Gnawing marrow-bones might get you through hard times, in evolutionary terms, but when you're looking for brain development, you're talking seafood.
Recent work by Finnish scientists has been widely accepted to show a link between Omega 3 fatty acids and brain health.
So much so that it has caused a kind of revolution in the food industry, much to the detriment of wild fish stocks worldwide.
Nutritionally, it's difficult to assert reasonably that an ape could, or would, adapt to a savanna lifestyle, newly dependent upon scraps left over from predator-kills, and in the process ingest enough fatty tissue to support the phenomenal cerebral expansion shown by the fossil record during the late Miocene in hominids.
We don't see a parallel to this in other primates which did (and do) occupy the savanna niche, for instance baboons, but we see a roughly equivalent expansion, although on a much different timescale, in aquatic mammals such as dolphins.
That's one of the arguments that make up the Aquatic Ape hypothesis, a kind of catch-all formula to explain the suite of derived characteristics that separate humans from our nearest biological cousins.
The idea was first offered in public by Sir Alister Hardy in 1960.
On March 5 of that year he appeared at the British Sub-Aqua Club at Brighton and presented a paper later published in The New Scientist, where he explained that he felt the moment was "appropriate." It's well worth noting that he waited until the end of his career as a marine biologist before such a moment came along--he had first been struck by the idea in the 1929, after an expedition where he spent a great deal of time dealing with seals and their subcutaneous fat.
Apparently, much of the delay was because he began lukewarm about it, but, "the more I reflected on it, the more I came to believe it to be possible, or even likely." (The New Scientist, Vol. 7, April 1960) He also hoped that fossils would be discovered in support of his idea although he noted that many of the most likely habitats are in modern times submerged by the Indian Ocean. In a 1977 article for Zenith, the magazine of the Oxford University Scientific Society, Hardy went into a little more detail: "So after some twenty million years or more of living a semi-aquatic life--I must make it clear that I do not suppose man spent more than perhaps five or six hours in the water at a time--Homo aquaticus left the sea (or lake) a very different creature from when he first entered it." Both Hardy and his protege, Elaine Morgan, emphasize the ready availability of fat-rich, easily gathered, perennial, rather than seasonal, food sources to be found in inland seas, estuaries and other bodies of water, a far cry from the nuts, berries, tubers and odd bits of meat available to the same animals on land. Readers of Elaine Morgan's books on the subject realize right away that she is looking at the problem in a different light.
In her first book, The Descent of Woman, she begins with a discussion, not of a brave male pursuing dangerous beasts, but of a resourceful female searching for shelter and a safe supply of food.
"She knew at once she wasn't going to like it there (on the savanna, when during a period of forest retreat).
She had four hands better adapted for gripping than walking and she wasn't very fast on the ground.
She was a fruit eater and as far as she could see there wasn't any fruit." Morgan was, of course, looking at the problem in slightly different terms than Robert Ardrey (The Naked Ape) and Desmond Morris (the Mighty Hunter Hypothesis) had done.
She was considering the possibility that the great evolutionary leap was prompted, not by the difficult route mapped out with males as the central figures, but by the more immediate needs of her own gender.
This may have been partly because, in 1972, women around the western world were questioning everything about a male-dominated society, and wondering whether there was a way to fit women into the evolutionary picture.
That it made sense was, perhaps, an unexpected bonus. During Hardy's time, the Mighty Hunter hypothesis was as solidly fixed in both the scientific and the public minds as it ever would be, although in recent years its many shortcomings have come under increasing scrutiny.
On the other hand, AAH, an apparently reasonable alternative, despite a 35-year campaign by Morgan, (who, with her popular books, has transformed AAH into a near-cult with all the faith-based restrictions of any shaky hypothesis), the scientific community is no nearer accepting the aquatic evolutionary phase of hominid history than it was a generation ago. Most texts and popular books which might most naturally mention AAH, if only to offer a refutation, fail to notice it.
It's far from forgotten, however.
Morgan who published The Descent of Woman in 1972, and followed that with The Aquatic Ape in 1982 and The Scars of Evolution in 1994, has refused to let go of the idea.
In fact, with the latter titles, she shows evidence of being more determined that ever to have the hypothesis taken seriously.
The books are widely read, and support a variety of websites devoted both to advocating and refuting AAH.
Not all of these are based on good science, or even good sense, but fundamentally the idea is hard to refute out-of-hand, if only because the recognized authorities, from whatever discipline they approach the question, still have significant disagreements to contend with when it comes to shadowy Miocene behaviors.
As far as drawing firm conclusions, the data available now--although certainly much more complete than Hardy had the advantage of--is still spotty.
As a result, the conclusions about such things as fossil dating and primate lineages are necessarily more in the form of conjecture, and one generation's firm conclusions are often the next's quaint misconceptions, neatly discarded, but replaced by more conjecture. Morgan, an Oxford graduate, is not and has never claimed to be a scientist, which could account for the code of silence around her books.
She writes for Welsh television, and the writing she's done on anthropology is of the easily-digestible type.
Whether or not that makes it less scientifically reliable isn't exactly clear. Milford Wolpoff of the University of Michigan, in a comprehensive 1999 text on paleoanthropology, never mentions the aquatic hypothesis at all, although he comes close.
In making his "Case for an Arboreal Ancestry," Wolpoff notes, "...if Oligocene genera such as Aegyptopithecus from the Fayum are ancestral to the living hominids, evidence of the fact that the Fayum was a swamp forest (my italics) then means these primates were arboreal." He goes on to wonder whether the common ancestor, from whom humans, gorillas and chimpanzees radiated, lived at ease in the trees like a gibbon or like a rather more tentative climber.
He isn't willing any longer to guarantee a brachiating ancestor, but some type of life in the trees is virtually certain. True brachiating is quite rare among primates, and doesn't occur among chimps and gorillas, which still enjoy comfortably arboreal lifestyles when it suits them.
Wolpoff keeps running into significant questions: "The morphology of the earliest known hominid hands and forearms is quite different from the ape morphology, and the question is why?
(his italics) (Paleoanthropology, Wolpoff).
The hands and shoulders of a human being are certainly no more than tenuously prepared for a committed arboreal lifestyle.
Even a trained gymnast would have trouble consuming a meal of fruit while suspended from a creaking limb by one hand.
For most humans the act isn't even worth the attempt. Coming up with an all-inclusive model for the scenario favoring the specific adaptations made in the human lineage is all but impossible.
It's made more difficult by Wolpoff because he seems determined to stick with Raymond Dart's "Killer-Ape" hypothesis at all costs.
Morgan, however, not only has an alternative, but can show us contemporary models.
"There remains the water theory.
The nearest primate model here is the proboscis monkey, which often resorts to bipedalism not from choice but by necessity. "In the award-winning documentary film Siarau (Partidge Films, Ltd.
1984), there is remarkably vivid footage of a band of these animals walking along on their hind legs, up to their chests in water." (Morgan) Not only does she show us bipedalism in an "abroreal" primate, she also ties the feminine aspect in by noticing a female proboscis carrying an infant through the water "the clasp and posture strongly reminiscent of a woman carrying a baby." (Morgan, The Scars of Evolution) Therefore, it's tempting to embrace AAH if only because it could potentially tie up so many loose ends: "If we regard the ancestral primate as an aquatic ape, he ceases to be a mysterious zoological aberration evolving unique and inexplicable features of no use to himself and highly deleterious to his children.
Put him among the aquatic mammals and he becomes a conformer, obeying the laws of evolution instead of running contrary to them" (Morgan, The Aquatic Ape).
Following up on Hardy, Morgan applies Occam's razor to the problem, reasoning that the simplest explanation may well be the best. Resistance to Hardy was quick to appear.
He reported in Zenith that he was "forced to publish it [the paper in The New Scientist] to protect myself from the outrageous distortions of my views that appeared unexpectedly in the national press." Ordinarily, one would expect such an all-encompassing solution to one of the great riddles of human history to be vigorously pursued, as Hardy hoped it would be, but, again, one searches the scientific texts mostly in vain. Two authors who actually mention AAH are split on their reaction to it.
John Gribbins and Jeremy Cherfas, in The Monkey Puzzle, put it this way: "One of us thinks that the best one can say of Morgan's version of Hardy's hypothesis is that it deserves to be taken seriously only as a sensible example of model-building, unlike the Mighty Hunter hypothesis which is useful only as an example of how not to construct a scientific theory." In a discussion covering several pages, they look at the features in question, such as the unique shape of the human nose, lack of bodily hair, the frowning muscles--not observed in other primates, but ascribed by Morgan to adaptation against glare on water--and the general appearance of the human body, that is, streamlined in the model of a cetacean or a pinniped, rather than bulky as other primates tend to be.
In the end, they admit "The other author, however, finds the aquatic evidence too strong to dismiss entirely," leaving the door open to open-minded consideration of new and existing evidence.
They agree, however, that Morgan and Hardy offer a list "longer and more persuasive than the equivalent list of the Mighty Hunter's advocates." Their biggest difficulty comes when trying to reconcile AAH's proposed timeline to what is known about hominid evolution, and the question of why, if an ape had spent so much time adapting to a watery environment, it bothered coming back to land at all.
In Morgan's view, this is explained by the geology around Hadar (Ethiopia), where an inland sea was created, but slowly became too saline to be hospitable, ejecting its newly-adapted inhabitants back onto dry land where they were able to put bipedalism and a larger brain to good use.
She also contends that tool use follows naturally if a primate, already perhaps adept at termite-fishing, found itself surrounded by thick-shelled meals and plentiful stones.
One thing leads to another rather smoothly if you accept the premise in the first place. In The Scars of Evolution, Morgan looks at some of the criticisms aimed at AAH as explained in her earlier works.
One of these is that primates and apes have an innate aversion to water, which would have prevented a voluntary shift toward the aquatic environment.
She deals with this by considering what was going on on the African continent at the time.
"...the apes stayed where they were and the sea came in to them, The vicinity of Hadar was one of the most unstable spots on the surface of the earth at the time of the ape/man split." (Morgan, The Scars of Evolution) She also postulates, based on the same terrestrial dynamics, a reasonable explanation for the original sea-to-land migration beginning 350 million years ago.
It's not that the fish wanted to leave the sea, but that the sea disappeared around them.
Such events are more the rule than the exception when one looks the planet's long-term continental fluctuations. She credits Leon P.
La Lumiere of the Naval Research Laboratory in Washington, D.C.
for piecing together the geological evidence.
"La Lumiere reasoned that if this aquatic interlude took place at all it must have had as its starting point a forested area inhabited by apes in the late Miocene.
He then postulated that speciation of the kind indicated by the fossil record strongly suggested that a population of the apes had become isolated over a prolonged period from others of their kind; and that any such isolation must have come to an end in the late Pliocene or early Pleistocene to account for the siting of early hominid fossils." (Morgan, The Aquatic Ape) La Lumiere studied the geological history of Africa and determined that the scenario Morgan describes was possible in Africa's Rift Valley.
"Populations of apes undoubtedly in those circumstances have found themselves isolated on Danakil, or on smaller islands, or marooned in the treetops of lower-lying forest areas invaded by the sea." (Morgan, The Aquatic Ape, quoting La Lumiere) La Lumiere is able to reconcile his geology with the molecular clock, and to provide a reasonable explanation for the return to land.
Although molecular dating could yield results more positive that stratigraphic or isotopic dating is capable of, it tends to leave rather large areas of wiggle room.
For instance: "Imagine that an ancestral species possessed a gene A.
Now imagine that a variant of the gene, A' , arose around 10 million years ago, making the gene polymorphic.
Individuals in the population of the common ancestor may now possess two copies of variant A (that is, homozygous for A), two copies of variant A' (homozygous for A'), or one copy of each variant (heterozygous), suppose that 5 million years ago the ancestral species split into three daughter species, X,Y, and Z.
In the population that leads to X, the variant A' is lost, leaving just A.
In the population that leads to Z, variant A is lost, leaving just A'.
A comparison of the sequences of this gene in species X and Z would indicate that they diverged 10 million years ago, despite the fact the speciation event occurred only 5 million years ago." (Lewin, Human Evolution) La Lumiere notes, in common with Darwin, that such islands are known to be areas of comparatively rapid evolutionary change.
It goes without saying that the Rift Valley is a rich source of fossil information from this critical period, something La Lumiere believes corroborates AAH, and could potentially provide conclusive evidence for it. Indeed, as Morgan points out, some sort of geological event isolating one or more groups of apes was a necessary condition for the kind of speciation that eventually led to Homo Habilis.
The idea also helps throw light on the mysterious inability of the robust and gracile australopithecines to adapt and survive along with later hominids, though their life history spans a considerable length of time. Probably the most serious attempt to actually debate AAH occurred in Valkenburg, The Netherlands, in 1987.
The European Sociobiological Society and the Dutch Association of Physical Anthropology convened a conference of 22 interested parties expressly to evaluate AAH. While no firm conclusion seems to have been reached, Valkenburg tended, tentatively, to refute AAH, according to the website www.riverapes.com.
The conference's epilogue was carefully worded, but pessimistic: "Our general conclusion is that, while there are a number of arguments favouring the AAT, they are not sufficiently convincing to counteract the arguments against it." At the same time, biological anthropologist Vernon Reynolds, in his summary, wrote, "...there does seem to be evidence that not only did they take to 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 of selection." The question of food resources is problematic in any savanna scenario, unless you're talking about a skilled hunter, which nobody seriously proposes for the era.
What you have is a determined scavenger, following the same herds exploited by some of the fiercest beasts ever to walk the earth.
It's hardly a situation that encourages continued and expanded commitment, especially when a much more reliable, and safer, food source is located nearby.
If we look at the baboon, who's lifestyle is most like that proposed for early hominids, we are struck by the lack of evolutionary progress as compared to the actual ape who got up on two legs and made a habit of it. Being scientists, the Valkenburg conferees were understandably cautious, as Hardy was, but they admitted "it may well be rewarding to reconsider the issue once further evidence--for instance from paleontology--becomes available." The subsequent discovery of Orrorin tugenensis could have a bearing on the question, but it has to be considered in that light for it to have much of an effect.
Valkenburg also noted that Hardy was not the first to put the pieces together as he did, although earlier writers seemed to escape notice.
Max Westenhoffer, at the University of Berlin, made a similar proposal in 1942, again trying to make sense of the features that so differentiate humans from the great apes.
G.L.
Sera discusses a similar idea in a 1924 paper, speculating that the platyrrhine monkeys became morphologically distinct from the catarrhines because of a period of aquatic development.
Perhaps Westenhoffer would have reached a wider audience were it not for Germany's total involvement in World War 2. In The Blind Watchmaker, Richard Dawkins uses the pebbles-on-the-beach analogy to eloquently show how what appears to be mere chance is actually an inevitable reaction to the machinery of physics.
The smaller pebbles on a beach are sorted from the larger ones through perfectly understandable hydrological action.
In the same way, we can look at what is known of primate evolution: from small beginnings larger animals radiated into niches as they became available and as competitive pressures or habitat loss made new strategies necessary.
There's nothing particularly mysterious about it.
To propose that an ape found a better and more reliable food source, and protection from landlubbing predators, by taking recourse to the shallow warm waters not far from their accustomed forests, is hardly an astonishing leap of imagination.
Modern maqaques enjoy resting in the hot springs when it snows and don't mind eating some crab from time to time. Nor was the aquatic ape the only primate ever to develop adaptations that can be interpreted as marine.
Although Oreopithecus is not considered to be in the human lineage, the evidence is plain that he lived in swampy forests (like Aegyptopithecus), and "It is characterized by the short iliac bones which are seen in most aquatic mammals, and in man and his ancestors." (Morgan, The Scars of Evolution).
As Peter Andrews and Chris Stringer conclude in Human Evolution, "Oreopithecus is an enigma over which scientists continue to argue, partly due to its strange morphology and partly to its potential importance to the general understanding of human evolution." They remark on the strong evidence of convergent evolution under circumstances not unlike those that confronted the common ancestor when she received her biological walking papers. The most amusing analysis of AAH comes from a psuedo-scientific website maintained by a religious "science" organization, (www.objectiveministries.org).
Of course the idea of an objective scientific ministry is humorous on its face, but for a real laugh, Dr.
Richard Paley informs believers that humans have what appear to be "semi-aquatic traits" (a grudging nod to the profound morphological riddle posed by human derived traits) so that "if one fell off the ship (Noah's Ark) he or she would be able to tread water until the others could help.
To this end He (God) created Adam and Eve with semi-aquatic features such as relative hairlessness and the ability to gulp air with their mouths as a pre-adaptation to the dilivuvian envirnoment." Paley's poor grasp of science is betrayed by his observation that AAH postulates an aquatic adaptive phase "billions" of years ago, the kind of statement that obviously weakens any further argument. But positive analysis of AAH can be found in such diverse publications as the U.K.'s Labor Left Bulletin.
Its credibility is probably not helped by positive attention from spacetransportation.org, but the idea is kept alive by such phenomena as the progressive rock band The Aquatic Ape.
Apparently the idea of aquatic hominids strikes a romantic chord in the human consciousness, another derived characteristic that has been used by Morgan's supporters, who seem to use emotion as much as intellect to back the argument. While none of this discussion leads to any final answers, we are able to conclude, in common with Ian Tattersal in The Fossil Trail that, "The setting in which human upright locomotion emerged seems poised for much future debate." In the end, that's all Hardy and Morgan ever asked for. Bibliography Andrews, P., Stringer, C., HUMAN EVOLUTION, Cambridge, Cambridge University Press, 1989 Dawkins, R., THE BLIND WATCHMAKER, New York, W.W.
Norton & co., 1996 Gibbons, J., Cherfas J., THE MONKEY PUZZLE, New York, Pantheon, 1982 Lewin, R., PRINCIPLES OF HUMAN EVOLUTION, Malden, MA and Oxford, Blackwell Science, 1993 Morgan, E., THE DESCENT OF WOMAN, New York, Stein and Day, 1972 Morgan, E., THE AQUATIC APE, New York, Stein and Day, 1982 Morgan, E., THE SCARS OF EVOLUTION, London, Oxford University Press, 1994 Tattersall, I., THE FOSSIL TRAIL, Oxford, Oxford Universtiy Press, 1995 Wolpoff, M.H., PALEOANTHROPOLOGY, Boston, McGraw Hill, 1999
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