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Re: A large cranium isn't the only... *LINK*

The Scars of Evolution by Elaine Morgan
Chapter 5: The cost of a naked skin:

“There are one hundred and ninety-three living species of monkeys and apes. One hundred and ninety-two of them are covered with hair. The exception is the naked ape self-named Homo sapiens. The zoologist now has to start making comparisons. Where else is nudity at a premium?” Desmond Morris

Darwin, as we have seen, believed he could accommodate human bipedalism within the basic framework of his theory. He thought it possible that walking upright made our ancestors fitter to survive. But human nakedness was a different matter. He had no illusions about that. In his book on the Origin of Species, published in 1859, he gave copious examples of how natural selection worked, but he did not discuss the human species in relation to it. After stating his belief that his theory would open the way to new avenues of future research, he contented himself with thirteen words on Homo sapiens. ‘Much light,’ he wrote, ‘will be thrown on the origin of man and his history.’

This reticence is sometimes ascribed to prudence, or caution, a desire to minimise the hostility he knew he was going to encounter. If that was his hope it was certainly not fulfilled, and he cannot seriously have expected it to be. In the famous Oxford debate of 1860, all the most heated arguments raged not around the theory in general, but around the one omitted topic – man’s relationship with the apes. There could have been a different reason for the omission. Perhaps he was not ready to give an account of human evolution while there were things about it he could not understand. He could not, for example, convince himself that being naked could possibly make a primate fitter to survive. This is what he had to say about it:

“The loss of hair is an inconvenience and probably an injury to man, for he is thus exposed to the scorching of the sun and to the sudden chills, especially due to wet weather. No one supposes that the nakedness of the skin is any direct advantage to man; his body therefore cannot have been divested of hair through natural selection.”

The most striking thing about the statement is that most modern evolutionists – some of them more Darwinist than Darwin himself – would find it impossible to accept. They start with the axiom that man evolved on the savannah, they observe that he has lost his body hair, and they conclude that nakedness must, therefore, have been an efficient adaptation for life in that milieu.

Practically all the contemporary theories about nakedness begin with the concept of a torrid savannah and an overheated ape. That is an oversimplified picture of a savannah environment. It is perfectly true that the days are hot there, sometimes very hot; but in the nights the temperature can sometimes drop as low as 11°C, and the indigenous animals have to live there for twenty-four hours a day.

In 1989 the BBC sent a series of outside broadcast crews to spend an entire day on the savannah, sending back live pictures of the wildlife to be slotted into the viewing programme at intervals during the day. Some magnificent shots of wildebeest, lions and elephants were obtained, but in some ways the most memorable shot was the final one of a couple of broadcasters muffled up to the eyebrows trying to keep their teeth from chattering. As one reviewer summed it up, ‘The weather broke, the light went, and Julian Pettifer nearly died of exposure.’ It would not have been a good time to explain to Mr Pettifer that his ancestors has shed their fur to make them better fitted to survive in these conditions.

If they had kept their coat of fur they would have been better insulated not only against the cold of the night but also the heat of the day. All desert animals have retained their fur. In hot countries, shaving off even a portion of wool from a sheep’s back leads to an immediate rise in its internal temperature and the rate of panting. Desert-dwelling humans like the Bedouin keep their heads and bodies covered when out in the sun, just as northern peoples cover themselves with clothes when out in the wind, in both cases attempting to replace the natural protection that our species has lost.

A covering of either fur or feathers has been standard equipment for warm-blooded creatures ever since they emerged over a hundred million years ago, and ultimately took over from the reptiles as the dominant form of animal life.

One of the many advantages of such a covering is the ability to adjust the thickness of insulation within seconds. Hairs and feathers have erectile muscles attached to them, so that robins, for instance, can puff out their feathers when the temperature drops; animals can erect their hairs either in response to cold or danger; cats and dogs bristle the hair on their backs when confronted with an enemy in order to look larger and more intimidating. Humans still retain the capillary muscles in good working order, but their functioning is comically ineffective. Since the vestigial hairs they are attached to often fail to reach the surface of the skin, the only result achieved is goose-bumps. We produce them in cold weather with the subconscious aim of bushing out a non-existent coat of fur. When we are frightened, some primitive level of our brain may try to raise our hackles in the hope of scaring off the enemy.

Hair or fur is a mammal’s first line of defence against abrasions – cuts and grazes, the sting of an insect, the scratch of a thorn. Perhaps partly in an attempt to replace this defence, our skin has become thicker than that of our nearest relatives, the apes. Yet at the same time human skin contains more blood vessels and in more richly endowed with nerve endings. This means that even a small lesion is liable to bleed more and hurt more, than if we had skin like an ape’s.

Much in the news recently is another disadvantage of nakedness – the danger to light-skinned races of over-exposure to ultra-violet light and the consequent risk of skin cancer. Most mammals do not incur this risk, except where the hair is missing. In horses, for example, a malignant melanoma may sometimes develop in a bare patch under the tail.

Cancer is the most serious of the possible ill-effects of exposure to ultra-violet rays, but it is not the only one. Exposure to strong sunlight can damage light-coloured skin to the extent of putting the skin glands temporarily out of action. In the heyday of the British Empire, young men and women fresh out of England to serve in India found that part of the white man’s burden was susceptibility to an uncomfortable skin condition known as ‘prickly heat.’

Since the loss of body hair, human skin has elaborated an auxiliary line of defence against the danger of ultra-violet rays. Scattered throughout the top layer of our skin are small spider-shaped cells (melanocytes) which produce a substance called melanin, after the Greek word for ‘black.’ The cells respond to ultra-violet exposure by increasing the output of melanin, which is injected into the surrounding skin cells where it forms a protective shield like a minuscule sunshade over each cell membrane on the side nearest to the surface. This darkens the colour of the skin and protects it by absorbing the harmful ultra-violet rays. In the dark-skinned races the protective shield is permanent.

There is some melanin in the skin of apes and monkeys, but its purpose there is more obscure. It is hardly needed as a protection against the sun, for most of these animals live in shady places, and all of them have bodies which are covered with hair. Since their skin colour thus cannot affect their chances of survival, it is not governed by the influence of natural selection, and varies widely between species, and sometimes between individuals. The Celebes ape is born with a black skin which later turns white. The rhesus monkey’s skin is pinkish with random splotches of blue. There may be dark-skinned and light-skinned individuals within a single troop of chimpanzees.

In the days when Theology was queen of the sciences learned men were as curious about their progenitors as we are today. One of the questions they asked themselves was ‘what colour was Adam?’ Considering in whose image Adam was created, it was a matter of some delicacy, never satisfactorily resolved. The old monks who had the job of illuminating Holy Writ ignored the issue, and went on drawing little pictures of a white Eve with a white Adam.

Some of the early evolutionists thought they had cracked the problem. Since they could now dispense with Adam, they felt able to jettison the egalitarian Biblical doctrine that all men were brothers; they suggested that the races had always been separate, having evolved independently from the beginning. Behind that hypothesis we seemed to detect an unspoken conviction that some of us are obviously descended from a rather better class of ape than others.

We now know that all races share a common ancestry, and there is every reason to believe that our earliest common ancestors lived in Africa, where protection against ultra-violet rays would have been at a premium.

This conclusion had been challenged. It is argued that protective pigment could not have evolved by natural selection because the danger it protects against does not usually manifest itself until middle age, when child-bearing is over; therefore, a female who was not protected against skin cancer would produce just as many offspring as a protected one, and her genes would not be selected out. This argument is unsound. Half our genes come from our fathers, and a man’s reproductive capacity does not close down as early as a woman’s. He can certainly increase the number of his descendents by avoiding late-onset disease and living longer, so that over time natural selection in an African climate would favour dark skin.

Besides, the white races bear evidence of ancestral pigmentation in their own skins. All human beings, of whatever race, have the same number of melanocytes. In northern races they are largely surplus to requirements and remain relatively inactive because in temperate climes the ultra-violet rays are seldom strong enough to be dangerous. But they are still there, presumably a relic of our heritage.

So the question of racial differences in skin colour does not revolve around the question of why some human populations became black, but why some later faded to lighter shades. The best available theory is that it happened when they migrated from Africa to northern latitudes where the climate was cooler and cloudier and where the food was scarce in winter.

They were then in less danger from the strong sunlight and in more danger from lack of vitamin D. A shortage of this vitamin in the diet does not matter too much in hot countries. Cells in the skin can manufacture their own supply, but they cannot do it – any more than a leaf can manufacture chlorophyll – in the absence of sunlight. The best survivors in northern countries would be the ones with the least active melanocytes (that is, the palest skin) because the limited available sunlight could soak into their skin more easily and help make vitamin D.
So it could be claimed that in the end natural selection did a good job, under difficult circumstances, both for the dark races and the pale ones. As a method of counteracting part of the ill-effects of hair loss, it was indeed a neat piece of damage limitation. The drawback is that it takes a very long time for human population to evolve the kind of skin colour fitted to particular latitude. The system is foolproof only as long as people stay put, and sometimes they suffer from it.

For example, when Asian women settle in Britain and continue to live on the same diet that kept them healthy in India, they are sometimes found to be suffering from rickets. A tropical sun is strong enough to penetrate through a thin sari and enable their skin to make vitamin D, but the British climate leaves them deficient in it. The reverse move – from the temperate zones to tropical ones – can be even more damaging. People of European origin have made their homes in all parts of the world and the possible ill-effects have only recently been fully appreciated. There has been a startling increase in the frequency with which malignant melanoma occurs throughout the Western world, with a doubling of the frequency of the disease each decade since records started. The rise has been highest among white populations living in hot countries, and Celtic races seem to be especially vulnerable.

It is very rare in dark-skinned people, and the incidence among the whites seems to vary with the distance from the equator. It is high in places like Arizona, Israel, Hawaii and Australia. In New South Wales it accounts for seven per cent of all cancers, as compared with one per cent in the United Kingdom. There are now fears that damage to the ozone layer could accelerate the increase.

‘Naked as Nature intended’ was a persuasive slogan of the early Naturist movement. But Nature’s original intention was that the skin of all primates should be un-naked. Faced with the phenomenon of the bald-bodied ape, she has tried various experiments, without finding a universal solution. Doctors have tried to publicise the fact that exposure to sun is possibly dangerous; and in the long run anti-cosmetic – it is the direct cause of the wrinkles associated with ageing and the broken veins which sometimes appear under the skin. But their campaign has had only limited success. In an American survey, over 50% of those questioned knew that there was a link between sun-bathing and cancer, but two-thirds of that number continued to sun-bathe and in most cases without using a barrier cream. Westerners cling to their belief that a tanned skin is ‘healthier’ than a pale one, and to even more insidious idea inculcated by Coco Channel that a tanned-skin should be regarded as fashionable, and sexy, and a status symbol.

Some of the physical left-overs from a previous hairier existence remain with us (like the goose pimples), doing neither good nor harm, and in the long run will probably disappear. A more mysterious phenomenon is that of the sebaceous glands which cause anguish to so many adolescents by being the cause of greasy skin and acne. The oiliness comes from the fatty substance called sebum. The sebaceous glands which secrete it are an appendage of the hair follicles, and the sebum seeps out onto the hair shaft and helps to keep the fur of mammals sleek and waterproof. A. M. Kligman, who made a special study of the subject, wrote:

“The original purpose was not so much to protect the skin as the hair. In man, however, save for a few specialized regions, hair is a vestigial and rudimentary feature. With hair rendered obsolete, the sebaceous gland is literally out of work. It is a living fossil with a past but no future.”

So it would be reasonable to expect that in man the glands would have dwindled to mere vestiges, just as over most of our bodies the hairs themselves have dwindled. Instead of that, these oil glands have run riot. In our nearest relatives, the African apes, some sebaceous glands are found scattered over the body, but they are few and small. In man they are numerous and relatively enormous, especially on the face and scalp, sometimes extending to the neck and to regions of the upper part of the body. An American enquiry into “What good is human sebum?” reported that the short answer was ‘No good.” It is not needed to keep the skin moist and supple: the softest human is that of a child, yet the sebaceous glands do not begin to operate until puberty. It used to be thought that the sebum probably helped to kill bacteria which landed on the skin, but that proved to be a fallacy. Yet from adolescence onwards our skin goes on producing sebum, not in response to any environmental stimulus (as is the case with sweat) but as a constant rate.

Globules of fat emerge from the sebaceous glands onto the surface of the skin, mingled with dead and decaying fragments of cells. The mixture is toxic to living tissue. At puberty the glands are growing so rapidly in the so-called ‘acne areas’ (face, chest and back of the torso) that the well of the hair follicle may become filled with a plug of sebum and cell debris. Or a cyst may be formed in which trapped bacilli produce irritant fatty acids and cause inflammation. The clinical symptom – pimples, black-heads and inflamed nodules – are found most often on the face, but may extend to all the acne areas. On the scalp, where the follicles are less likely to become blocked, the same generous effusion of sebum provides a breeding ground for seborrheic dermatitis, otherwise known as dandruff.

The unmerited disaster may be visited on young people of either sex, but there are more victims among young males because males have larger sebaceous glands. The size of the sebaceous glands is influenced by the sex hormones (castrated males do not suffer from acne), and attempting to tinker with the balance of these hormones can have side-effects more dismaying than pimples. The effects may be partly mitigated by use of antibiotics, but the only permanent cure is to grow older. With the passage of time the skin gradually adjusts to the situation, and the sebum is able to make its exit to the surface without battling its way out. After that the cosmetic results are less noticeable. Often they are confined to what the face powder advertisements used to denounce as ‘shiny nose.’

It is cold comfort to a fifteen-year-old to know that the condition will not last, or to reflect that no other species in the animal kingdom has to put up with it. William Montagna, leading specialist on primate skin, commented: “The human body appears to contain senseless appendages and even to make mistakes, but the sebaceous glands are too numerous and too active to be described as trivial.”

Other equally unexpected features of human skin remain to be discussed, but one thing should already be clear: a mammal cannot shed its coat of fur as a man can shed a suit of clothes and leave everything else unchanged. It is as revolutionary a change in life strategy as walking on two legs, and as far- reaching in its secondary effects. These complex changes would not have evolved, in our species alone, without compelling reason." TO BE CONTINUED

Messages In This Thread

Oldest "Human" Skeleton Found... *LINK*
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Re: Oldest "Human" Skeleton Found... *LINK*
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Is the 'elephant ' finally in sight? *LINK*
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A large cranium isn't the only... *LINK*
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You tell me... *LINK*
How about this choice? *LINK*
Re: A large cranium isn't the only...
Re: A large cranium isn't the only...
Re: A large cranium isn't the only... *LINK*
Asked and Answered *LINK*
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Archaic humans such as Neanderthals... *LINK*
Re: Archaic humans such as Neanderthals... *LINK*
Re: Archaic humans such as Neanderthals... *LINK*
Lost Civilization May Have Existed Beneath... *LINK*
Re: Lost Civilization May Have Existed Beneath... *LINK*
The Gorillas are killing us! *LINK*
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Re: The Gorillas are killing us! *LINK*
Re: The Gorillas are killing us! *LINK*
Re: The Gorillas are killing us! *LINK*
Re: The Gorillas are killing us! *NM* *LINK*
Re: The Gorillas are killing us! *LINK*
Re: The Gorillas are killing us! *LINK*
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Re: A large cranium isn't the only... *LINK*
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Re: A large cranium isn't the only... *LINK*
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Re: A large cranium isn't the only... *LINK*
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