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Saturday, July 24, 2010
Monday, July 12, 2010
The Aquatic Ape
Since Raymond Dart's 1924 discovery of the first ever australopithecine fossil, Australopithecus africanus, anthropology and the course of evolution has endured a perspective dominated by the hegemonic view come to be known as the Savannah Hypothesis. As the fossil record gained momentum, the view became solidified that the transition from ape to hominid proceeded in response to climatic conditions caused by a the recession of forested area. Our ape ancestors allegedly left the dwindling tree habitat in favor of the contemporaneously widespread grasslands and savannahs. This change of habitat, it is supposed, was the impetus for the behavioral and concomitant physiological changes that led to these woodland apes eventually becoming human. However, there has been a more recent call for a paradigm shift in our anthropological understanding. The Aquatic Ape Hypothesis has gained some support, as it holds that it more deftly accounts for anthropological development while not being mutually exclusive from the Savannah Hypothesis. However, as the hypothesis was first put forth in a 1960 article by marine biologist Alister Hardy and more maturely developed by the writer Elaine Morgan (from outside the scientific community altogether), it remains largely castigated from within the academic anthropological community. Nonetheless, the Aquatic Ape Hypothesis seems to succinctly account for seven points of departure that are hallmarks of the hominid:
Contrary to the claims of the recession of forest area and increase in open savannah providing the impetus for evolutionary changes in our ancestors, the picture seems rather incomplete. Our reliable fossil evidence begins with Australopithecus at about 3.5 million years ago. Prior to this, we have sparse remnants of Sivapithecus which lived between 12.5 and 8.5 million years ago, yet in-between is a great void. Our understanding of climatic conditions during this "void" indicates that sea levels rose considerably in the north of Africa, inundating expanses and isolating forested areas as islands. The Aquatic Ape Hypothesis suggests that apes marooned on these tracts of forest, with dwindling resources, very well could have taken to the sea in order to supplement their needs. This would have spawned the chain of events that would lead our ancestors on a unique path into the sea only to return upon the sea's retreat. Yet, to gain credibility, we will need to analyze how the hypothesis explains the course of hominid evolution.
The Savannah Hypothesis best explains the loss of body hair in the hominid as a function of two factors. The first factor is the emergence of game hunting causing a potential for overheating, leading to hair loss and sweating to keep the body cool. The second factor suggests that the problem of hair dwelling parasites and related diseases would be eliminated were hairlessness naturally or sexually selected. However, both factors have no parallels. It seems a curious state of affairs for nearly all African mammals to maintain their fur with the exception of mud and water "wallowers." This may be taken as a case in point in perpetuating the fallacy that hair only insulates heat - in fact, the hair maintains temperate air close to the body, warding off excessive heat as well as cold. It might be noted that the vast majority of "naked" mammals are those that have followed a course to becoming fully aquatic or wallowers. These would include: cetaceans (whales, dolphins, and porpoises), sirenians (manatees, dugong, etc.), hippopotamuses, elephants, and rhinoceroses. Further, it may be noted that sweating is a maladaptive trait for the open savannah, depleting the body rapidly of essential water and the electrolyte sodium.
One of the instrumental factors in Alister Hardy first positing an aquatic episode in hominid evolution was the deposition of energy in subcutaneous fat - a ubiquitous characteristic amongst aquatic mammals and one particular to humans as a terrestrial mammal. The Savannah hypothesis best explains subcutaneous fat as a reaction to hairlessness; the cooling mechanism proved to be too successful, necessitating fat to keep the body warm enough. This seems rather careless when considering the fact that humans maintain all of the hair follicles and very well could re-evolve a coat for warmth. Nonetheless, subcutaneous fat is a characteristic in aquatic mammals that seems to aid in buoyancy as well as insulation against the perils of water temperatures. In fact, it seems rather maladaptive for some whale species that dive to great depths and would find the buoyant nature of the fat to be a hindrance, yet would still provide the benefit of insulating body heat effectively. It may be noted that in human newborns, the extent of their fatty tissue stands in great contrast to other primates.
Although all mammals have tear glands which bathe the eyeball in a protective saline solution, no other terrestrial mammals exhibit the phenomenon we can call weeping. Though other mammals may howl and whimper, even our closest primate "relatives" lack the tears we associate with it. The only phenomenological cognate amongst mammals occurs in pinnipeds (seals) which display tears in times of distress. Curiously, sea birds contain nasal glands similar to our tear glands that drain fluid. In 1956 a study was conducted in which cormorants were fed sea water via feeding tube at 6% of their body weight. The motivation for the study was to observe how a diving bird could manage incidental ingestion of sea water. As expected, the cormorants were found with higher concentrations of soduim in the urine, yet a surprising discovery was the nearly pure sodium content excreted from the cormorants' nasal glands. It isn't difficult to extrapolate that our hominid ancestors could have developed a similar, convergent evolutionary coping mechanism to rid the body of ingested excess sodium in sea water. This mechanism for dispensing waste product could have later been modified for further ridding the body of chemical wastes produced by stress responses.
Bipedalism is often suggested as a result of leaving the hands free to carry tools and the need to see farther in the high brush of the grasslands. However, barring a counterbalancing tail, a phenomenon of locomotion emergent only one time in biological history seems suspect, surely others in the same habitat would follow some convergent evolutionary trait. Also, it seems counter-intuitive for the freeing of the hands to be any sort of evolutionary impetus. We can see from chimpanzees and other knuckle walking apes with whom we share a common ancestor, they are quite adept at maintaining a grasp on objects during locomotion. Further, the fossil record indicates that bipedalism was present in the Australopithecus yet tool-making was not mastered for nearly another two million years with Homo habilis. Although most primates seem to have a fear of water, wading upright has been witnessed specifically in different macaque species naturally in hunting for sea food or washing food in a controlled experiment. This is analogous to the claim that Alister Hardy first presented as an impulse toward bipedalism: advancing into the sea would not permit one to venture very far as a quadruped, it would be natural to proceed on two. However, when swimming, the natural reaction is to take a horizontal orientation. It is likely that this coupled with the penchant for wading would provide a natural impetus for skeletal realignment of the spinal and pelvic adaptations we see as a predisposition for bipedalism. Of course, this taking place within water would not come with the precarious question of balance on terra firma.
Ventro-ventral copulation, or belly-to-belly, is a practice seldom found in any other primate. Perhaps the only exception is the bonobo (though it is not a regular and common practice therein). Nonetheless, human anatomical study informs us that ventro-ventral copulation is a coital position for which humans are adapted; the vaginal canal is angled to accommodate this position, an attribute unique to hominids and no other primate. The Savannah Hypothesis proffers that the physiological and behavioral adaptation are such as to enhance pair bonding. However, many other primates practice pair bonding and yet we do not see the advent of ventro-ventral copulation. It has been observed amongst whales, dolphins, seals, manatees, and other aquatic mammals that ventro-ventral copulation is veritably the norm, one with which humans conform, particularly within the perspective that humans underwent an aquatic episode before returning to land.
It is often conjectured that human swimming is strictly a cultural, nurture phenomenon. However, in the same manner we now accept speech and language to be partially hardwired yet transmitted culturally, it is not far fetched to suppose the same for swimming. Many claim that primates have an innate fear of water that is distinct among mammals and swimming is not natural to humans. However, the proboscis monkey, found in the swamplands of Borneo, has been found miles out at sea. Also, the talapoin, a monkey native to central Africa dives into water as a defense strategy. Of course, there are physical and behavioral observations that aid in understanding the human penchant for water. The human nose has nostrils that differ quite remarkably from other primates. One might suppose human nostrils to present a splash shield. Also, the position of the larynx in the human permits breath control not found in other primates. The human capacity for "holding ones breath" is rather unique. The most controversial evidence stems from research begun by Russian gynecologist Dr. Igor Tjarkovsky on infants in the 1960s. Before being condemned and shut down by the USSR Ministry of Public Health, Tjarkovsky pioneered underwater childbirths, now a growing trend in natural births. Tjarkovsky's observations began on his premature daughter who barely weighed over two pounds. Putting her in warm baths, rationalizing it to be simulation of the amniotic fluid, he found that at three months, she was able to hold her breath up to three minutes under water without any adverse effects. Noting a remarkable development in his daughter, Tjarkovsky then went on to incorporate these techniques into his practice. Infants, have been found to exhibit reflexes to not breathe when submerged as well as "ipsilateral flexions" which amount to swimming motions of the arms.
One of few traits that are markedly distinctive of humanity is the capacity for speech and language. The Savannah Theory best accounts for the development of speech as a manner of instructive communication in the making of tools and/or a measure of coordination in big game hunting. Nonetheless, many terrestrial animals hunt cooperatively without the use of verbal communication. Also, it seems odd for communication to follow a verbal track rather than the already highly developed visual one in terms of tool-making instruction. However, we can gather primates, particularly our closest relatives to be social by nature. Upon that presumption, if we then posit the Aquatic Hypothesis, it then follows that the exigencies of locomotion in water would prevent effective visual, tactile, or olfactory communication and facilitate a need to develop a vocal form. Unequivocally, other aquatic mammals have displayed a convergent evolution to harbor vocal capabilities. Namely, dolphins, whales, and the Ross Seal all have been documented to use vocal communication and echolocation under water.
- Loss of body hair
- Subcutaneous fat
- Tears
- Bipedalism
- Ventro-vental copulation
- Swimming/diving
- Speech
Contrary to the claims of the recession of forest area and increase in open savannah providing the impetus for evolutionary changes in our ancestors, the picture seems rather incomplete. Our reliable fossil evidence begins with Australopithecus at about 3.5 million years ago. Prior to this, we have sparse remnants of Sivapithecus which lived between 12.5 and 8.5 million years ago, yet in-between is a great void. Our understanding of climatic conditions during this "void" indicates that sea levels rose considerably in the north of Africa, inundating expanses and isolating forested areas as islands. The Aquatic Ape Hypothesis suggests that apes marooned on these tracts of forest, with dwindling resources, very well could have taken to the sea in order to supplement their needs. This would have spawned the chain of events that would lead our ancestors on a unique path into the sea only to return upon the sea's retreat. Yet, to gain credibility, we will need to analyze how the hypothesis explains the course of hominid evolution.
1. Loss of body hair
The Savannah Hypothesis best explains the loss of body hair in the hominid as a function of two factors. The first factor is the emergence of game hunting causing a potential for overheating, leading to hair loss and sweating to keep the body cool. The second factor suggests that the problem of hair dwelling parasites and related diseases would be eliminated were hairlessness naturally or sexually selected. However, both factors have no parallels. It seems a curious state of affairs for nearly all African mammals to maintain their fur with the exception of mud and water "wallowers." This may be taken as a case in point in perpetuating the fallacy that hair only insulates heat - in fact, the hair maintains temperate air close to the body, warding off excessive heat as well as cold. It might be noted that the vast majority of "naked" mammals are those that have followed a course to becoming fully aquatic or wallowers. These would include: cetaceans (whales, dolphins, and porpoises), sirenians (manatees, dugong, etc.), hippopotamuses, elephants, and rhinoceroses. Further, it may be noted that sweating is a maladaptive trait for the open savannah, depleting the body rapidly of essential water and the electrolyte sodium.
2. Subcutaneous fat
One of the instrumental factors in Alister Hardy first positing an aquatic episode in hominid evolution was the deposition of energy in subcutaneous fat - a ubiquitous characteristic amongst aquatic mammals and one particular to humans as a terrestrial mammal. The Savannah hypothesis best explains subcutaneous fat as a reaction to hairlessness; the cooling mechanism proved to be too successful, necessitating fat to keep the body warm enough. This seems rather careless when considering the fact that humans maintain all of the hair follicles and very well could re-evolve a coat for warmth. Nonetheless, subcutaneous fat is a characteristic in aquatic mammals that seems to aid in buoyancy as well as insulation against the perils of water temperatures. In fact, it seems rather maladaptive for some whale species that dive to great depths and would find the buoyant nature of the fat to be a hindrance, yet would still provide the benefit of insulating body heat effectively. It may be noted that in human newborns, the extent of their fatty tissue stands in great contrast to other primates.
3. Tears
Although all mammals have tear glands which bathe the eyeball in a protective saline solution, no other terrestrial mammals exhibit the phenomenon we can call weeping. Though other mammals may howl and whimper, even our closest primate "relatives" lack the tears we associate with it. The only phenomenological cognate amongst mammals occurs in pinnipeds (seals) which display tears in times of distress. Curiously, sea birds contain nasal glands similar to our tear glands that drain fluid. In 1956 a study was conducted in which cormorants were fed sea water via feeding tube at 6% of their body weight. The motivation for the study was to observe how a diving bird could manage incidental ingestion of sea water. As expected, the cormorants were found with higher concentrations of soduim in the urine, yet a surprising discovery was the nearly pure sodium content excreted from the cormorants' nasal glands. It isn't difficult to extrapolate that our hominid ancestors could have developed a similar, convergent evolutionary coping mechanism to rid the body of ingested excess sodium in sea water. This mechanism for dispensing waste product could have later been modified for further ridding the body of chemical wastes produced by stress responses.
4. Bipedalism
Bipedalism is often suggested as a result of leaving the hands free to carry tools and the need to see farther in the high brush of the grasslands. However, barring a counterbalancing tail, a phenomenon of locomotion emergent only one time in biological history seems suspect, surely others in the same habitat would follow some convergent evolutionary trait. Also, it seems counter-intuitive for the freeing of the hands to be any sort of evolutionary impetus. We can see from chimpanzees and other knuckle walking apes with whom we share a common ancestor, they are quite adept at maintaining a grasp on objects during locomotion. Further, the fossil record indicates that bipedalism was present in the Australopithecus yet tool-making was not mastered for nearly another two million years with Homo habilis. Although most primates seem to have a fear of water, wading upright has been witnessed specifically in different macaque species naturally in hunting for sea food or washing food in a controlled experiment. This is analogous to the claim that Alister Hardy first presented as an impulse toward bipedalism: advancing into the sea would not permit one to venture very far as a quadruped, it would be natural to proceed on two. However, when swimming, the natural reaction is to take a horizontal orientation. It is likely that this coupled with the penchant for wading would provide a natural impetus for skeletal realignment of the spinal and pelvic adaptations we see as a predisposition for bipedalism. Of course, this taking place within water would not come with the precarious question of balance on terra firma.
5. Ventro-ventral copulation
Ventro-ventral copulation, or belly-to-belly, is a practice seldom found in any other primate. Perhaps the only exception is the bonobo (though it is not a regular and common practice therein). Nonetheless, human anatomical study informs us that ventro-ventral copulation is a coital position for which humans are adapted; the vaginal canal is angled to accommodate this position, an attribute unique to hominids and no other primate. The Savannah Hypothesis proffers that the physiological and behavioral adaptation are such as to enhance pair bonding. However, many other primates practice pair bonding and yet we do not see the advent of ventro-ventral copulation. It has been observed amongst whales, dolphins, seals, manatees, and other aquatic mammals that ventro-ventral copulation is veritably the norm, one with which humans conform, particularly within the perspective that humans underwent an aquatic episode before returning to land.
6. Swimming/diving
It is often conjectured that human swimming is strictly a cultural, nurture phenomenon. However, in the same manner we now accept speech and language to be partially hardwired yet transmitted culturally, it is not far fetched to suppose the same for swimming. Many claim that primates have an innate fear of water that is distinct among mammals and swimming is not natural to humans. However, the proboscis monkey, found in the swamplands of Borneo, has been found miles out at sea. Also, the talapoin, a monkey native to central Africa dives into water as a defense strategy. Of course, there are physical and behavioral observations that aid in understanding the human penchant for water. The human nose has nostrils that differ quite remarkably from other primates. One might suppose human nostrils to present a splash shield. Also, the position of the larynx in the human permits breath control not found in other primates. The human capacity for "holding ones breath" is rather unique. The most controversial evidence stems from research begun by Russian gynecologist Dr. Igor Tjarkovsky on infants in the 1960s. Before being condemned and shut down by the USSR Ministry of Public Health, Tjarkovsky pioneered underwater childbirths, now a growing trend in natural births. Tjarkovsky's observations began on his premature daughter who barely weighed over two pounds. Putting her in warm baths, rationalizing it to be simulation of the amniotic fluid, he found that at three months, she was able to hold her breath up to three minutes under water without any adverse effects. Noting a remarkable development in his daughter, Tjarkovsky then went on to incorporate these techniques into his practice. Infants, have been found to exhibit reflexes to not breathe when submerged as well as "ipsilateral flexions" which amount to swimming motions of the arms.
7. Speech
One of few traits that are markedly distinctive of humanity is the capacity for speech and language. The Savannah Theory best accounts for the development of speech as a manner of instructive communication in the making of tools and/or a measure of coordination in big game hunting. Nonetheless, many terrestrial animals hunt cooperatively without the use of verbal communication. Also, it seems odd for communication to follow a verbal track rather than the already highly developed visual one in terms of tool-making instruction. However, we can gather primates, particularly our closest relatives to be social by nature. Upon that presumption, if we then posit the Aquatic Hypothesis, it then follows that the exigencies of locomotion in water would prevent effective visual, tactile, or olfactory communication and facilitate a need to develop a vocal form. Unequivocally, other aquatic mammals have displayed a convergent evolution to harbor vocal capabilities. Namely, dolphins, whales, and the Ross Seal all have been documented to use vocal communication and echolocation under water.
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