Anthroposaurus
The Aquatic Ape: Did Humans Evolve in Water?
Abstract
Contents Updated: Wednesday, December 15, 1999
We know the way to heaven to be as ready by water as by land.
Submergence Convergence
Land animals quite commonly return to the water just as birds sometimes become flightless. Herr Hauff’s ichthyosaur evolved from an ancestor that returned to the water over 200 million years ago. In the last 80 million years mammals have often entered the water, found it comfortable and stayed.
The cetaceans, the whales and dolphins, were the first to do it. Little rat like creatures like all mammals then, they sought to avoid the terrors of the dinosaurs by hiding in the water of river estuaries. It was safer, they stayed and gradually adapted to their new surroundings. The buoyancy and safety afforded by the water allowed them to grow bigger and eventually take to the open sea, especially after the great carnivorous sea dinosaurs had all died. Today they are supremely adapted to the aquatic environment. But occasionally a throwback will reveal something more of the original land mammal.
Some hoofed mammals paddled into the water 50 million years ago to become the dugongs and manatees. About 25 million years ago, a bear like creature took to the water to evolve into sea lions and at the same time some dog like mammals immersed themselves to become today’s seals. More recently we have seen otters of the stoat family adapt to the water, beavers (a rodent), the hippopotamus only 5 million years ago. And… a certain ape?
Although most zoological orders can boast some representative that has fully adapted to water, the order of primates cannot.
Sir Alister Hardy proposed to change that by suggesting in 1960 that many of man’s peculiar features could be explained if an ancestor had adapted to an aquatic or semiaquatic life for a few million years before emerging again equipped to conquer the world. Hardy’s theory, though gaining adherents, is not regarded as respectable in most anthropological quarters but, if an ape did submerge, there was a very good reason and a likely place for it to happen. More of this toward the end of the chapter.
A few million years in the water give us convincing explanations of otherwise untypical and inexplicable human characteristics, including some of the those we have been looking at. Why are we bipedal? Why are we naked? Why do we have a layer of subcutaneous fat? Why do we possess the diving reflex? Why can young human babies swim before they can walk? What triggered off speech?
Writer, Elaine Morgan, expands on Alister Hardy’s idea in her book, The Aquatic Ape, in which she makes a compelling case for the aquatic hypothesis. She takes questions like these and attempts to answer them from the physiology and behavior of known aquatic animals. In other words she uses the principles of convergent evolution—human adaptations typical of aquatic animals suggesting an aquatic origin for humans.
An animal in a given environment is faced with a set of evolutionary problems. To resolve these, it has a limited number of efficient solutions—there are only certain routes in the evolutionary landscape that are feasible. Anteaters, pangolins and aardvarks, all having the same type of lifestyle, have developed the same characteristics, long snouts, strong claws and sticky tongues, to let these creatures dine on colonies of insects. By looking at the common features of these creatures one can deduce that they have similar habits. Their similar solutions to the problems of their environment suggest that environment. If we see an animal with a set of characteristics usually acquired in an environment different from its own, it seems reasonable to deduce that the animal has at some time experienced the environment which gives rise to its peculiar characteristics. The arguments for human origins as an aquatic ape are therefore instructive, highlighting convergence and the features which make us singularly human, but I shall give them very tersely to avoid delay in my own arguments.
Humans are the only mammal habitually to walk on two legs, though some others do occasionally. Grassland animals like the vervet monkey, the rabbit, the meercat and the gopher stretch upright to look around for danger but, if they see any, they run off on all fours. Why don’t they stay upright as man has done?
In 1970 C.R.Taylor tried experimentally to show the relative energy cost of walking on two or on four legs. Initially he announced that bipedal walking was twice as expensive in terms of the energy needed. Owen Lovejoy was right—walking bipedally is “preposterous!” Not so. Later, more accurate experiments contradicted Taylor’s initial assessment. They still favored four legs but in a more subtle way. The energy cost did not materially differ for two legged and for four legged locomotion. But, for the same energy output, animals could move much faster on four limbs than they could on two. It looks unlikely that a slow, ungainly tree dweller could succeed in the world of fast moving grazers and predators by attempting to walk upright. Not that a bipedal creature cannot compensate for the speed of its four legged competitors, our own dominance of the world is proof enough of this—the advantages conferred by two legged walking plainly have overcome the advantage of speed—but how could the tyro bipedal ape learn the skills he needed before he got eaten by the fast four legged hunters?
The protagonists of the aquatic ape theory are not convinced by the scenario of the savannah ape. They argue that the ape had to have the safety of some haven from the predators to learn how to stand upright and water provided that haven for mankind just as it had for the ancestors of whales and seals. Wading out into the sea to search for seaweed or shellfish is a safe and natural way to become upright. Macaques, those widespread, intelligent and alert monkeys, seem to be broadening their response to their environment even as we look on. Crab eating macaques are one of the few primates that do not fear water: they wade out into the sea to catch their crunchy prey. Japanese macaques, we saw, discovered how to wash sandy potatoes in the sea, wading out on their hind legs while holding the potatoes. If these animals were to wade out of their depth they would find that they floated upright quite naturally—as a man does.
Beavers, having got used to an upright position when resting in the water, find it useful sometimes to walk on their hind legs when carrying their young or materials for dam building. Many sea mammals habitually float upright in the water—like the manatee. Female manatees have rounded, human looking breasts and sit upright in the water cradling their young in their “arms” whilst suckling them. Steller’s sea cow behaved similarly before men hunted it to extinction. These are the only other mammals to have developed anything like human breasts. Seen from a distance bobbing upright in the water with their breasts exposed, sometimes with a baby in their arms, perhaps draped in the weed upon which they fed, they excited the imagination of lonely sailors and gave rise to the legend of the mermaid.
When swimming, however, these creatures launch themselves horizontally. A creature that walks on two legs, the penguin, swims horizontally and another creature that walks on two legs also swims horizontally—man. The effect on the seal of adapting to the horizontal swimming position was to swing its pelvic girdle parallel to its spine. The same transformation has occurred in man! The human body is remarkably streamlined, and any moving picture of humans swimming underwater shows immediately how graceful we are in the water. It is the need for streamlining in the relatively dense medium of water that forces a bullet shape on to animals which are habitual swimmers—mankind has been no exception.
A consequence of this streamlining is the necessity to copulate in more convenient ways than the normal rear mounting method of most mammals. Man is the only great ape to copulate face-to-face, yet the majority of marine mammals do so. It has required the human female to orient her sexual canals towards the front. Female foetuses of apes, but not adult females, have their sexual canals oriented towards the front. Human females carry this feature into adulthood. Such a change, foetal or infantile characteristics taken into adulthood, is called neoteny.
Amphibians begin life in the water as tadpoles but as adults spend most of their time on land. But a Mexican salamander found life in the water more comfortable than the struggle on land and a neotenous change occurred to adapt it for such a life. It kept all the features of its tadpole stage into adult life and actually breeds and lives its whole life now as a large tadpole. It is the axolotl. We know for sure it is a neotenous salamander because it can be induced to undergo the metamorphosis that it normally postpones for life and the result is an ordinary looking salamander.
Neoteny is a mechanism for rapid adaptation to changing conditions and succeeds because juveniles are usually less specialized than adults. A minor change to a gene controlling development is all that is needed to delay growing up.
It seems to have worked strongly in man’s evolution. Those who dislike the aquatic theory say that neoteny is all that is needed to explain the changes in the developing ape. If so, what unusual conditions required neotenous changes in an ape setting out to explore the grasslands? Evidently none. The baboon successfully made the same transition without invoking neoteny. Indeed its snout lengthened compared with an ordinary monkey rather than remaining flat like the foetal baboon’s. Nor did they lose their body hair as mankind did. Admittedly, man is not really the “naked ape” because he has as many hair follicles per unit area as any other great ape. Human beings look naked because human hairs are so short and so fine that, to all intents and purposes, human beings are naked. Why should a savannah ape be effectively naked? What is the reason for human nakedness?
Some anthropologists argue that by shedding hair our ancestors were able to keep cooler whilst hunting. Who then did the hunting? Human females? Female humans have lost more hair than male humans. And if nakedness solved the problem of overheating, why did other mammals not adapt in the same way? Other primates which took to the grasslands when the Miocene forests retreated, like vervet monkeys as well as baboons, did not find it necessary to lose their hair. Indeed, why, if nakedness is held to be such an advantage, do many humans, like the bedouin, cover their skins with wrappings of loose cloth in strong sunlight? Hair protects the skin from direct solar radiation and it also acts as an insulator, by trapping air, keeping its owner warm on cold savannah nights. Hairless humans have to use warm blankets at night to substitute for their ineffective hair. It is strange for any creature of the savannah to be bald unless they have thick skin like the elephant or the rhinoceros.
Other savannah theorists sidestep this reasoning, accepting that nakedness was disadvantageous but arguing that neoteny nonetheless effected the change because the advantages outweighed the disadvantages. The foetuses of great apes are, at one stage of their development, naked. A trigger is needed for neoteny to have occurred but it was not entering the water—it was to accommodate the human learning experience. Maturity was delayed so that an extended childhood could fill the growing brain with knowledge and experience. Gestation, childhood and progress to maturity slowed down relative to other primates; childhood features were retained including childhood curiosity which gave humans the incentive to learn late into their lives. The extension of adult life also meant that parents survived long enough to protect and teach their slow maturing offspring. But neoteny cannot choose the good features of the infant to extend into adulthood and leave unchanged the others. The whole gamut of juvenile features have to be carried into adulthood. Though hairlessness was disadvantageous, the package was advantageous overall and was selected by natural selection.
But this whole notion is easily disproved, first by the success of other primates successfully stepping on to the grasslands at the same time without recourse to neotenous changes, and second by the lanugo of human babies which is overlooked by the savannah theorists. The lanugo is the hairy covering that human foetuses have before birth. They start to become hairy but the hair regresses, and by birth has usually gone, though, on occasions it is retained for a while after birth, to the horror of some parents. The neotenous changes envisaged by the savannah theorists would surely have favored selection of the lanugo to continue into adult life to protect the hominid’s sunboiled skin and retain warmth in the cool nights. We should quickly have been no longer the naked ape. The failure of the lanugo to evolve as a protection shows that human nakedness evolved as a positive response to some situation. Living in water was it.
Creatures which commonly do lose their hair, quite naturally because it is favorable to their evolution, are animals that spend all or part of their time in water. The longer the evolutionary period they are immersed, the more likely they are to be bald. The hypothesis of the aquatic ape is that mankind is naked because we lived for several million years as partly aquatic creatures. The hippopotamus which evolved at about the same time as man, only five and a half million years ago, is naked, though it does not spend its whole time in the water. It emerges, usually at night.
Fur is primarily a heat insulator to retain the warmth of the warm-blooded mammals, though strictly it is not the fur itself which insulates, it is the air trapped by the fur. Wet fur is useless as an insulator. The trapped air is replaced by water, a better conductor of heat, which renders the fur ineffective. Hair also slows down a swimming animal because it creates friction in the denser medium. Though humans are hardly hairy, this friction can be so crucial that swimming champions shave their body hair before a race to gain a fraction of a second on less competitive rivals who have not bothered.
Mammals that have retained hair despite living in water return to the land to breed and live in colder northerly climates where their fur is still useful for insulation when the animal is out of the water. Seals, sea lions, beavers and otters are in this category.
So, human hairlessness can be explained by a few million years’ dip. But why do humans, especially human females have thick hair on their heads? Because hair on the scalp served as protection against the tropical sun when the apes were floating upright in the water. Their naked bodies were protected by the water but not the tops of their heads. A woman’s hair tends to be more permanent than a man’s, but more interesting is that it gets stronger and thicker in pregnancy. Elaine Morgan believes aquatic children needed to hang on to their mothers in the water. Baby monkeys cling to their mother’s fur, but if all the hair had gone from the aquatic ape its baby would have been in trouble, instinctively trying but failing to cling on to smooth slippery skin. What is more natural than scalp hair, retained to prevent burnt heads, providing an anchor for babies?
Hairlessness could have served to allow the hominids and the australopithecines to distinguish themselves when the two lines were still evolutionarily and geographically close. Those in the hominid line might have selected sexual partners that were hairless while, in the other line, hairiness might have been the factor chosen. Each would find the appearance of their close relatives repugnant. This is sexual selection. Darwin recognized it as being an important selection mechanism.
But Morgan argues that sexual selection in favor of a feature can occur in a species only when that feature has already become established for other reasons. Once the aquatic ape became naked through cavorting in the water, sexual selection would ensure that nakedness continued. In like manner, the aquatic apes would not regard the retention of scalp hair as ugly. It would be regarded as a supremely attractive feature. Nowadays men and women alike regard women with beards with fascination and horror, but they admire beautifully coiffured scalp hair on women. Smooth skin in a man is not regarded by women as ugly, perhaps the opposite, but a bald pate they often think is unattractive—on women, generally admired for their smoothness, it is worse.
These instances seem illogical unless sexual selection in the aquatic context is considered.
Frowning is a peculiarly human habit, explained by the aquatic hypothesis as a response to the sun’s glare from the surface of the water. But, except in their faces, humans have largely lost the muscles which move their skin. Vestiges remain in phenomena like scalp hair standing on end through fear, and cold causing goose pimples, but we have nothing like the ability cows or horses have to shake off flies by vigorously twitching their skin. The skin muscles were lost along with hair because moving hair was their main function: no hair, no skin muscles—they had become redundant.
The retention of muscles to move the skin in the face is connected with visual communication. Animals floating upright at the water’s surface only had their faces exposed. Interpretation of subtle facial movements therefore took on special significance. The expression of emotions via facial expressions would have been especially important as social structure evolved.
A layer of fat underneath the skin is a much better insulator than fur for a warm-blooded water dweller. No primate has it—except man. It is another peculiarly human feature. Some other terrestrial animals store fat but rarely under their skin. Humans are born with a fat layer. Human babies are unusually rounded, and heavier than the babies of the great apes. A human baby is almost twice as heavy as a baby gorilla or chimpanzee though human adults are lighter. According to the aquatic theory, besides providing necessary insulation to the baby this fat was a vital aid to buoyancy.
Other mammals besides man have sweat glands which they use for excretion of wastes. Man is unusual in having exceptional numbers of them, and in using them as a way of keeping cool. Sweat cools by taking away body heat as latent heat of vaporization. It requires free access of air to the skin since air trapped near the skin soon becomes saturated in moisture. Further evaporation then stops and sweating no longer works. Hairiness stops sweating from being efficient as a cooling system. No great ape, other than man, sweats to keep cool. It would be inefficient if it did.
But for sweating to evolve as a means of keeping cool on dry or even arid grasslands is absurd—it drains the body of essential water and salts. And it would be suicidal for any ape to opt for a water cooling system where water is at a premium—on the dry grasslands. A man walking naked in the tropical sun at 100 degrees Fahrenheit (40 degrees Celsius) can lose up to 28 liters of fluid and an eighth of his body’s salt a day by sweating. For urination only one liter is needed. It is plain nonsense to postulate that the savannah ape first lost its hair to keep cool, then put on a subcutaneous layer of fat to keep warm and finally developed a life threatening system of sweating to keep cool again. The only way to make sense of such a ridiculous sequence is the aquatic hypothesis. The first two stages, hair loss and the evolution of a fat layer instead, were adaptations to living in water.
Sweating served two purposes. It was a way of ridding the body of surplus salt ingested while foraging in the sea. And it was a natural way of allowing a water ape to keep comfortable when out of the water by taking a little of its environment with it. The loss of large amounts of water would not matter if a water supply is always nearby, and so aquatic apes would not have willingly moved away from their water source. Their gradual re-adaptation to the land would have been by them staying close to rivers and lakes and moving inland only as their sophistication grew.
We have seen how close we are to the chimpanzees in terms of DNA. We are also similar in our thought processes. Chimpanzees have a wide range of emotions and have sufficiently mobile faces to show them. But when distressed they do not cry, simply because they cannot, despite their evolutionary closeness to humans. Only elephants and humans of land animals express tears. All other animals that weep are aquatic. (And there is a lot of evidence that elephants were aquatic at some time long ago!) It is a poignant sight to see a baby seal after its mother has been clubbed to death by a human with a baseball bat, weeping on the ice floes before it too has its skull crushed, killed to gratify human vanity.
Birds, particularly marine birds, have nasal glands behind their beaks to get rid of excess salt, but these birds also get a wet beak from the salt gland when they are excited or emotionally aroused. They are crying. Other marine creatures such as the marine turtles, marine iguanas and terrapins have similar glands. Crocodiles do cry crocodile tears but only the marine variety, not river crocodiles which do not have to cope with salty water. Many dinosaurs had spaces in their skulls in front of their eye sockets and these are thought to have housed similar salt glands. So it is possible that some dinosaurs also cried. The connection of tears with the salt gland and the sea seems obvious, even if its original use is no longer applicable. Only the idea of the aquatic ape can begin to explain a human’s ability to cry.
Marine mammals have a most valuable reflex action when they go into a dive. Since they cannot breathe while underwater, they have to conserve oxygen. Their heart beat therefore automatically slows down. This is the diving reflex. Animals that are best adapted to the water, like the cetaceans, show it strongest, and, as far as anyone can tell, the reflex is not present in terrestrial species—though any poor creature thrown into deep water is likely to miss a heartbeat or two, so experimental results are not always conclusive. But, although man is terrestrial, he has a noticeably effective diving reflex. The heartbeat of a diving human slows down to half its normal rate of 72 beats per minute. This is an odd adaptation for a land animal!
Since the diving reflex is a mechanism for coping with a deficiency of oxygen, it has another aspect. It preferentially supplies oxygen to the brain which is soon damaged by lack of it. To do so more robust parts of the body are deprived of oxygen. This explains how people can sometimes be resuscitated after apparently drowning, especially in cold water, without suffering brain damage. Not all adaptations to diving have proved beneficial to mankind. Asthma is unknown in apes but in humans it mimics the constriction of the bronchial tubes in a diving seal. Diving is, of course, a stress. Asthma looks like a partial adaptation to diving that now manifests itself not under the stress of diving but under the different kinds of stress to which modern humans are subjected.
Human noses are also partially adapted to an aquatic life. They have become narrow, are supported at the tip by a bridge of cartilage, and have nostril flaps with muscles allowing them to be flared. A seal’s nostrils have similar muscles that are relaxed when the seal is submerged keeping its nostrils closed. On surfacing the muscles flex and the nostrils open to let the seal breathe. Plainly human forebears had begun to evolve the same means of preventing water from entering their breathing tubes.
Besides their developing ability to close their breathing tubes externally via the nostrils, humans can also block their nasal passages from their throat at will. This aspect of the aquatic adaptation has become an essential feature of speaking. It allows a subtle control of the expulsion of air over the larynx without which speech would be impossible. Thus the control of breathing required by a diving animal has helped humans to develop the power of speech by controlling the passage of breath through the larynx.
Rudimentary webbing can be seen between most people’s fingers and especially between the thumb and forefinger, but in about seven per cent of people it is pronounced enough to be regarded as ugly. Why should a line of mammals that have spent 60 or 70 million years in trees show even the slightest trace of webbing, an aquatic adaptation? There is no reason. Webbed hands are useful only for swimming.
Water compulsively attracts human babies. If babies younger than ten months old are put on a gentle slope leading into water they show every sign of being fascinated by this beautiful wet stuff. They explore the new medium, venture into it, show no signs of fear or panic, gaze about in wonderment with their heads underwater, are naturally buoyant, naturally hold their breath for long periods, naturally adopt a swimming position and quickly learn how to swim. After ten months these instincts are lost, the breath control goes because the child has not had cause to develop it. Older children and adults have to be taught how to swim.
Babies have been happily born underwater with apparent benefit to mother and child. Furthermore all terrestrial female mammals, even those that do not eat meat, eat their placenta after childbirth. Human mothers do not, and don’t seem inclined to, even if primitive or starving. Aquatic mammals also do not eat their placenta. They have lost the instinct simply because, after the aquatic birth, the afterbirth floats away to be lost while the mother is ministering to the needs of her new born child.
The coordination of group hunting as the drive behind the evolution of speech does not hold water. Mammals like wolves, hyenas and lions hunt cooperatively but have not evolved speech. Watch humans hunting. Far from shouting to each other they communicate by visual signals so as not to forewarn the game (or, in warfare, the enemy). Other than man the creatures that have developed vocal communication furthest are the whales and dolphins. The reason is that visual communication is hampered by the water.
Dolphins have a wide range of sounds, many being whistles. If two dolphins start whistling at the same time, one will stop until its companion finishes, then it will resume. It seems as though they are taking it in turns to listen to each other and to speak—they seem to be conversing. But is there any proof? In behavior experiments, dolphins are not allowed to see each other but are allowed to hear. Yet if one is shown a lever to press to get a reward the other one knows too. They seem to be telling each other which levers to press to be rewarded. Richard Mark Martin concludes:
Tasks… were accomplished by the dolphins with so much assurance that it was obvious they did indeed have a language…
Humpback whales, which can articulate about 20 different sounds, are so sophisticated in language that they “speak” in rhyme. Two US researchers, Linda Guinee and Katherine Payne, came to this conclusion after listening to countless hours of taped humpback whale sounds. A third of the whales’ song consisted of rhyming sections. Consecutive passages tend to end in similar sounds even though the rest of the song is quite different. Whales in one part of the ocean use the same rhymes but the rhymes change with time, showing that they are not instinctive like birdsong. Humans find rhymes so compelling that they cannot get certain rhymes and jingles out of their heads. Advertisers play strongly on this. Possibly the rhymes help the whales to remember the songs which act as social cement within the groups. For whales, the rhymes are most common in the more complicated songs—the ones most difficult to remember.
R.D.Martin suggests:
There might have been a close association between increasing locomotor sophistication and increase in brain size in primate evolution.
Yet in stepping down from a three dimensional life in the trees to a two dimensional life on the plains, surely opportunities for movement were lost, and with it locomotor sophistication would have been decreased. But if the ape first took to the water thus retaining a sense of the vertical while requiring the development of entirely new locomotor skills, Martin’s suggestion would have more validity.
Animals that take to water often have unusually large brain:body ratios. The talapoin monkey of Gabon is one of the few primates to have taken to water and it has a large brain:body ratio.
Stimulated in the trees, stimulated anew by the transition to water, stimulated again by a whole host of new experiences on moving permanently to the land, the human brain became sophisticated enough to develop, not only locomotor skills but speech, advanced toolmaking and a complex social life that might have had the biggest effect of all. Elaine Morgan concludes:
Many other primates have moved from the trees to the open plains, and in no single one of them has that move produced any of the changes that caused the ancestors of Homo sapiens to diverge so dramatically from all his nearest relatives.
Submergence convergence provides a more convincing explanation. That is the theory of the aquatic ape in a nutshell. It is not based on fossil evidence. Coastal waters and lowland swamps are not particularly conducive to fossilization. Sharks, crocodiles and crabs would see to that. It is entirely deduced from structural convergence as a plausible explanation of the peculiarities of our species of ape—and the coincidence of suitable geological events.
According to the aquatic theory, a period of immersion for mankind’s rootstock produced adaptations that now characterize mankind and differentiate them from their brothers, the apes—loss of body hair, subcutaneous fat, bipedalism, face-to-face sex, sweating, tears and speech. Though not all man’s characteristics should be attributed to the aquatic phase, long legs in humans have mainly evolved in the last four million years while the hominids have been walking on land. Lucy had quite short legs.
Why should all this be?—most primates hate water. Gorillas do so to such an extent that a shallow moat is all that is needed to keep them confined. How is it possible that strong adaptation to water occurred? Why should our predecessors have spent a lot of time in it? Where and when did the pre-hominid apes take to the water?
When?
When the sea level rose flooding the sea margins. The apes had to adapt to water as the lowland forests became swamps and islands, then coastal waters. Similar events in the past put whales, manatees and seals into the water.
Where?
Where a region isolated by the sea in the Pliocene was populated by apes in the Miocene. In the late Miocene, movements of crustal plates had opened the narrow but widening Red Sea. Africa and Arabia were still just connected by the Afar Isthmus between what are now Abyssinia and The Yemen.
The ape, ramapithecus, lived in Kenya from 14 to 12 million years ago and remains have been found in India dating from 12 to nine million years ago. For part or all of this time, ramapithecus must have lived near the isthmus. At the same time, crustal movements were thrusting up a portion of the earth’s surface to form the Danakil Alps. Then, sometime between 6.7 and 5.4 million years ago, the Indian Ocean broke through to the Red Sea flooding the Afar Triangle, where Don Johanson later found Lucy, leaving the Danakil Alps as an island.
Danakil island became an evolutionary forcing house for hominid development. From the end of the Miocene the climate began to become cooler and drier, killing off the forests of Danakil. The forest apes trapped on the island had to adapt to the water, if they had not already done so, because of the scarcity of terrestrial resources and to escape from predators which were better able to cope in the less dense bush of the thinning forests.
Present day talapoin monkeys have a strategy of dropping out of the trees into water at any sign of danger. When the lowlands flooded, perhaps the Danakil apes also took to the water by developing the habit of diving out of trees into the swamp or river.
In fact, the Danakil region was probably never a true island. The southern part was probably linked to the African mainland, but extensive volcanic action caused by the movement apart of the Nubian and the Arabian crustal plates created immense lava fields which would have been a daunting barrier to apes moving towards the mainland. But the eruptions would have been episodic: in the quiescent periods the apes might have had chances to escape. This could explain the apparent waves of new hominids appearing quite suddenly throughout mankind’s emergence.
In the first quiescent period some of the apes (A.afarensis) were able to cross to the mainland. Others remained behind still evolving. They (Homo habilis) were able to cross about 1.8 million years ago. Then about one million years ago more apes (Homo erectus) crossed. The cycle possibly continued until the region finally dried out about 30,000 years ago, explaining the successive waves of ever more advanced men coming apparently from nowhere and culminating in H.sapiens sapiens.
When the aquatically adapted apes, having escaped from Danakil, began to explore the hinterland, their need for water would have confined their range to waterways and lakes. Paleoanthropologists like Richard Leakey and Don Johanson have found fossil hominid remains in just such places. Four million years ago the emergent submergent apes were at Hadar where Johanson found his remains including Lucy. Later they were at Lake Turkana and Koobi Fori where Richard Leakey’s teams found their remains.
Hypervitaminosis A, a disease caused by an overdose of vitamin A was noted in some of Leakey’s fossils. Leakey’s interpretation was that the hominid had had too great a predilection for liver, but the richest source of vitamin A is fish, suggestive of a diet excessively rich in fish to which the ape had not fully adapted.
In the brief period since the forest ape took to the water, according to the scenario just described, not more than 6.7 million years ago, intelligence emerged. Geologically that is a short time. Can features evolve so quickly?
The answer is a categoric “yes”! Mechanisms have evolved which allow quite astonishingly fast evolution and there are probably more to be discovered. The next chapter shows that rapid evolution can occur. It has happened to mammals yielding mankind: it could have happened to the dinosaurs.
