avoid predators was becoming even harder, Morgan hypothesizing that a terrible heat wave would change the way of life for many populations of these unnamed apes (from what I understand, however, the climate of the Pliocene began to approach our own and became cooler, drier, and had more seasonal distinctions rather than being a global hot-house).
Morgan’s ape was in a bit of a jam, that’s for sure. The water holes are said to be stalked by hungry cats and food was becoming scarce, and the imaginary female was not as fearsome or powerful as the males in her group. Eventually she was chased into the water by a large cat, and decides that, despite her distaste for water, “the seaside not at all a bad place to be. She found to her delight that almost everything on the beach and in the water was either smaller or more timid than she was herself.” Indeed, Morgan’s ape appeared to have found paradise. While other animals cooked during the “dog days of the Pliocene”, her ape (and by extension the population of apes) found what seems to be a sheltered and peaceful lagoon devoid of predators, scavengers, or other threats from either land or sea. “Leopards don’t come so far into the sea, nor sharks so near to the land,” we are told, and while leopards may not be attracted to water, sharks are well-known for their shallow water hunting habits. Crocodiles are not even considered, nor are stingrays, poisonous urchins, jellyfish, disease, infection, or any of the other biological problems that may come with an aquatic existence or change in ecological setting. The new home of the apes sounds better than Club Med, a watery Eden lacking in devious serpents and forbidden fruit.
As suggested by Morris and Hardy, the population of apes gets by on a diet of shellfish and relatively stupid sirenians that happen to come by, males making short work of the water-going creatures with rocks found along the shore. Given the amount of time that the apes would be spending in the water (they couldn’t have just subsisted by wading in or eating what washed up, or at least this is what is implied), bodies started to change. Males are paid little attention by Morgan, and the warm relationship between mother and child takes center stage. While most of the hair on the body would be lost as an adaptation to water (an odd conclusion given that otters, seals, and sea lions all are covered in hair), the hair on the head would be allowed to grow long, the water babies being able to curl their fingers into it and stay close to mom for a nap when they got tired of exploring off on their own. Conversely, breast feeding would still have to take place on shore, but the upright posture of the females (acquired from so much time in the water) would require the baby to be held at an awkward position in which they could not reach their mother’s nipples. This was solved by developing larger “hemispherical” breasts to reach down to the infant, even though larger breasts may cause infants problems when they try to get their mouths on them to breast feed (if the breast is so large that the infant’s nose is covered by it, breathing and feeding becomes difficult).
In searching for an aquatic example of such a striking characteristic, Morgan turns to the Florida manatee and other sirenians, many who have seen females with young noting the presence of “breasts” on the aquatic mammals. Interestingly enough, however, the manatee shares it’s ancestry with living elephants, the females of which also exhibit some rather sizable swellings when lactating. Robert Sapolsky, in his book A Primate’s Memoir, describes seeing such an unexpected shape on the chest of a female elephant for the first time;
Did you know that female elephants have breasts? I do not mean rows of teats, a mama elephant lying on her side with dozens of little piglet elephants nursing with their eyes still closed. I mean breasts, two huge voluptuous billowy mounds, complete with cleavage. I bet you had no idea, did you? Nor did I – it is a subject rarely broached in our public schools. I’m out in the bush that first month, armed with binoculars and stopwatch and notepad, spending the days carefully watching baboons mating left and right. And then, suddenly, some pachyderms come cruising past, and I see some elephant with these, well, breasts. And the natural first reaction is to think, Oh, great, I’m such a horny lascivious pathetic adolescent that after a mere month of isolation in the bush I’ve already cracked, I’m hallucinating breasts the size of Volkswagens on the elephants. Horrors, to have one’s psychotic break occur so soon, and to have it take the form of a puerile sexual obsession many embarrassing steps below gawking at National Geographic nudies. I was greatly relieved to eventually discover that the elephant’s breasts were real, that I was not having some Marlin Perkins wet dream.
It should be noted, however, that Morgan attributes an aquatic origin to elephants as well, primarily based upon their ability to shed tears (and therefore salt), as well as the ability of living Indian elephants to swim long distances in the ocean. Such considerations are a side trip from the main thrust of her argument, and no detail is given as to when, where, why, or how elephants arose from a water-dwelling species, only that a few characteristics in living animals point to an Aquatic Pachyderm Hypothesis.
Going back to the AHH, given about 10 million years in the water Morgan’s ape is substantially different than the one that was first driven into the waves by a predator. Referring to her as “Mrs. Australopithecus,” Morgan paints the following portrait (the artistic manifestation of which is found on the cover of the book);
So our hominid has a nose. I have no doubt that she also had fleshy nostrils, but considerable doubt that they evolved to make sex sexier for her mate. I think she was by no means the simian, cadaverous, lipless creature that artists sometimes reconstruct by covering her dug-up skull with a tightly fitting layer of hairy skin. The layer of fat which was rounding out her arms and legs and adding bulk to her breasts was also filling out her cheeks, and her nostrils, and her earlobes, and everting her lips… We would not have accounted her beautiful, with her low forehead and prognathous jaw, but the chances are that she was a chubby little creature with several superficial features resembling our own more nearly than they resembled any ape’s. And as for the expressions that flitted across that prehistoric countenance, her millions of years in the water had certainly left their mark on those also.
This is quite a different picture of “Lucy” than is often seen, but is there anything to it? Part of the advantage of the AAH is that Morgan doesn’t specify her ideas down to a scientific level, allowing her to poetically play with her ideas in any way she wishes, the female becoming more beautiful while the men continue to try and kill dugongs with rocks. This type of feminist reaction to the “Man the Hunter” narrative is the main connective feature throughout the book, and Morgan’s writing is far more concerned with the more graceful and beautiful evolution of woman, with sex ultimately bringing “sin” into the Garden.
In Morgan’s story, the genitals of the ancestral females went from facing backwards (making rear-mounting positions by the male easy) to facing downwards, a position that Morgan insists will not work for males, face-to-face mating being adopted as a must. Morgan’s reasoning for the change is that aquatic animals often undergo this type of genital shift (cetaceans are her primary example), but she generally ignores why the genitals should be shifted in the first place. In terms of cetaceans, the ancestors likely had their anal-genital openings in the position typical for quadrapeds; facing backwards at the location of the pelvis just under the tail, usually being at the most distal end of the body. As they evolved, the archaeocetes lost their hind limbs and their spines elongated, being the main source of propulsion, so rather than keep moving backwards with the spine the genitals stayed in the pelvic region “settled” on the ventral side of the body; where else they would have gone, I do not know. Given this morphological necessity, face-to-face mating became the only way cetaceans could copulate. Seals and sea lions, on the other hand, still have their anal-genital openings near the distal most parts of their bodies because that is where the pelvis is and there was no need to change mating styles, and males still mount females from behind. Even beyond such considerations, I do not see how the rear-mount strategy can be dogmatically ruled out, and I have a feeling that because such a position is considered “kinky” by some it was essentially ruled not to have happened. In fact, the retention of rear-mounting with the shift in female genitals could help explain elongation of the penis in males (they’d have to extend a bit farther), although this matter is far from settled. Curiously, Morgan generally ignores the bonobo and it’s face-to-face mating habits, even in her later books. She’s clearly aware of these apes (she does mention them and one graces the cover of The Descent of the Child), but they are conspicuously absent from discussions about sex.
Still, if we are to follow Morgan’s model, the apes would have to switch from mating using a rear-mount position to face-to-face (the males, we are told, couldn’t penetrate any other way), such a position causing much trauma for females. Males wouldn’t know how to calm the female for a face-to-face encounter, and it essentially led to either rape or an unfruitful attempt to mate. Morgan describes such a scene;
The primate was a totally different shape. Her new aquatic streamlining had been unable to prevent her becoming lumpy in the middle, and as a littoral biped her legs were developing in the opposite direction from the seal’s – they were becoming not smaller and thinner but farther apart, but longer and thicker and closer together. The seal’s solution was impossible for the aquatic apes. Their dilemma was unique.
So we left her on her back, kicking and struggling and frightened out of her tiny anthropoid mind, with her mate beginning to get irritated. When she saw him snarl and bare his canines she was finally convinced that he wanted her for dinner, and that her last hour had come. Further resistance was useless. She stopped fighting and signaled her submission, defeat, and appeasement as strongly as she could with so little room for maneuver.
Immediately, the incident was over. The male was a properly programmed animal, and it was impossible for him to go on clobbering a member of his own species that was giving clear indications that it had stopped fighting back. He moved a little way off, wearing a puzzled expression. He had thought for a moment that he was on to a good idea, but obviously there was a snag to it.
Such events removed us from our Eden along the shores, males taking up hunting on the plains soon after the eviction. Rains that quenched the African drought allowed the apes to leave the habitat that they had become so accustomed to (it seems like the males led the charge, being sick of their prolonged day at the beach), moving on to evolve in ways that fit the scientific orthodoxy of the times a bit more closely. Even so, Morgan suggests that women have retained the peace, beauty, and grace of their aquatic origins while males are more shaped by violence and hunting, her parting words being;
He is the most miraculous of all the creatures that God ever made or the earth ever spawned. All we need to do is hold out our loving arms to him and say: “Come on in, the water’s lovely.”
Oddly enough, such arguments seem more specific and in-depth than those in Morgan’s later works The Descent of the Child (1995) and The Scars of Evolution (1990). The Descent of the Child can largely be ignored, being that it’s primary focus is on doing for human babies (from conception through early childhood) what The Descent of Woman did for women, all-in-all being a string of facts presented to the reader in an easy-to-digest manner but without much further discussion. In covering past evolution, the “savanna hypothesis” and “man the hunter” are both alluded to or pointed out to be wrong, although no rigorous refutation is made. Instead the reader is referred to the earlier The Scars of Evolution for the “scientific” argument, but Morgan’s earlier poetry contains far more detail than the 1990 work. I breezed through the 178 pages of the book easily enough, but there was little positive evidence within it’s pages for the AAH. Certain physiological systems were pinpointed and deemed to be of aquatic origin since Morgan deemed no other hypotheses to be adequate (which, of course, assumes that all possibilities have been discovered and have received proper consideration).
I actually would love to write up a longer discussion of The Scars of Evolution but there is surprisingly little actual AAH evidence to be considered, and Morgan even makes some fairly basic mistakes about fossil preservation. Early on in the book she writes;
So if the prospecting had started in the north [of the Rift Valley] and worked down, popular illustrations of groups of Australopithecus would have shown them reclining under a shady tree at the water’s edge, living perhaps on fruit and greenery and fish. Instead, they are depicted as shaggy creatures trekking through parched grass and a scatter of stunted thorn bushes, turning to scavenging and hunting to supplement their diet.
This conclusion comes from Morgan’s assertion that some specimens of Australopithecus are found associated with fossils like crocodile remains and turtle eggs, suggesting an aquatic habitat. This largely ignores taphonomy, however, and an animal that dies in or near water being much more likely to be preserved and fossilized than one that drops out on the plains, the body undoubtedly being ripped apart by scavengers and leaving little or nothing to the fossil record. Most of the rest of the book covers material already mentioned in The Descent of Woman, like the fallacious notion that pheromones are essentially nonexistent or non-influential in humans because we went through an aquatic phase of evolution where scent wouldn’t have counted for much. Also curious is one of Morgan’s final statements about how evolution works, especially in regards to water. Rather than gaining specializations mentioned in so many of her works (i.e. the ability to cry and remove saline from the body, nostrils with possible flaps to keep water out, enlargement of the female breasts), a kind of de-volution of our ancestors is favored;
Conceivably, a species finding itself in a radically new environment (such as water) begins to shed the more advanced features which fitted it for its old environment. It back-tracks to a more unspecialized foetus-like form, before re-adapting to the new habitat. If that were the case, then our own ancestors, having moved from the land to the water and subsequently from water to land, would have been subjected to an impetus towards neoteny on two successive occasions. It would explain why in our case the trend was unusually powerful.
In all, Morgan’s work seem to be lacking of any rigorous research or hypotheses, and it led me to wonder why the AAH will simply not go away. Perhaps some of it is the mental appeal and the common error of linking correlation in evolutionary convergence to causation, working backwards to whatever ideal we hold most dear. Even if I’m incorrect as far as social motivation goes, the AAH has shown up in the scientific literature in the past few years, and it’s primary advocate seems to be Marc Verhaegen. Although the majority of his papers seem to be currently unavailable online, there is no name that more frequently appears in terms of AAH literature in scientific journals, giving the hypothesis some visibility (and credibility, as far as AAH advocates may be concerned). Some of the papers published on the AAH I could find are;
Bender R, Verhaegen M, & Oser N. “Acquisition of human bipedal gait from the viewpoint of the aquatic ape theory” Anthropol Anz. 1997 Mar;55(1):1-14.
Cunnane, S.C. “The Aquatic Ape Theory reconsidered” Medical Hypotheses Volume 6, Issue 1, January 1980, Pages 49-58
Ellis, D.V. “Wetlands or aquatic ape? Availability of food resources.” Nutr Health. 1993;9(3):205-17.
Rhŷs Evans, PH. “The paranasal sinuses and other enigmas: an aquatic evolutionary theory” J Laryngol Otol. 1992 Mar;106(3):214-25.
Vaneechoutte, M. ” Report of the Symposium ‘Water and Human Evolution’, Gent, Belgium, April 30th 1999” Human Evolution. 2000 Volume 15, Numbers 3-4
Verhaegen, M.J.B., Puech, P.F., & Munro, S. “Aquarboreal ancestors?” Trends in ecology & evolution (Amsterdam). 2002 Vol. 17, Issue 5, page 212
Verhaegen, M.J.B. and Puech, P.F. “Hominid lifestyle and diet reconsidered: paleo-environmental and comparative data” Human Evolution. 2000 Volume 15, Numbers 3-4
Verhaegen, M.J.B. “The Aquatic Ape Theory and some common diseases”. Medical Hypotheses
Volume 24, Issue 3, November 1987, Pages 293-299
Verhaegen, M.J.B. “The Aquatic Ape Theory: Evidence and a possible scenario“
Medical Hypotheses Volume 16, Issue 1, January 1985, Pages 17-32
Verhaegen, M.J.B. “Aquatic ape theory and fossil hominids” Medical Hypotheses Volume 35, Issue 2, June 1991, Pages 108-114
Verhaegen, M.J.B. “Aquatic ape theory, speech origins, and brain differences with apes and monkeys” Medical Hypotheses Volume 44, Issue 5, May 1995, Pages 409-413
[And for an opposing view see Langdon, J.H. "Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis" Human Evolution. 1997, Volume 33, Number 4, pp. 479-494(16)]
As is immediately apparent, the great majority of the papers have appeared in one journal (Medical Hypotheses) and can be attributed to one author, Verhaegen. Judging from what I was able to find, many of the arguments that Verhaegen employs are very similar to those of Morgan, working backwards from somewhat contested or enigmatic human features to an aquatic origin to the exclusion of other hypotheses. Where Verhaegen differs, however, is that his aquatic hypothesis is far more broad than that of Hardy or Morgan. While Morgan implied that the aquatic apes were an isolated group that ended up leading to man (what happened to populations elsewhere is never spelled out), Verhaegen suggests that the last common ancestor of living gorillas, chimpanzees, bonobos, and humans was at least semi-bipedal and semi-aquatic, likely living in a habitat like a mangrove swamp. From the paper “Aquaborel ancestors?”;
A vertical posture and an ability to climb with the arms raised above the head could have helped a wading primate to enter or leave the water by grasping overhanging branches or waterside vegetation, and to grasp fruits above the water. Body enlargement and tail reduction would hinder agile arborealism, whereas a larger body is more easily supported in water and helps reduce heat loss (explaining why aquatic mammals are larger than related terrestrial forms). Tails would be of little use for a wading and/or swimming primate and would cause both drag and heat loss.
Thus Verhaegen attempts to separate New and Old World monkeys from apes by making the ancestors of all living apes at least partially water-bound, standing up to wade through water. Ultimately humans would have stayed in the pool while gorillas and chimpanzees got out, although gorillas, chimpanzees, and bonobos do not seem to show the same signs of being adapted to water that are often associated with humans under the AAH. Of further note is the fact that living primates like baboons, macaques, and proboscis monkeys have been known to swim and stand upright in water, although none seem to show signs of becoming exclusively adapted to an aquatic lifestyle. In the recent BBC series Planet Earth, baboons of the Okovango Delta in Botswana were shown wading through the water;
The baboons are not especially comfortable in the water, just as many other animals in the delta like cheetahs and lions don’t especially like crossing the waterways. Indeed, crocodiles are the primary danger in the water, and many animals seem to know of the threat all too well (but must cross from time to time, anyway). Such modes of moving through water, also seen in chimpanzees (see the final episode of the BBC’s Life of Mammals, entitled “Food for Thought”), seem to constitute the “weak” version of the AAH, and isn’t entirely unreasonable in explain possible motivation to become bipedal. It does require a certain ecology, however, (i.e. flooded plains, a swamp, shallow mangrove forest, lagoon, etc.) and has little explaining power out of such a context. Still, there are even more aquatic primates that were also featured in Planet Earth; the crab-eating macaques.
If we’re looking for a model of what an aquatic ape would look and act like, surely these monkeys would be it, and Morgan does note some of the aquatic habits of macaques (especially the behavior of washing food in water, as seen in Japanese Macaques). The problem is that macaques are monkeys, not apes, although they seem to get along in the water just fine. Unfortunately the adaptation of these primates to water is going to be slow and take many generations, but the study of these animals could give us some clues as to what the AAH can and cannot explain, although it seems that many of the features explained by the AAH don’t fit with what we see in the macaques. Looking at the underwater behavior, it would seem that the monkeys would be adapted to swim in a matter similar to that of quadrupeds rather than to start wading in, becoming bipedal, and then doing a breast-stroke. Indeed, the video shows that becoming bipedal is not a necessary precursor to being able to swim or becoming semi-aquatic, and it is quite possible (even probable) that primates could abandon the upright stage altogether. Standing upright seems to be generally uncomfortable for many primates, and it’s hard to see how primates introduced to a fruitful aquatic habitat would want to stand up before just jumping in if there was really nothing to fear in the waters. Even in the weak version of the AAH, it is hard to see how standing upright while crossing a river would have selected for bipedalism as it seems that many primates are capable of doing it over short periods and it does not hold any strong advantage that would relate to mating success or overall survival. Unless the hypothetical apes lived in an area constantly flooded, requiring them to stand up much of the time, it is difficult for me to imagine how water could have helped to select for an upright posture.
The overall problem I have with Morgan’s hypothesis about apes becoming almost exclusively aquatic is that it forces us to make a choice of one habitat or another. Mentions are made of Proboscis Monkeys and Macaques enjoying a swim, washing off food, or living near water, but they don’t seem to be bent on the same path as the one Morgan proposes. Organisms certainly are plastic, and they don’t rigidly abide by the “rules” set down by those that describe them as to where to live, what to eat, and how to act properly. In fact, it seems more reasonable to me that primates past and present would take advantage of an aquatic resource if readily available, but still maintain their terrestrial life unless they were so isolated that they had no choice for food other than the water. Time will tell if some of today’s semi-aquatic primates ever become more fully at home in the water, but I see no reason to believe that our ancestors decided to take a prolonged summer vacation on the beach, proceeding in a way that just so happened to explain everything neatly (if un-parsimoniously).
The AAH hinges on apes willingly going into the water for safety from predators, but this is only a Just-So story without the details. It also ignores the fact that the water can be almost as dangerous, if not moreso, than the land, and there are predators in the water just as there are in terrestrial habitats, not to mention rip-tides and other problems inherent to the ocean itself. While Morgan, in The Descent of Woman, states that newborns could be left to paddle about on their own while mom went about her own business, such maternal inattention doesn’t seem like it would be especially effective in making sure that young made it to adulthood. Only the calmest, most sheltered, and safe of lagoons would have allowed for this. If the AAH is to be taken seriously in whatever form, it is going to require rigorous ecological study, and so far it seems that it relies far more on post hoc arguments than actual evidence.
While Jim Moore has already done a fantastic job dismantling the various problems with the AAH, I hope I have helped to illuminate the overall lack of evidence for the idea. As an idea it’s not a bad one, but it seems to have never gone beyond hypothetical situations and Just-So stories, and most of the ideas associated with the AAH seem to be criticisms of other hypotheses, therefore leaving the AAH as the only alternative. While I can certainly appreciate the frustration Morgan and others must have felt (and even still feel) towards a male-dominated field in science and consideration being mainly given to the strong, archetypal male, I feel that the AAH is taking things too far in the other extreme. It is hard to ignore the feminist underpinnings of Morgan’s writing and the overall disregard for the big picture in order to bring women and children into closer focus. Combating a hypothesis you don’t like with an equally narrow one, just reversed, is not the way to bring greater understanding of our evolutionary history, and given that hominids and apes are so close to us, it’s easy to fall into trapping of preference. Being that I am no expert on the matter, however, I will close with T.H. Huxley’s final words from his work Man’s Place in Nature, as they seem to resonate with the big questions about our origins that remain unknown;
Where, then, must we look for primeval man? Was the oldest Homo sapiens pliocene or miocene, or yet more ancient? In still older strata do the fossilized bones of an Ape more anthropoid, or a Man more pithecoid, than any yet known await the researches of some unborn paleontologist?
Time will show. But, in the meanwhile, if any form of the doctrine of progressive development is correct, we must extend by long epochs of the most liberal estimate that has yet been made of the antiquity of Man.