Talk:Aquatic ape hypothesis

Hypothesis

Suggestion, see above (collapsed as it is very long)

Anthropological consensus on human evolution Family tree showing the extant hominoids: humans (genus Homo), chimpanzees and bonobos (genus Pan), gorillas (genus Gorilla), orangutans (genus Pongo), and gibbons (four genera of the family Hylobatidae: Hylobates, Hoolock, Nomascus, and Symphalangus). All except gibbons are hominids. Great Rift Valley in East Africa, key to human evolution. File:Paranthropus on Plains art.jpg A classic depiction of the consensus on the earliest evolution of hominins in East Africa, here Paranthropus. See also: Human evolution Modern humans, Homo sapiens, developed from earlier forms found as fossils at various locations around the world, seeing an early concentration in East Africa. Other remnants from early humans such as tools, foods, dwellings, etc., have also been detected. Combined, these finds present a partial image of the process, that developed the species Homo sapiens. From the collective work of anthropology, and in later years also genetics, established consensus states, that humans belong in the biological tribe Hominini, this in the family of Hominidae (the great apes), this in the order of primates, this in the class of mammals. Humans are closely related to, in order of closest kinship, the great ape generachimpanzees, gorillas, orangutans, and further distant the family of gibbons. Hominini includes the subtribe Australopithecina with the genera Sahelanthropus, Orrorin, Ardipithecus, Paranthropus, Australopithecines; and the subtribe Hominina, encompassing the genus Homo, some of its species being Homo habilis, Homo ergaster, Homo erectus, the Neanderthals and modern humans, the latter being the only extant species. There is still some uncertainty about the interrelation between the known Hominin fossils; new finds can still drastically rewrite the human family tree, most recently with Sahelanthropus. Contemporary anthropology estimates, that the direct ancestors of modern humans split from a common ancestor to chimpanzees somewhere between 4 and 8 million years ago in Africa; the fossil ape Sahelanthropus tchadensis which lived some 7 million years ago in Chad is considered the earliest possible homininin. Since the breakthrough of Darwin and Wallace's theory of evolution in the 19th century, it has been heavily debated why humans have features that distinguish them from their nearest evolutionary relatives; most notably by being near-furless, employing upright bipedal stance on their hind limbs, and having the perhaps most complex brain in the animal kingdom. A wide range of difficult to corroborate hypotheses have been presented as to the evolutionary background of the unique features of modern humans; for human bipedalism e.g. altered carrying behavior, improved energy efficiency, improved thermal regulation, altered social behavior and increased dominance behavior. The human split from the lineage of the chimpanzees is linked to the geological formation of the East African mountain range Great Rift Valley that extends from Djibouti to Mozambique. In this region are found many of the key fossils of the earliest hominins, leaving it to be considered the cradle of humanity. The most widely considered hypothesis is that woodland dwelling, brachiating hominoids, specifically on the eastern side of the mountain range, gradually lost their habitat to more open areas, for instance grasslands, and that this and other changes forced these hominoids to develop the shapes, that gradually resulted in modern humans. In recent decades, the traditional image of human origin having taken place in grasslands (e.g. the African savannah) has been challenged, since particularly the oldest homininin fossils are found alongside fossilized fauna and flora from traditional woodland habitats, rather than from grasslands, e.g. the some 4.4 million year old fossil Ardi, an Ardipithecus ramidus. The basis of AAH AAH argues, that many features that distinguish humans from their nearest evolutionary relatives emerged because the ancestors of humans underwent a period adapting to a semiaquatic existence, arguing convergent evolution with other aquatic and semiaquatic, chiefly mammal, species. It is traditionally argued, that semiaquatic hominins later returned to a more terrestrial life before becoming fully aquatic, as e.g. whales and dolphins. Variations amongst AAH proponents suggest these proto-humans to have spent time either wading, swimming or diving on the shores of fresh, brackish, alcalic or saline waters, or different such habitats at different time frames, while feeding on littoral resources. Key arguments have been developed and presented by Elaine Morgan since 1972, these based on the original suggestion of Alister Hardy. In later years, other contributors have further developed the aquatic ideas, some of which differ heavily from the original "aquatic ape" of Hardy et Morgan. The term waterside hypotheses of human evolution has been coined by AAH-proponent Algis Kuliukas to collectively represent this diversity, of which AAH is only one such hypothesis. Most traits perceived as aquatic are physiological and biochemical, while few are behavioral (ethological). The time frame for the origin og possible termination of such an aquatic existence also differs between proponents, or though the same time frame as anthropological consensus is generally followed. In most cases, this aquaticism is perceived as having been instigated by selective pressure around the split of the last common ancestor between humans and chimpanzees. The Belgian physician Marc Verhaegen has presented a unique variation of AAH, where semiaquatic traits is argued to be evident even before the split between humans and chimpanzees, this in Dryopithecus-like apes between 15 to 7 million years ago, which at that time had migrated from rain forests in Africa to then tropical rainforests around the Tethys Sea, the Mediterranean and across Southern Asia. At the end of this warmer period, the ancestors of orangutans is said to have migrated into South East Asia, while the ancestors of humans, chimps and gorillas migrated back into Africa, evolving into their present forms; chimps and gorillas becoming more land locked, while humans developed aquatic traits. Verhaegen also argues, that human aquaticism reached its peak with Homo erectus some 2-1 million years ago, this observed by e.g. thickened erectus bones, labeled pachyosteosclerosis, which is argued as having convergence during e.g. whale evolution from land to aquatic forms. Verhaegen further argues, that human aquaticism originally developed in tropical mangrove or seasonally flooded woodland, this based on the flora and fauna found alongside the earliest hominin fossils, a phenomenon he labels aquarborealism. The argued degree of human aquaticism varies amongst proponents, however the vast majority argues a semiaquatic ape on par with e.g. hippos and sea otters. Very few have argued a fully aquatic stage on par with e.g. whales or pinnipeds, and this is rejected by the majority, including Morgan. Some pseudoscientific and cryptozoologic speculations have made use of parts of the AAH argumentation, e.g. the claimed existence of mermaids, but this is also rejected by proponents, including Morgan. While most proto-human fossil sites are associated with wet conditions upon the death of the hominins, this is not seen as unequivocal evidence for the AAH, since being buried in waterside sediment is one of the rare situations in which fossilization is likely to occur (labeled preservation bias); paleontologists are aware of this preservation bias and expect fossils to be located at such sediments. Physiological and biochemical claims Bipedalism is argued as an adaptation to wading in shallow waters. Bipedalism: The habitual, upright bipedalism of extant humans is argued as an adaptation to wading along shallow coastlines. Proponents of AAH argues, that bipedalism offers numerous advantages in water, including permitting deeper wading, improved balance, reduced strain on the back, hips and knees as well as improved blood circulation. Proponents point towards a similar upright bipedal stride employed by a wide range of ape and monkey species, when wading in shallow waters, e.g. chimps, gorillas, orangutans, baboons, macaques, etc. Fossilized remains indicate, that as early as Toumaï (a Sahelanthropus tchadensis), living 7 million years ago alongside Lake Megachad, human ancestors were bipedal. Proponents of AAH suggest that bipedalism is disadvantageous when comparing humans to medium-sized, terrestrial quadrupeds, and the fossil record shows that the evolution of humans from ape ancestors didn't include a period of quadrupedal locomotion. Instead, human transitional evolution features mainly brachiation, suspension and climbing as the primary method of transportation, with a gradual increase in bipedal locomotion over time. Critics argue, that bipedialism also provides many advantages on land, particularly lower energy expenditure and the ability of long-distance running, which humans is suggested as being better at than most terrestrial mammals. In addition, the elongated lower limbs of humans, which is explained by AAH proponents as improving swimming speeds, appears only after the evolution of the genus Homo and biomechanical analysis argues, that humans are poor swimmers, and that pre-human apes would face similar problems. There is no single accepted explanation for human bipedalism, other suggested models are freeing the hands for tool use, carrying of infants, feeding adaptations, improved energy expenditure or some combination of these, with considerable diversity in pre-human skeletal adaptations that would assist in bipedalism. Loss of fur in humans is argued to be convergent with aquatic and semiaquatic mammals. The insulating layer of fat in the human skin (shown here as yellow beads) is perceived as a primitive layer of blubber. Hairlessness and subcutaneous fat: Morgan claims that the near-hairless skin of humans, unique among all simians and the majority of mammals, is comparable to adaptations in aquatic mammals, apart from whales, pinnipeds and sirenia also semiaquatic hippos, and land-dwelling mammals with aquatic ancestors, such as elephants and rhinos. Morgan has furthered Hardy's original observation, that what body hair humans do have follows the flow of water over the body. Morgan also argues, that the human insulating layer of fat beneath the dermis is not present in the other great apes, and can be perceived as a primitive form of blubber. Critics argue, that humans vary strongly in the amount and distribution of body hair and that comparably sized mammals adapted to semiaquatic lifestyles just as often as not have dense, insulating fur, e.g. otters, or large, barrel-shaped bodies that retain heat well in water, e.g. hippos. Though a variety of explanations have been proposed for human hairlessness, the best-supported theory involves improved cooling through perspiration; while fur helps cool inactive animals, hairless skin that sweats vigorously is argued as being much better at cooling humans who generate body heat through activity. Langdon, in his 1997 critique of AAH, stated that the streamlining features attributed to hair follicle distribution and direction would be more reasonably achieved through changes in the shape of the skeleton and soft tissues. The inherent human diving ability far exceeds all other simians. Descended larynx, breath control and speech: The human larynx is situated in the throat rather than the nasal cavity, a feature shared by some aquatic animals who use it to close off the trachea while diving and facilitates taking large breaths of air upon surfacing. Humans also have a considerable amount of control over their breathing, which is an involuntary reflex for most terrestrial mammals. In humans, the descended larynx and increased breath control allows for habitual verbalism, such as complex speech, music, etc. In a controversial claim, Morgan suggests that the use of speech has possible precendents in other aquatic mammals, most notably whales and seals. Humans possess a strong diving reflex, allowing them, with exposure, to hold its breath for minutes at a time and dive long distances under water as well as to great depths, as much as to 50 meters depth unassisted by diving equipment, etc. This makes humans by far the best diver among all simians, seeing a rare parallel in the semiaquatic proboscis monkey from Indonesia, having been observed diving untill 20 meters. After brief water exposure of the body, the humans spleen contracts to spew a reserve of red blood cells into the cardiovascular system, allowing for longer breathholds, which Morgan argues has precedents in e.g. pinnipeds. Counter to these arguments, it has been pointed out, that a terrestrial mammal such as the red deer also have a permanently descended larynx, allowing it for extended verbalism, or though without conscious breath control. Breath control has also been argued as having been preceded by bipedalism, which frees up the muscles of the upper torso from locomotion and allows breathing independent of limb position. Both of these adaptations are thought to derive from improvements in vocalization and the evolution of the ability to speak. and the human larynx is shaped differently from that of aquatic animals, predisposing humans to choking. Shellfish is argued as a possible prehistoric source to the expansion of the human brain. Encephalization: The human encephalization quotient, an expression of the size and complexity of the brain of a species, compared to its physical size and other factors, is considered the highest in the animal kingdom, followed by whales, in particular dolphins, other great apes, elephants, certain spiecies of squid and some intelligent birds. It has been argued, that aquatic mammals more often develop large brains, and that particularly grassland mammals conversely stagnate in brain development. Morgan and other authors have suggested that the encephalization of the human brain was a response to increased consumption of seafood. A team lead by Canadian biochemist Stephen Cunnane has argued, that both developing and maintaining a healthy human brain is heavily dependent on a key series of micronutrients, most especially DHA (an Omega 3 fatty acid) and iodine-ions. Both these have proven extremely rare in purely terrestrial food groups (including cereals, fruits, vegetables and husbandry meats), but are conversely abundant in fish, shellfish and other sea foods, particular from saline and alcalic waters. Critics have argued, that considerable human encephalization began quite late in the development of the genus Homo, particularly with Homo erectus, long after the development of bipedalism. Bipedalism had occurred already in the australopithecines (4.2–3.9 mya) and Ardipithecus (4.4 mya), and perhaps as early as in the species Sahelanthropus tchadensis (approx. 7 mya). On the other hand increase in cranial capacity occurs quite late in the fossil record: Homo habilis (approx. 2 mya) for example, while fully bipedal, had a brain size within the range of modern day gorillas. Counter to this, Cunnane et al have argued, that a transition of semiaquatic Hominina-forms from fresh water habitats in the hinterland of Africa to more alcalic and saline habitats in Eastern Africa, e.g. in the then sea-flooded Afar-triangle in modern Ethiopia, could have supported the increase in human brain size through an increased access to e.g. DHA and iodine rich foods. It is argued, that molluscs, e.g. clams and oysters, as found along the shores of East Africa and in alcalic lakes along the Great Rift Valley has an optimal composition to support the extant human brain's nutritional needs. Proponents point to archaeological finds of shellfish kitchen middens as far back as in middle pleistocene some 164,000 years ago, during the earliest days of archaic Homo sapiens. Conversely, critics argue that landlocked humans without access to seafood develop normal brains and that these nutritional requirements can be met with a sepcific terrestrial diet. The encephalization of early Homo species is also argued as having been possibly driven by the consumption of hunted or scavenged animal brains supplying large amounts of scarce nutrients including docosahexaenoic acid. Reproduction: Morgan and others point to the increased adiposity of human infants, a marked difference from the offspring of other great apes. THis is suggested as an adaptation to increased insulation and buoyancy in water for human babies. It is pointed out, that vernix caseosa, a cheesy varnish coating the skin of newborn babies, apart from humans so far has only been observed on the cups of a few pinniped species, harbour seals. It is pointed out, that infant humans cannot walk upright, untill as much as one year of age, completely unknown among simian offspring, e.g. grassland-dwelling baboons. Morgan also claims, that newborns are adequately suited to swim along with their mother, while being able to hold their breath upwards of 45 seconds. Historically, women throughout the world have experienced a series of potentially life-threatening circumstances delivering above water, while Morgan and others, e.g. the French physician Michel Odent, point to recent decades of studies into baby swimming and water birth, which is argued to relieve stress and pain effects for both mother and child, with no corresponding observed drowning risks for the child. Morgan also points to unique features of both men and women's genitals, and the woman's protruding, fat-filled bosom as possible aquatic adaptations, with alleged convergence observed in sirenia. Presented criticism to these claims include the infant's increased risk of drowning if parting from its mother, coupled with observations of both young children as well as adults developing aquaphobia, while baby swimming and water birth are being rejected as fads. Ethological claims Habitat: Proponents of AAH argue, that the concentration of the contemporary world population of more than 7 billion people illustrates a trend for Homo sapiens to cling together in coastal regions alongside river valleys, lakes and seashores, in modern times particularly in India and China. Critics argue that this cannot disclose a similar trend in the eon long development of Homo, as modern human urbanization is said to be dependent on easier transit routes, this including rivers and seas. Conversely, Morgan argues, that humans have a similar preference for recreation sites along said coastal regions, e.g. tropical beaches. The bathing abe. Bathing behavior: Across the globe, humans employ hygiene bathing, this regardless of faction, ethnicity, gender, etc. This is argued as a behavioral relic of a semiaquatic stage. As an offshoot to the argument that other traditional terrestrial mammal groups may also be past semiaquatics, similar behavioral traits in both African and Asian elephants, which are also observed bathing regularly with its whole body submerged. Other claims Rare presented AAH-arguments points to the human tendency to watery psychic tears, and also sweat to cool down, where Morgan has withdrawn previous arguments, seeing that horses is a rare mammal species to also sweat profusely. It is occasionally argued, that humans compared to other apes have reduced olfaction, with claimed convergences observed in other aquatics, e.g. whales; that the protuding human nose would be adapted to keep splashes out of nasal cavities, arguing the semiaquatic proboscis monkey or semiaquatic tapirs as possible convergences; the tendency of partial to full baldness in men; the tendency for human obesity; and that human kidneys are better suited for excretion of salt than other apes. Such arguments are generally considered more speculative and is often heavily critized. Theoretical considerations Critics of AAH note, that the descended larynx is not exclusive to humans in terrestrials, but also found in red deers. Elaine Morgan has retracted an early AAH-argument of human sweating being an aquatic indicator after critics cited, that also horses sweat. The AAH has been criticized for containing multiple inconsistencies and lacking evidence from the fossil record to support its claims (Morgan, for instance, failed to discuss any fossils found after 1960 and much of her analysis is by comparing soft tissues between humans and aquatic species). It is also described as lacking parsimony, despite purporting to be a simple theory uniting many of the unique anatomical features of humans. Anthropologist John D. Hawks expresses the view that rather than explaining human traits simply and parsimoniously, it actually requires two explanations for each trait - first that proximity to water drove human evolution enough to significantly change the human phenotype and second that there was significant evolutionary pressure beyond mere phylogenetic inertia to maintain these traits (which would not be adaptive on dry land) and points out that exaptation is not an adequate reply. Hawks concludes by saying: In other words, the Aquatic Ape Theory explains all of these features, but it explains them all twice. Every one of the features encompassed by the theory still requires a reason for it to be maintained after hominids left the aquatic environment. Every one of these reasons probably would be sufficient to explain the evolution of the traits in the absence of the aquatic environment. This is more than unparsimonious. It leaves the Aquatic Ape Theory explaining nothing whatsoever about the evolution of the hominids. This is why professional anthropologists reject the theory, even if they haven't fully thought through the logic. Ellen White describes Morgan's work as failing to be empirical, not addressing evidence that contradicts the theory, relying on comparative anatomy rather than selection pressure, not predicting any new evidence and failing to address its own shortcomings. White stated that while the theory had the scientific characteristics of explanatory power and public debate, the only reason it has received any actual scholarly attention is due to its public appeal, ultimately concluding the AAH was unscientific. Others have similarly noted the AAH "is more an exercise in comparative anatomy than a theory supported by data." Though describing the hypothesis as plausible, Henry Gee went on to criticize it for being untestable, as most of the evolutionary adaptations described by Morgan would not have fossilized. Gee also stated that, while purely aquatic mammals such as whales show strong skeletal evidence of adaptation to water, humans and human fossils lack such adaptations (a comment made by others as well); that there are many hypothetical and equally plausible scenarios explaining the unique characteristics of human adaptation without involving an aquatic phase of evolution; and that proponents are basing arguments about past adaptations on present physiology, when humans are not significantly aquatic. There is ultimately only circumstantial evidence to suggest, and no solid evidence to support the AAH. ScienceBlogs author Greg Laden has described the AAH as a "human evolution theory of everything" that attempts to explain all anatomical and physiological features of humans and is correct in some areas only by chance. Laden also states that the AAH was proposed when knowledge of human evolutionary history was unclear, while more recent research has found that many human traits have emerged at different times over millions of years, rather than simultaneously due to a single evolutionary pressure. Evolutionary biologist Carsten Niemitz states that he believes the AAH as expressed by Morgan didn't fulfill the criteria of a theory or a hypothesis, merely "[listing] analogies of features of savannah type mammals on the one hand and of aquatic mammals and man on the other, asking the scientific community for explanations other than a common aquatic ancestor of extant man." Marc Verhaegen has also challenged the AAH as expressed by Morgan, believing the ancestors of apes as well as humans may have had their evolutionary history influenced by exposure to flooded forest environments, and that based on the hominin fossil record, regular part-time underwater foraging began in the Pleistocene rather than the early Pliocene as Morgan’s model proposes. In 2012 Langdon reviewed an e-book published by Bentham Science Publishers collecting 50 years of theorizing about the AAH. In his review, Langdon noted the lack of a single "aquatic ape hypothesis", instead there are multiple hypotheses with a common theme of evolutionary pressure due to dependence on an aquatic habitat. While original versions thought to explain an apparently substantial gap between humans and closely related common ancestors, more recent variants of these hypotheses have had to adjust to the fact that the gap was more apparent than real and the significant commonalities found between humans and other African apes. Three main strands of thought now exist regarding the AAH, varying according to when the theorized aquatic phase occurred - from the Middle Miocene to approximately three million years ago (Hardy's original model, which was based on a large gap in the fossil record that has since been filled in), from the Early Miocene when ancestral hominids were thought to wade in costal swamps and from which Homo species were thought to split off and adapt to swimming and diving (associated with the work of Marc Verhaegen), and from 200,000 years ago when exploitation of costal resources led humans out of Africa and resulted in the evolution of modern humans (associated with the work of Algis Kuliukas). Langdon notes the strong associations of humans with water, as well as the adaptability of the species to incredibly diverse ecological niches (including costal and wetland regions), both within and across lifetimes. Whether these associations define humans as "semiaquatic" or not "represents a fundamental point of departure between anthropologists and the [Aquatic Hypothesis] community." Langdon notes the three lines of evidence cited to support the AAH (comparative anatomy between humans and other semiaquatic species; hypothetical situations in which evolutionary pressure might have produced convergent evolution between humans and semiaquatic species; the ability for humans to perform various activities in the water) and concludes about these lines of evidence, These rhetorical strategies create long lists of claims, but until each hypothesis is independently established, it does not constitute evidence for an aquatic scenario. At best it shows consistency with a prior assumption. Evolutionary convergence – structural similarity – by itself is a metaphor for functional similarity. Metaphors are useful, but they demand that we examine points of resemblance closely in order to learn whether they are meaningful. Like metaphors, evolutionary convergences have their limits: eventually differences will emerge. Dolphins and humans are similar in the loss of body hair, relatively large brains, and complex vocal capacities; but these similarities do not make us dolphins. Nor is it clear which, if any of these similarities are related to water. Each trait must be investigated and resolved as a separate functional and evolutionary question. Unproven suppositions cannot serve as evidence for other hypotheses. Langdon criticizes the alleged "parsimony" of the AAH irrelevant as it is used to generate hypotheses about human adaptation – but does not prove them. The AAH is, like many Just So Stories in anthropology, ignored less because of prejudice than because of a lack of empirical evidence to support it, because it engages only with supporting evidence in the relevant scientific literature while ignoring the larger body of unsupporting evidence, and because its hypotheses are portrayed as "compatible with" more accepted hypotheses and thus unable to distinguish between or provide explicit evidence for the AAH. Langdon concludes his review: It is now incumbent upon both authors and critics to clarify the assumptions with which they are working and, where possible, to make empirically testable predictions. Similarly, the many gloating references in this book to the collapse of the Savannah Hypothesis should not suggest that all terrestrial models have been challenged. Possibly the time has come to bring the “paradigms” together; to step out of the “us vs. them” mentality held by both sides of this debate; and simply to recognize that dozens of speculative hypotheses for human evolution exist in the literature that may or may not discuss a relationship with water. The authors of the volume published a reply. ... End of new "Hypothesis" section draft ...

New version - again!

Let's have a little fun with the denier. Please explain again just how the below version is POV-pushing?

Suggested revision

Newborns float and hold their breath instinctively when submerged. This is argued to be one of many aquatic adaptations by proponents of the aquatic ape hypothesis. A female gorilla wades across a body of water. Observed bipedalism in many simian species in shallow water is argued as illustrative of the origin of human bipedalism. The aquatic ape hypothesis (AAH) or aquatic ape theory (AAT) is a hypothesis about human evolution which posits that the ancestors of modern humans spent a period of time adapting to a semiaquatic existence. AAH emerged from the observation that some anatomical and physiological traits that set humans apart from other primates have parallels in aquatic mammals. The hypothesis was first proposed by German pathologist Max Westenhöfer in 1942, and then independently by English marine biologist Alister Hardy in 1960. After Hardy, the most prominent proponent was Welsh writer Elaine Morgan, who has written several books on the topic. AAH is not accepted among the mainstream explanations of human evolution. Scientific consensus states that humans first evolved during a period of rapid climate fluctuation between wet and dry, and that most of the adaptations that distinguish humans from the great apes are adaptations to a terrestrial, as opposed to an earlier, arboreal environment. Few paleoanthropologists have explicitly evaluated AAH in scientific journals, and those that have reviewed the hypothesis have been critical. An extensive criticism appeared in a peer reviewed paper by John H. Langdon in 1997. Langdon states that the AAH is one of many hypotheses attempting to explain human evolution through a single causal mechanism, and that the evolutionary fossil record does not support such a proposal; that the hypothesis is internally inconsistent, has less explanatory power than its proponents claim, and that alternative terrestrial hypotheses are much better supported. AAH is popular among laypeople and has continued support by a minority of scholars. Langdon attributes this to the attraction of simplistic single-cause theories over the much more complex, but better supported models with multiple causality. History The German pathologist Max Westenhöfer (1871–1957) can be said to have worded an early version of AAH, which he labeled "the aquatile man" (German: Aquatile Mensch), which he described in several publications during the 1930s and 1940's. Westenhöfer was partially influenced by contemporary German National Socialism and disputed Charles Darwin's theory on the kinship between modern man and the great apes. As part of a complex and unique presentation of human evolution, he argued that a number of traits in modern humans derived from a fully aquatic existence in the open seas, and that humans only in recent times returned to land. In 1942, he stated: "The postulation of an aquatic mode of life during an early stage of human evolution is a tenable hypothesis, for which further inquiry may produce additional supporting evidence." Westenhöfer’s aquatic thesis suffered from a number of inconsistencies and contradictions, and consequently he abandoned the concept in his writings on human evolution around the end of the Second World War. Independently and ignorant of Westenhöfer's writings, marine biologist Alister Hardy (1896-1985) had since 1930 also hypothesized, that humans may have had ancestors more aquatic than previously imagined, although his work conversely was rooted in the Darwin consensus. As a young academic with a hypothesis belonging to a topic outside his field, and because he was aware of its inherent controversy, Hardy delayed reporting his idea for some thirty years. After he had become a respected academic and knighted for contributions to marine biology, Hardy finally voiced his thoughts in a speech to the British Sub-Aqua Club in Brighton on 5 March 1960. Several national newspapers reported distorted versions of Hardy's ideas, which he countered by explaining them more fully in an article in New Scientist on 17 March 1960. Hardy defined his idea: My thesis is that a branch of this primitive ape-stock {hominoids} was forced by competition from life in the trees to feed on the sea-shores and to hunt for food, shell fish, sea-urchins etc., in the shallow waters off 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. The idea received some interest after the article was published, but was generally ignored by the scientific community thereafter. In 1967, the hypothesis was briefly mentioned in The Naked Ape, a book by Desmond Morris (1928–) in which can be found the first use of the term "aquatic ape". While doing research for her book "The Descent of Woman" published in 1972, a book inspired by reading Morris' The Naked Ape, TV-writer Elaine Morgan (1920-2013) was struck by the potential explanatory power of Hardy's hypothesis. While elaborating on Hardy's suggestion, Morgan also sought to challenge what she considered a masculine domination of the debate on human evolution, and the satirical book became an international bestseller, making Morgan a popular figure in feminist movements and on various TV talkshows in, for example, the United States. Conversely, her scientific contributions, including her elaboration on Hardy's aquatic humans was effectively ignored by anthropology. Morgan has since been the force majeure behind the development of Hardy's original idea, which after a number of publications culminated in 1997 with the book "The Aquatic Ape Hypothesis", which, with its now more factual language and proper referencing, was aimed primarily at the academic community. In 1987 a symposium was held in Valkenburg, the Netherlands, to debate the pros and cons of AAH. The proceedings of the symposium were published in 1991 with the title "Aquatic Ape: Fact or fiction?". The chief editor summarized the results of the symposium as failing to support the idea that human ancestors were aquatic, but there is also some evidence that they may have swum and fed in inland lakes and rivers, with the result that modern humans can enjoy brief periods of time spent in the water. Weaker versions of the hypothesis suggesting littoral feeding and wading rather than strong aquatic adaptation have since been proposed. These weaker versions of the hypothesis have not yet been scientifically explored. The context of the initial presentations of AAH (a popular essay and a political text) diverted attention away from the possible scientific merits of the hypothesis. Most paleoanthropologists reject the AAH; but it has never been seriously scrutinized and discussed within the field of paleoanthropology. Hypothesis Anthropological consensus on human evolution Family tree showing the extant hominoids: humans (genus Homo), chimpanzees and bonobos (genus Pan), gorillas (genus Gorilla), orangutans (genus Pongo), and gibbons (four genera of the family Hylobatidae: Hylobates, Hoolock, Nomascus, and Symphalangus). Great Rift Valley in East Africa, key to human evolution. File:Paranthropus on Plains art.jpg A classic depiction of the consensus on the earliest evolution of hominins in East Africa, here Paranthropus. See also: Human evolution Modern humans, Homo sapiens, developed from earlier forms found as fossils at various locations around the world, seeing an early concentration in East Africa. Other remnants from early humans such as tools, foods, dwellings, etc., have also been detected. Combined, these finds present a partial image of the process, that developed the species Homo sapiens. From the collective work of anthropology, and in later years also genetics, established consensus states, that humans belong in the biological tribe Hominini, this in the family of Hominidae (the great apes), this in the order of primates, this in the class of mammals. Humans are closely related to, in order of closest kinship, the great ape genera chimpanzees, gorillas, orangutans, and further distant the family of gibbons. Hominini includes the subtribe Australopithecina with the genera Sahelanthropus, Orrorin, Ardipithecus, Paranthropus, Australopithecines; and the subtribe Hominina, encompassing the genus Homo, some of its species being Homo habilis, Homo ergaster, Homo erectus, the Neanderthals and modern humans, the latter being the only extant species. There is still some uncertainty about the interrelation between the known Hominin fossils; new finds can still drastically rewrite the human family tree, most recently with Sahelanthropus. Contemporary anthropology estimates, that the direct ancestors of modern humans split from a common ancestor to chimpanzees somewhere between 4 and 8 million years ago in Africa; the fossil ape Sahelanthropus tchadensis which lived some 7 million years ago in Chad is considered the earliest possible homininin. Since the breakthrough of Darwin and Wallace's theory of evolution in the 19th century, it has been heavily debated why humans have features that distinguish them from their nearest evolutionary relatives; most notably by being near-furless, employing upright bipedal stance on their hind limbs, and having the perhaps most complex brain in the animal kingdom. A wide range of difficult to corroborate hypotheses have been presented as to the evolutionary background of the unique features of modern humans; for human bipedalism e.g. altered carrying behavior, improved energy efficiency, improved thermal regulation, altered social behavior and increased dominance behavior. The human split from the lineage of the chimpanzees is linked to the geological formation of the East African mountain range Great Rift Valley that extends from Djibouti to Mozambique. In this region are found many of the key fossils of the earliest hominins, leaving it to be considered the cradle of humanity. The most widely considered hypothesis is that woodland dwelling, brachiating hominoids, specifically on the eastern side of the mountain range, gradually lost their habitat to more open areas, for instance grasslands, and that this and other changes forced these hominoids to develop the shapes, that gradually resulted in modern humans. In recent decades, the traditional image of human origin having taken place in grasslands (e.g. the African savannah) has been challenged, since particularly the oldest homininin fossils are found alongside fossilized fauna and flora from traditional woodland habitats, rather than from grasslands, e.g. the some 4.4 million year old fossil Ardi, an Ardipithecus ramidus. The basis of AAH AAH suggests that many features that distinguish humans from their nearest evolutionary relatives emerged because the ancestors of humans underwent a period when they were adapting to an aquatic or semi-aquatic way of life, but returned to terrestrial life before having become fully adapted to the aquatic environment. Variations within the hypothesis suggests these protohumans to have spent time either wading, swimming or diving on the shores of fresh, brackish or saline waters and feeding on littoral resources. Key arguments have been developed and presented by Elaine Morgan since 1972, these based on the original suggestion of Alister Hardy. In later years, other contributors have further developed the aquatic ideas, some of which differ heavily from the original "aquatic ape" of Hardy et Morgan. The term waterside hypotheses of human evolution has been coined by AAH-proponent Algis Kuliukas to collectively represent this diversity, of which AAH is only one such hypothesis. Most traits perceived as aquatic are physiological and biochemical, while few are behavioral (ethological). The time frame for the origin og possible termination of such an aquatic existence also differs between proponents, or though the same time frame as anthropological consensus is generally followed. In most cases, this aquaticism is perceived as having been instigated by selective pressure around the split of the last common ancestor between humans and chimpanzees. The Belgian physician Marc Verhaegen has presented a unique variation of AAH, where semiaquatic traits is argued to be evident even before the split between humans and chimpanzees, this in Dryopithecus-like apes between 15 to 7 million years ago, which at that time had migrated from rain forests in Africa to then tropical rainforests around the Tethys Sea, the Mediterranean and across Southern Asia. At the end of this warmer period, the ancestors of orangutans is said to have migrated into South East Asia, while the ancestors of humans, chimps and gorillas migrated back into Africa, evolving into their present forms; chimps and gorillas becoming more land locked, while humans developed aquatic traits. Verhaegen also argues, that human aquaticism reached its peak with Homo erectus some 2-1 million years ago, this observed by e.g. thickened erectus bones, labeled pachyosteosclerosis, which is argued as having convergence during e.g. whale evolution from land to aquatic forms. Verhaegen further argues, that human aquaticism originally developed in tropical mangrove or seasonally flooded woodland, this based on the flora and fauna found alongside the earliest hominin fossils, a phenomenon he labels aquarborealism. The argued degree of human aquaticism varies amongst proponents, however the vast majority argues a semiaquatic ape on par with e.g. hippos and sea otters. Very few have argued a fully aquatic stage on par with e.g. whales or pinnipeds, and this is rejected by the majority, including Morgan. Some pseudoscientific and cryptozoologic speculations have made use of parts of the AAH argumentation, e.g. the claimed existence of mermaids, but this is also rejected by proponents, including Morgan. While most proto-human fossil sites are associated with wet conditions upon the death of the hominins, this is not seen as unequivocal evidence for the AAH, since being buried in waterside sediment is one of the rare situations in which fossilization is likely to occur (labeled preservation bias); paleontologists are aware of this preservation bias and expect fossils to be located at such sediments. Physiological and biochemical claims Bipedalism is argued as an adaptation to wading in shallow waters. Bipedalism: The habitual, upright bipedalism of extant humans is argued as an adaptation to wading along shallow coastlines. Proponents of AAH argues, that bipedalism offers numerous advantages in water, including permitting deeper wading, improved balance, reduced strain on the back, hips and knees as well as improved blood circulation. Proponents point towards a similar upright bipedal stride employed by a wide range of ape and monkey species, when wading in shallow waters, e.g. chimps, gorillas, orangutans, baboons, macaques, etc. Fossilized remains indicate, that as early as Toumaï (a Sahelanthropus tchadensis), living 7 million years ago alongside Lake Megachad, human ancestors were bipedal. Proponents of AAH suggest that bipedalism is disadvantageous when comparing humans to medium-sized, terrestrial quadrupeds, and the fossil record shows that the evolution of humans from ape ancestors didn't include a period of quadrupedal locomotion. Instead, human transitional evolution features mainly brachiation, suspension and climbing as the primary method of transportation, with a gradual increase in bipedal locomotion over time. Critics argue, that bipedialism also provides many advantages on land, particularly lower energy expenditure and the ability of long-distance running, which humans is suggested as being better at than most terrestrial mammals. In addition, the elongated lower limbs of humans, which is explained by AAH proponents as improving swimming speeds, appears only after the evolution of the genus Homo and biomechanical analysis argues, that humans are poor swimmers, and that pre-human apes would face similar problems. There is no single accepted explanation for human bipedalism, other suggested models are freeing the hands for tool use, carrying of infants, feeding adaptations, improved energy expenditure or some combination of these, with considerable diversity in pre-human skeletal adaptations that would assist in bipedalism. Loss of fur in humans is argued to be convergent with some furless aquatic, semiaquatic and former semiaquatic (e.g. elephants) mammals. The insulating layer of fat in the human skin (shown here as yellow beads) is perceived as a primitive layer of blubber. Hairlessness and subcutaneous fat: Morgan claims that the near-hairless skin of humans, unique among all simians and the majority of mammals, is comparable to adaptations in aquatic mammals, apart from whales, pinnipeds and sirenia also semiaquatic hippos, and land-dwelling mammals with aquatic ancestors, such as elephants and rhinos. Morgan has furthered Hardy's original observation, that what body hair humans do have follows the flow of water over the body. Morgan also argues, that the human insulating layer of fat beneath the dermis is not present in the other great apes, and can be perceived as a primitive form of blubber. Critics argue, that humans vary strongly in the amount and distribution of body hair and that comparably sized mammals adapted to semiaquatic lifestyles just as often as not have dense, insulating fur, e.g. otters, or large, barrel-shaped bodies that retain heat well in water, e.g. hippos. Though a variety of explanations have been proposed for human hairlessness, the best-supported hypothesis involves improved cooling through perspiration; while fur helps cool inactive animals, hairless skin that sweats vigorously is argued as being much better at cooling humans who generate body heat through activity. Langdon, in his 1997 critique of the hypothesis, stated that the streamlining features attributed to hair follicle distribution and direction would be more reasonably achieved through changes in the shape of the skeleton and soft tissues. The inherent human diving ability far exceeds all other simians. Descended larynx, breath control and speech: The human larynx is situated in the throat rather than the nasal cavity, a feature shared by some aquatic animals who use it to close off the trachea while diving and facilitates taking large breaths of air upon surfacing. Humans also have a considerable amount of control over their breathing, which is an involuntary reflex for most terrestrial mammals. In humans, the descended larynx and increased breath control allows for habitual verbalism, such as complex speech, music, etc. In a controversial claim, Morgan suggests that the use of speech has possible precendents in other aquatic mammals, most notably whales and seals. Humans possess a strong diving reflex, allowing them, with exposure, to hold its breath for minutes at a time and dive long distances under water as well as to great depths, as much as to 50 meters depth unassisted by diving equipment, etc. This makes humans by far the best diver among all simians, seeing a rare parallel in the semiaquatic proboscis monkey from Indonesia, having been observed diving untill 20 meters. After brief water exposure of the body, the humans spleen contracts to spew a reserve of red blood cells into the cardiovascular system, allowing for longer breathholds, which Morgan argues has precedents in e.g. pinnipeds. Counter to these arguments, it has been pointed out, that a terrestrial mammal such as the red deer also have a permanently descended larynx, allowing it for extended verbalism, or though without conscious breath control. Breath control has also been argued as having been preceded by bipedalism, which frees up the muscles of the upper torso from locomotion and allows breathing independent of limb position. Both of these adaptations are thought to derive from improvements in vocalization and the evolution of the ability to speak. and the human larynx is shaped differently from that of aquatic animals, predisposing humans to choking. Shellfish is argued as a possible prehistoric source to the expansion of the human brain. Encephalization: The human encephalization quotient, an expression of the size and complexity of the brain of a species, compared to its physical size and other factors, is considered the highest in the animal kingdom, followed by whales, in particular dolphins, other great apes, elephants, certain spiecies of squid and some intelligent birds. It has been argued, that aquatic mammals more often develop large brains, and that particularly grassland mammals conversely stagnate in brain development. Morgan and other authors have suggested that the encephalization of the human brain was a response to increased consumption of seafood. A team lead by Canadian biochemist Stephen Cunnane has argued, that both developing and maintaining a healthy human brain is heavily dependent on a key series of micronutrients, most especially DHA (an Omega 3 fatty acid) and iodine-ions. Both these have proven extremely rare in purely terrestrial food groups (including cereals, fruits, vegetables and husbandry meats), but are conversely abundant in fish, shellfish and other sea foods, particular from saline and alcalic waters. Critics have argued, that considerable human encephalization began quite late in the development of the genus Homo, particularly with Homo erectus, long after the development of bipedalism. Bipedalism had occurred already in the australopithecines (4.2–3.9 mya) and Ardipithecus (4.4 mya), and perhaps as early as in the species Sahelanthropus tchadensis (approx. 7 mya). On the other hand increase in cranial capacity occurs quite late in the fossil record: Homo habilis (approx. 2 mya) for example, while fully bipedal, had a brain size within the range of modern day gorillas. Counter to this, Cunnane et al have argued, that a transition of semiaquatic Hominina-forms from fresh water habitats in the hinterland of Africa to more alcalic and saline habitats in Eastern Africa, e.g. in the then sea-flooded Afar-triangle in modern Ethiopia, could have supported the increase in human brain size through an increased access to e.g. DHA and iodine rich foods. It is argued, that molluscs, e.g. clams and oysters, as found along the shores of East Africa and in alcalic lakes along the Great Rift Valley has an optimal composition to support the extant human brain's nutritional needs. Proponents point to archaeological finds of shellfish kitchen middens as far back as in middle pleistocene some 164,000 years ago, during the earliest days of archaic Homo sapiens. Conversely, critics argue that landlocked humans without access to seafood develop normal brains and that these nutritional requirements can be met with a sepcific terrestrial diet. The encephalization of early Homo species is also argued as having been possibly driven by the consumption of hunted or scavenged animal brains supplying large amounts of scarce nutrients including docosahexaenoic acid. Reproduction: Morgan and others point to the increased adiposity of human infants, a marked difference from the offspring of other great apes. THis is suggested as an adaptation to increased insulation and buoyancy in water for human babies. It is pointed out, that vernix caseosa, a cheesy varnish coating the skin of newborn babies, apart from humans so far has only been observed on the cups of a few pinniped species, harbour seals. It is pointed out, that infant humans cannot walk upright, untill as much as one year of age, completely unknown among simian offspring, e.g. grassland-dwelling baboons. Morgan also claims, that newborns are adequately suited to swim along with their mother, while being able to hold their breath upwards of 45 seconds. Historically, women throughout the world have experienced a series of potentially life-threatening circumstances delivering above water, while Morgan and others, e.g. the French physician Michel Odent, point to recent decades of studies into baby swimming and water birth, which is argued to relieve stress and pain effects for both mother and child, with no corresponding observed drowning risks for the child. Morgan also points to unique features of both men and women's genitals, and the woman's protruding, fat-filled bosom as possible aquatic adaptations, with alleged convergence observed in sirenia. Presented criticism to these claims include the infant's increased risk of drowning if parting from its mother, coupled with observations of both young children as well as adults developing aquaphobia, while baby swimming and water birth are being rejected as fads. Ethological claims Habitat: Proponents of AAH argue, that the concentration of the contemporary world population of more than 7 billion people illustrates a trend for Homo sapiens to cling together in coastal regions alongside river valleys, lakes and seashores, in modern times particularly in India and China. Critics argue that this cannot disclose a similar trend in the eon long development of Homo, as modern human urbanization is said to be dependent on easier transit routes, this including rivers and seas. Conversely, Morgan argues, that humans have a similar preference for recreation sites along said coastal regions, e.g. tropical beaches. Human bathing behavior is argued as a remnant of recent semiaquaticism. Bathing behavior: Across the globe, humans employ hygiene bathing, this regardless of faction, ethnicity, gender, etc. This is argued as a behavioral relic of a semiaquatic stage. As an offshoot to the argument that other traditional terrestrial mammal groups may also be past semiaquatics, similar behavioral traits in both African and Asian elephants, which are also observed bathing regularly with its whole body submerged. Other claims Rare presented AAH-arguments points to the human tendency to watery psychic tears, and also sweat to cool down, where Morgan has withdrawn previous arguments, seeing that horses is a rare mammal species to also sweat profusely. It is occasionally argued, that humans compared to other apes have reduced olfaction, with claimed convergences observed in other aquatics, e.g. whales; that the protuding human nose would be adapted to keep splashes out of nasal cavities, arguing the semiaquatic proboscis monkey or semiaquatic tapirs as possible convergences; the tendency of partial to full baldness in men; the tendency for human obesity; and that human kidneys are better suited for excretion of salt than other apes. Such arguments are generally considered more speculative and is often heavily critized. Theoretical considerations Critics of AAH note, that the descended larynx is not exclusive to humans in terrestrials, but also found in red deers. Elaine Morgan retracted an early AAH-argument of human sweating being an aquatic indicator after critics cited, that also horses sweat. The AAH has been criticized for containing multiple inconsistencies and lacking evidence from the fossil record to support its claims (Morgan, for instance, failed to discuss any fossils found after 1960 and much of her analysis is by comparing soft tissues between humans and aquatic species). It is also described as lacking parsimony, despite purporting to be a simple theory uniting many of the unique anatomical features of humans. Anthropologist John D. Hawks expresses the view that rather than explaining human traits simply and parsimoniously, it actually requires two explanations for each trait - first that proximity to water drove human evolution enough to significantly change the human phenotype and second that there was significant evolutionary pressure beyond mere phylogenetic inertia to maintain these traits (which would not be adaptive on dry land) and points out that exaptation is not an adequate reply. Hawks concludes by saying: In other words, the Aquatic Ape Theory explains all of these features, but it explains them all twice. Every one of the features encompassed by the theory still requires a reason for it to be maintained after hominids left the aquatic environment. Every one of these reasons probably would be sufficient to explain the evolution of the traits in the absence of the aquatic environment. This is more than unparsimonious. It leaves the Aquatic Ape Theory explaining nothing whatsoever about the evolution of the hominids. This is why professional anthropologists reject the theory, even if they haven't fully thought through the logic. Ellen White describes Morgan's work as failing to be empirical, not addressing evidence that contradicts the hypothesis, relying on comparative anatomy rather than selection pressure, not predicting any new evidence and failing to address its own shortcomings. White stated that while the hypothesis had the scientific characteristics of explanatory power and public debate, the only reason it has received any actual scholarly attention is due to its public appeal, ultimately concluding the AAH was unscientific. Others have similarly noted the AAH "is more an exercise in comparative anatomy than a theory supported by data." Though describing the hypothesis as plausible, Henry Gee went on to criticize it for being untestable, as most of the evolutionary adaptations described by Morgan would not have fossilized. Gee also stated that, while purely aquatic mammals such as whales show strong skeletal evidence of adaptation to water, humans and human fossils lack such adaptations (a comment made by others as well); that there are many hypothetical and equally plausible scenarios explaining the unique characteristics of human adaptation without involving an aquatic phase of evolution; and that proponents are basing arguments about past adaptations on present physiology, when humans are not significantly aquatic. There is ultimately only circumstantial evidence to suggest, and no solid evidence to support the AAH. ScienceBlogs author Greg Laden has described the AAH as a "human evolution theory of everything" that attempts to explain all anatomical and physiological features of humans and is correct in some areas only by chance. Laden also states that the AAH was proposed when knowledge of human evolutionary history was unclear, while more recent research has found that many human traits have emerged at different times over millions of years, rather than simultaneously due to a single evolutionary pressure. Evolutionary biologist Carsten Niemitz states that he believes the AAH as expressed by Morgan didn't fulfill the criteria of a theory or a hypothesis, merely "[listing] analogies of features of savannah type mammals on the one hand and of aquatic mammals and man on the other, asking the scientific community for explanations other than a common aquatic ancestor of extant man." Marc Verhaegen has also challenged the AAH as expressed by Morgan, believing the ancestors of apes as well as humans may have had their evolutionary history influenced by exposure to flooded forest environments, and that based on the hominin fossil record, regular part-time underwater foraging began in the Pleistocene rather than the early Pliocene as Morgan’s model proposes. In 2012 Langdon reviewed an e-book published by Bentham Science Publishers collecting 50 years of theorizing about the AAH. In his review, Langdon noted the lack of a single "aquatic ape hypothesis", instead there are multiple hypotheses with a common theme of evolutionary pressure due to dependence on an aquatic habitat. While original versions thought to explain an apparently substantial gap between humans and closely related common ancestors, more recent variants of these hypotheses have had to adjust to the fact that the gap was more apparent than real and the significant commonalities found between humans and other African apes. Three main strands of thought now exist regarding the AAH, varying according to when the theorized aquatic phase occurred - from the Middle Miocene to approximately three million years ago (Hardy's original model, which was based on a large gap in the fossil record that has since been filled in), from the Early Miocene when ancestral hominids were thought to wade in costal swamps and from which Homo species were thought to split off and adapt to swimming and diving (associated with the work of Marc Verhaegen), and from 200,000 years ago when exploitation of costal resources led humans out of Africa and resulted in the evolution of modern humans (associated with the work of Algis Kuliukas). Langdon notes the strong associations of humans with water, as well as the adaptability of the species to incredibly diverse ecological niches (including costal and wetland regions), both within and across lifetimes. Whether these associations define humans as "semiaquatic" or not "represents a fundamental point of departure between anthropologists and the [Aquatic Hypothesis] community." Langdon notes the three lines of evidence cited to support the AAH (comparative anatomy between humans and other semiaquatic species; hypothetical situations in which evolutionary pressure might have produced convergent evolution between humans and semiaquatic species; the ability for humans to perform various activities in the water) and concludes about these lines of evidence, These rhetorical strategies create long lists of claims, but until each hypothesis is independently established, it does not constitute evidence for an aquatic scenario. At best it shows consistency with a prior assumption. Evolutionary convergence – structural similarity – by itself is a metaphor for functional similarity. Metaphors are useful, but they demand that we examine points of resemblance closely in order to learn whether they are meaningful. Like metaphors, evolutionary convergences have their limits: eventually differences will emerge. Dolphins and humans are similar in the loss of body hair, relatively large brains, and complex vocal capacities; but these similarities do not make us dolphins. Nor is it clear which, if any of these similarities are related to water. Each trait must be investigated and resolved as a separate functional and evolutionary question. Unproven suppositions cannot serve as evidence for other hypotheses. Langdon criticizes the alleged "parsimony" of the AAH irrelevant as it is used to generate hypotheses about human adaptation – but does not prove them. The AAH is, like many Just So Stories in anthropology, ignored less because of prejudice than because of a lack of empirical evidence to support it, because it engages only with supporting evidence in the relevant scientific literature while ignoring the larger body of unsupporting evidence, and because its hypotheses are portrayed as "compatible with" more accepted hypotheses and thus unable to distinguish between or provide explicit evidence for the AAH. Langdon concludes his review: It is now incumbent upon both authors and critics to clarify the assumptions with which they are working and, where possible, to make empirically testable predictions. Similarly, the many gloating references in this book to the collapse of the Savannah Hypothesis should not suggest that all terrestrial models have been challenged. Possibly the time has come to bring the “paradigms” together; to step out of the “us vs. them” mentality held by both sides of this debate; and simply to recognize that dozens of speculative hypotheses for human evolution exist in the literature that may or may not discuss a relationship with water. The authors of the volume published a reply. Reception The AAH has received little serious attention or acceptance from mainstream paleoanthropologists, has been met with significant skepticism and is not considered a strong scientific hypothesis. The AAH does not appear to have passed the peer review process, and despite Morgan being praised by various scholars, none of her work has appeared in any academic journals of anthropology or related disciplines. The AAH is thought by some anthropologists to be accepted readily by popular audiences, students and non-specialist scholars because of its simplicity. In 1987 a symposium was held in Valkenburg, the Netherlands, titled "Aquatic Ape: Fact or fiction?", which published its proceedings in 1991. A review of Morgan's book The Scars of Evolution stated that it did not address the central questions of anthropology – how the human and chimpanzee gene lines diverged – which was why it was ignored by the scholarly community. The review also stated that Morgan ignored the fossil record and skirted the absence of evidence that australopithecine underwent any adaptations to water, making the hypothesis impossible to validate from fossils. Morgan has claimed the AAH was rejected for a variety of reasons unrelated to its explanatory power: old academics were protecting their careers, sexism on the part of male researchers, and her status as a non-academic intruding on academic debates. Despite modifications to the hypothesis and occasional forays into scientific conferences, the AAH has neither been accepted as a mainstream theory nor managed to venture a genuine challenge to orthodox theories of human evolution. Morgan's critics have claimed that the appeal of AAH can be explained in several ways: The hypothesis appears to offer absolute answers, which appeals more to students and the public than the qualified and reserved explanations offered by mainstream science. Unusual ideas challenge the authority of science and scientists, which appeals to anti-establishment sentiments. The AAH as developed by Morgan has a strong feminist component, which particularly appeals to a specific, feminist audience. The AAH can be explained simply and easily, lacking the myriad details and complicated theorizing involved in dealing with primary sources and materials. The AAH uses negative arguments, pointing to the flaws and gaps in conventional theories; though the criticisms of mainstream science and theories can be legitimate, the flaws in one theory do not automatically prove a proposed alternative. The consensus views of conventional anthropology are complicated, require specialized knowledge and qualified answers, and the investment of considerable time to understand. John D. Hawks, along with PZ Myers and fellow ScienceBlogs paleontologist Greg Laden recommend the website "Aquatic Ape Theory: Sink or Swim?" by Jim Moore as a resource on the topic. Conversely, Elaine Morgan and Algis Kuliukas have critisized Jim Moore for heavily distorting in particular Morgan's arguments, this with very little use of references. Anthropologist Colin Groves has stated that Morgan's theories are sophisticated enough that they should be taken seriously as a possible explanation for hominin divergence and Carsten Niemitz has found more recent, weaker versions of the hypothesis more acceptable, approaching some of his own theories on human evolution. In a 2012 paper, anthropologist Philip Tobias noted that rejection of the AAH led to stigmatization of a spectrum of topics related to the evolution of humans and their interaction with water. The result of this bias, in his and co-authors' opinions, was an incomplete reconstruction of human evolution within varied landscapes. See also Endurance running hypothesis Footnotes External links Template:DMOZ – other web resources Scars of Evolution, podcast of two part BBC Radio 4 feature on AAH, broadcast in 2005 Presentation by Elaine Morgan at TED July, 2009; Comment on ScienceBlogs by paleoanthropologist Greg Laden

Suggestion - new subsection - anthropological consensus on human evolution

I'm still trying to do something about this hopeless, negatively biased article. I propose to lead the section about the actual hypothesis/ses by summarizing the contemporary consensus on human evolution, as expressed by the scientific field of anthropology. This is to illustrate the background for Elaine Morgan's AAH, since she based her work on what she perceived as shortcomings to parts of that consensus, straw man arguments and whatnot. Whether we then further detail her challenging of this consensus in the following sections is for a different discussion. If you skeptics really desire an optimal, non-POV article detailing what the hell all this boohah is about, let's start with this, since it should contain the fewest controversies (unless creationists are also hanging out in here, which is not bloody unlikely the way things have been going).

Suggestion

Background - anthropological consensus on human evolution Family tree showing the extant hominoids: humans (genus Homo), chimpanzees and bonobos (genus Pan), gorillas (genus Gorilla), orangutans (genus Pongo), and gibbons (four genera of the family Hylobatidae: Hylobates, Hoolock, Nomascus, and Symphalangus). Great Rift Valley in East Africa, key to human evolution. File:Paranthropus on Plains art.jpg A classic depiction of the consensus on the earliest evolution of hominins in East Africa, here Paranthropus. See also: Human evolution Modern humans, Homo sapiens, developed from earlier forms found as fossils at various locations around the world, seeing an early concentration in East Africa. Other remnants from early humans such as tools, foods, dwellings, etc., have also been detected. Combined, these finds present a partial image of the process, that developed the species Homo sapiens. From the collective work of anthropology, and in later years also genetics, established consensus states, that humans belong in the biological tribe Hominini, this in the family of Hominidae (the great apes), this in the order of primates, this in the class of mammals. Humans are closely related to, in order of closest kinship, the great ape genera chimpanzees, gorillas, orangutans, and further distant the family of gibbons. Hominini includes the subtribe Australopithecina with the genera Sahelanthropus, Orrorin, Ardipithecus, Paranthropus, Australopithecines; and the subtribe Hominina, encompassing the genus Homo, some of its species being Homo habilis, Homo ergaster, Homo erectus, the Neanderthals and modern humans, the latter being the only extant species. There is still some uncertainty about the interrelation between the known Hominin fossils; new finds can still drastically rewrite the human family tree, most recently with Sahelanthropus. Contemporary anthropology estimates, that the direct ancestors of modern humans split from a common ancestor to chimpanzees somewhere between 4 and 8 million years ago in Africa; the fossil ape Sahelanthropus tchadensis which lived some 7 million years ago in Chad is considered the earliest possible homininin. Since the breakthrough of Darwin and Wallace's theory of evolution in the 19th century, it has been debated why humans have features that distinguish them from their nearest evolutionary relatives; most notably by being near-furless, employing upright bipedal stance on their hind limbs, and having the perhaps most complex brain in the animal kingdom. A wide range of difficult to corroborate hypotheses have been presented as to the evolutionary background of the unique features of modern humans; for human bipedalism e.g. altered carrying behavior, improved energy efficiency, improved thermal regulation, altered social behavior and increased dominance behavior. The human split from the lineage of the chimpanzees is linked to the geological formation of the East African mountain range Great Rift Valley that extends from Djibouti to Mozambique. In this region are found many of the key fossils of the earliest hominins, leaving it to be considered the cradle of humanity. The most widely considered hypothesis is that woodland dwelling, brachiating hominoids, specifically on the eastern side of the mountain range, gradually lost their habitat to more open areas, for instance grasslands, and that this and other changes forced these hominoids to develop the shapes, that gradually resulted in modern humans. In recent decades, the traditional image of human origin having taken place in grasslands (e.g. the African savannah) has been challenged, since particularly the oldest homininin fossils are found alongside fossilized fauna and flora from traditional woodland habitats, rather than from grasslands, e.g. the some 4.4 million year old fossil Ardi, an Ardipithecus ramidus.

Summary diagram

I have added a diagram as a summary of the arguments proposed under the AAH. This is to supplement the main text since some people complained there is not enough description of the hypothesis itself. I've added the caption to avoid misleading the readers that they are facts. Comments and suggests are welcomed!

I've also uploaded a similar diagram in the Endurance running hypothesis page.

A few notes:

• The diagram demonstrates the arguments proposed in the aquatic ape hypothesis (AAH) and related water-based models (e.g. the shore-based diet model), that swimming, diving, and a semi-aquatic lifestyle may have influenced human evolution, caused numerous adaptations in human morphology, anatomy and physiology.
• This diagram is a plain description of the hypothesis and does not provide any support nor criticism to the arguments.
• It must be noted that the points listed are not facts, but hypothetical claims that require further scientific investigations to verify their accuracy, falsifiability, and relevance to human evolution.

Chakazul (talk) 10:32, 31 October 2013 (UTC)

I am not happy with diagrams like this. They are hard to edit and present things without citations. Diagrams set up by editors should illustrate what the text says. Dmcq (talk) 12:34, 28 December 2013 (UTC)

Hi, You may notice that all points in the diagram are cited, referring to the reference list below. I expect there is no significant difference between the diagram and the text, or else something may be missing in either side.

Please tell me if you have comment on any specific point or the overall presentation, I will try my best to edit it. Chakazul (talk) 16:29, 30 December 2013 (UTC)

My objection is about the whole concept of such diagrams in Wikipedia. We shouldn't have things which give a whole lot of facts in a picture and are hard to change. And no I don't want you around to do the changing. This is just against the idea of an encyclopaedia that everyone can edit. Also a picture gives undue weight as in a picture is worth a thousand words. The words and citations are what should be important and the illustrations subsidiary. Dmcq (talk) 16:34, 30 December 2013 (UTC)

I'll have a look around to see where I can register my objectio nproperly as doing so on a particular page is not the right way to go around such things. Dmcq (talk) 16:40, 30 December 2013 (UTC)

I have raised my concerns at Wikipedia:No_original_research/Noticeboard#Infographics Dmcq (talk) 22:42, 31 December 2013 (UTC)

I don't think there is much need of editing the diagram, since these are the original claims of the hypothesis, either future search will endorse or reject any of them, they will remain as the original claims. Unless there're typos or wording problems which would be easier to edit. Anyway, let's discuss in the noticeboard. Chakazul (talk) 11:02, 2 January 2014 (UTC)

Consider also the accessibility implications of such images; how is their content made available to, for example, blind people who have pages read to them by assistive software? Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 22:57, 31 December 2013 (UTC)

Blind people can just read the main text. This diagram is a kind of visualization, the content is expected to be the same as the text. Chakazul (talk) 11:02, 2 January 2014 (UTC)

I was assuming all the points were also in the text. The main problem I feel as I've said at the NOR noticeboard is that it is an overall synthesis which advances a position rather than just being an illustration of a point. I have a numbe rof other objections as I say above about being hard to edit but this business about SYNTH is why it is raised at the OR noticeboard rather than the NPOV one. Even if it wasn't a fringe topic I'd still feel this advanced a point of view with a synthesis. This is mainly why I disagree with this illustration but don't object to the other illustrations like the baby in the water at the top which illustrates particular points. Dmcq (talk) 15:39, 2 January 2014 (UTC)

It appears that a "big picture" or synthesis is making a favor for the hypothesis, but not necessary... some consider this a weakness as being an "umbrella" hypothesis that trying to explain too much. As in Endurance running hypothesis, even I personally don't endorse that hypothesis, such a diagram helps me to evaluate it as a whole and easier to find something. To put it more extreme, we can certainly illustrate what creationists / ID proponents claimed into a beautiful infographics, and appreciate its level of absurdity at the same time. Chakazul (talk) 04:52, 3 January 2014 (UTC)

It is undue though, where is the big picture for the mainstream? And it is hard to link each point to the particular point and its discussion in the text. When individual illustrations are used they are just beside the relevant text with the discussion of them to ameliorate the undue part. The synthesis pushes just one point of view. Dmcq (talk) 19:54, 4 January 2014 (UTC)

Chakazul, what I think you have done is created a WP:POVFORK of the article, and encapsulated it in a form which makes it very difficult for anyone except you to edit. (I think your work, and info-graphics generally, would be appreciated at other venues, like IFLS to name one example, yet is against the spirit of wikipedia. Besides, such a huge quantity of text - regardless whether you try to name it a "summary" - should be laid out in a table since nobody can read the thumbnail version, many people also won't be able to read a larger version either for accessibility or display-device-resolution reasons, and in effect it is circumventing our Manual of Style both generally and also specifically: WP:MOS#Avoid_entering_textual_information_as_images.) Cesiumfrog (talk) 22:34, 4 January 2014 (UTC)

Short full protection

I have fully protected this article for 3 days in order to halt the current edit war. CIreland (talk) 20:44, 4 January 2014 (UTC)

Removal of all illustrations

I had a problem with one of the illustrations here as detailed in the previous section, but a bunch of people have descended on it and removed all of them without discussion. The last says 'one edit is not edit warring and this is the last stable version so per WP:BRD this is the one we go with while talk page discussion commences' but it is obvious that is not so if one looks at the history pager, most of those illustrations have been there and never removed in the last few months at least before today. Perhaps some of these people could say why they have suddenly turned up? And what is the reasoning for removing all illustrations? Dmcq (talk) 20:46, 4 January 2014 (UTC)

It's at ANI. Also, the three tags just added all mention discussion. It would help if the editor adding those tags actually discussed their objections to specific content. --NeilN ^{talk to me} 21:14, 4 January 2014 (UTC)

Thanks, that explains it. I wish one of them at least had contributed to the discussion here. Dmcq (talk) 22:09, 4 January 2014 (UTC)

I've argued for removal (of some images) at ANI. I think a few images - perhaps the first two - could be argued to be a positive, but the rest seem pointless. Black Kite (talk) 11:49, 5 January 2014 (UTC)

I wouldn't object overly to cutting out the more obvious ones. I think the baby in the water one is a good illustration for the overall topic. Dmcq (talk) 12:56, 5 January 2014 (UTC)

Yeah, the baby one is fine, and I'd drop the gorilla one down to the "hypothesis" section (where it also illustrates bipedalism). I can't see any point in the others. The horse, deer, shower and swimming ones are simply ridiculous. Black Kite (talk) 14:20, 5 January 2014 (UTC)

Dmcq: I've removed all images before, but persistent advocates keep adding them back. As several others have pointed out, at least the majority of these "illustrations" are unecyclopedic. As Engelbrecht himself pointed out on ANI, most of them are used to "illustrate" various arguments and could be used in a lot of articles to "make a point". (Here is an example from The Guardian: Aquatic apes are the stuff of creationism, not evolution (Don't miss the elephant joke at the end.)) None of them addequately explain AAH. For this reason, neither the baby nor the gorilla belong here. There are illustrations online that specifically illustrates AAH. Get one or wait for one.

Per WP:LEADIMAGE: "Lead images should be images that are natural and appropriate visual representations of the topic; they not only should be illustrating the topic specifically, but should also be the type of image that is used for similar purposes in high-quality reference works, [...]"

--Fama Clamosa (talk) 16:45, 5 January 2014 (UTC)

That others persist in putting in images and you persist in removing them is evidence of slow edit warring, nothing else. So some people agree with you and others disagree with you, that shows very little of use. Pointed out is simply emphasising your side. I know the hypothesis is not mainline, it is hardly creationism but even it it were I fail to see the relevance. As to a lead image the article you pointed to at the Guardian shows exactly that type image, so fulfills your requirement that the lead image be representative of the type used not thhat that is required, it is simply a guideline. Dmcq (talk) 16:59, 5 January 2014 (UTC)

Dmcq: It's not "that type of image", it's the same image, used in the same "illustrative" purpose. Did you even try to see the irony in the Guardian? Are you saying Wikipedia guidelines don't apply to this article? --Fama Clamosa (talk) 23:19, 5 January 2014 (UTC)

So what's the problem if they though it was okay as an illustration? Does the irony content mean you can use the article to support whatever you like but it can't be used for anything you don't like? And if you're quoting guidelines then perhaps you could point to the particular sections of them. Were you referring to me saying that it was a guideline rather than a policy? I already said it satisfied the guideline. The business about being a guideline is that it gives advice on best practice, it does not imply that anything deviating in the slightest must be removed. As WP:POLICY says it should be treated with commonsense. Dmcq (talk) 23:37, 5 January 2014 (UTC)

Also note that Fama feels the need to ridicule AAH by pointing to an absurd blog analogy about elephants with yellow feet (elephants which are old semiaquatics too, by the way). Isn't that typical behavior among creationists haranguing evolution? --CEngelbrecht (talk) 21:09, 5 January 2014 (UTC)

You didn't say anything pertinent to improving the article. Attacking other editors got you at ANI just recently and didn't help your case. Please just discuss the subject and not the editor. Dmcq (talk) 22:40, 5 January 2014 (UTC)

Unless a guy like me is attacked as an editor, right? Because I dare to have read the sources to this idea, instead of watching some mockumentary about mermaids on Animal Planet and go, "Yep, that's what that idea is about." Because I've personally concluded, that AAH is not unreasonable thinking, now that we all "know" that it's wrong for all eternity. Then I've just asked for the urine, haven't I, you hypocrite?

And the hypocrisy is even deeper with the random arguments for getting rid of illustrations here. One user argues, that a generalized image of the various AAH hypothesis arguments is unnecessary, because the listed points are only partially covered in the body text. Another says, that any images are unnecessary, because the points are described in the body text. Are pictures supposed to illustrate something key from the body text, or something not represented in it? I hear both, all of a sudden.

But we're not talking about use of illustrations here. Those images were removed, because the user in question becamse uncomfortable being presented with thousand-words images of an idea, they've been accustomed to laugh at for all the wrong sociological reasons. Reasons which is comparable to the ones that plagued great thinkers like Copernicus and Galileo, and to an extent still Darwin. Even if AAH is wrong, they don't even want it to be presented as the reasonable concept it is. 'Cause the human ape don't want to know what it is. And in that, they are no different in psychology than the creationists and ID'ers plaguing the articles on evolution.

'Cause this stripping of all imagery is just another typical mistreatment of this article. Over these last few years I've seen the article's body text reduced to nothing, where the only focus winded up being "this idea is nuts, go back to sleep". Close to all description of the individual arguments deleted, where it was nothing of an encyclopedic entry. A typical non-POV presentation based from pure negative bias. And I've seen continous harassment against users adding neutral wordings against this negative bias, again on par with the methods of creationists and ID'ers against evolution describing users. I've seen nothing but a continous pressure for censorship. For some odd pshychological reason, a certain group just don't want this idea to be out in the open. This is the general type of conduct, this fringe idea brings out in not the support, but the opposition. All this not about how to use images. This is about a continous vandalising behavior, that only seeks to kill a non-POV presentation of a divisive idea. Because a range of people just don't "like" it.

I see all this as a big threat to scientific thought and the well-intended purpose of Wikipedia. Enough is enough. If AAH is so bloody wrong, a neutral presentation would support that anyway. But that is not good enough, is it? (Partially copied from "ANI") --CEngelbrecht (talk) 23:44, 5 January 2014 (UTC)

The village pump is probably the right place for discussions like that. Dmcq (talk) 00:00, 6 January 2014 (UTC)

How about the gorilla picture in the lead then if there is some unspecified thing wrong with the baby one. It is rather like one I saw on another discussion about the topic [2]. Or is it unacceptable to use something similar to that article too because of some unspecified guidance? Dmcq (talk) 23:57, 5 January 2014 (UTC)

There isn't anything wrong with any of the pictures included. Except that they don't support the general misconception, that the aquatic ape hypothesis is a laghuable idea. I'm very sorry, but a balanced non-POV, neither positive or negative biased version using adequate, sourced body text and illustrations just can't support that foolish custom thinking. Even if the damn thing should be wrong and humans have never been bathing apes. --CEngelbrecht (talk) 00:12, 6 January 2014 (UTC)