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Original Skin. Maryrose Cuskelly
Читать онлайн.Название Original Skin
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isbn 9781582438856
Автор произведения Maryrose Cuskelly
Жанр Биология
Издательство Ingram
An article published in the Scotsman newspaper in early 2004 quoted a Scottish national survey that found that the majority of Scots were more likely to accept someone with dark skin and a Scottish accent as being Scottish than they were of accepting someone from England who had settled permanently in Scotland as being Scottish. The oldest enmities obviously die hardest.
From the earliest times, differing skin colour has been viewed as a problem with no obvious solution. When Europeans first began encountering those with darker-hued skin than their own, various theories were put forward to account for humans coming in different colours. Of equal interest to them was what could be inferred about a person from the darkness or paleness of their skin. Of course, there was a vested interest in defining non-Europeans as lesser beings than Europeans. Predictably racist theories, taking the view that the darker-skinned races were less evolved than the white man, gained support and extended to the hypothesis that those races were a different (and inferior) species altogether.
With the Enlightenment and the elevation of science that it brought, these views of the races, and their inherent differences, were supported by ‘scientific’ theories and evidence that persisted into the 20th century. In 1927, in his pamphlet titled ‘The Characters of the Human Skin in Their Relations to Questions of Race and Health’, H. J. Fleure, a professor of geography and anthropology at the University College of Wales, acknowledged the common ancestry of the world’s peoples, but took great pains to explain the different characteristics of the races. His view was that it was the superiority of the European environment that accounted for the more ‘agile brain of the European’. By contrast, the ‘specialization of both Mongolian and Negro’ skin, limiting ‘the multiplication of sensory endings’, allowed for their survival in the sweltering climate of the tropics and was responsible for their ‘lesser general irritability’ and ‘greater equanimity of temperament’.
Because Europeans lacked these adaptations of the skin, Fleure lectured on the unsuitability of tropical climates for the European. He suggested the compromise of a ‘sheltered life’ for those daring or foolhardy enough to venture to the ‘torrid’ regions and encouraged the ‘employment of coloured native field-labour’. Naturally, he warned, the ‘social dangers’ of such an arrangement should not be underestimated.
How could any reasonable person possibly take offence at these carefully constructed arguments? Such a flurry of pseudoscientific claims dressed up in ‘rational’ language carefully avoids any blatantly crude racist rhetoric. Dispiritingly, equally racist views are expressed in less rational terms on the websites of White Pride and similar organisations today.
THE REASONS for different races exhibiting different skin tones is still of interest to scientists and anthropologists. They seek to understand why such variation has developed between various populations in different latitudes of the globe. With poignant and yet naive simplicity, some even preface or append their theories with the hope that, by reducing skin colour to a response to environmental conditions, racism will somehow become a thing of the past.
The colour of human skin is mainly determined by the amount and size of the melanin molecules found within it. Layers of fat and the presence of blood vessels also play a part. Melanin is a pigment produced by cells called melanocytes, which are present in the inner layers of the epidermis. Sunlight stimulates the production of melanin, which is why skin tans when it is exposed to the sun.
Scientists, anthropologists, and casual observers alike have noted that, historically, darker-skinned peoples were found in latitudes close to the equator. An obvious and convenient explanation was that humans living in these latitudes developed dark skin as a protective device against skin cancer and melanoma, both of which may be caused by exposure to ultraviolet, or UV, light found in greater quantities in equatorial regions. While this theory has its merits, as melanin does act as a sunscreen, on its own it doesn’t account for those dark-skinned populations who went north gradually losing colour. If the likelihood of developing skin cancer were the only factor in determining concentrations of melanin in a population, it wouldn’t necessarily be detrimental to have darker skin in an area with lower levels of UV radiation. Other factors must have been at play.
Recent research into the colour of human skin begins with the assumption that our earliest common ancestors’ skin was fair. This assumption is partly based on the fact that our nearest relatives in terms of species, chimpanzees, have light skin. At birth, young chimps have pink skin on their faces, the palms of their hands, and the soles of their feet. As they age, their skin freckles and darkens due to exposure to the sun.
It is widely believed that as our ancestors moved out of the jungles and onto the sun-exposed savannah and began walking and running long distances, the issue of over-heating became more pressing. Gradually, as these creatures evolved to become modern-day humans, they became less hairy, with an increased number of sweat glands to allow them to more easily regulate their body temperature in that harsher climate. Long, thick hair remained on their heads as protection against their brains overheating. However, with the loss of body hair, their skins were much more exposed to the sun and the risks that it brings.
This leads neatly to the theory that our earliest light-skinned ancestors gradually evolved to have dark skin as a protection against sun cancer.
For American anthropologist Nina Jablonski and her husband, George Chaplin, a geographic information-systems specialist, the sun—cancer theory didn’t go far enough in explaining variations in skin colour. Jablonski believed that, as most sun cancers occur in people after their childbearing years, the impact on reproductive success, and therefore on evolution, would be minor. This point was crucial in her search to find other factors that would explain the prevalence of dark-skinned populations closer to the equator and fairer-skinned populations in the north.
Since the 1960s, scientists have known that UV light converts cholesterol in the skin into vitamin D. They have also known that melanin inhibits vitamin D production in the skin, and so that lighter skin allows for greater absorption of UV light for vitamin D conversion than darker skin does. Vitamin D is essential for the absorption of calcium, which, as practically every Australian school child could tell you, is essential for strong, healthy bones and teeth. People with calcium deficiency run the risk of developing diseases such as rickets and osteoporosis. Rickets mainly affects the young, as their skeletons are developing, resulting in soft or deformed bones. Osteoporosis, a risk in later years, results in brittle bones.
While vitamin D is available from some foods, including fish oil, most of us get the bulk of our requirements indirectly from sunlight, which carries UV light to our skin. Although rickets is relatively rare in Australia, in 2001, the Medical Journal of Australia identified a new high-risk group for vitamin D deficiency: dark-skinned women and women who wear traditional Islamic dress.
These women, because of the role that melanin plays in inhibiting vitamin D production in the skin, and because most clothing absorbs ultraviolet B radiation (necessary for producing vitamin D), are susceptible to this deficiency, and so, too, are their children.
Jablonski was able, through access to a NASA database of measurements of UV radiation at the earth’s surface, to establish that the middle latitudes do in fact get more UV light. Here, where historically people have dark skin, there is sufficient UV to synthesise vitamin D all year round. In subtropical and temperate regions, where people with lighter skin but with the ability to tan are historically found, all but one month of the year provided enough sunlight to synthesise vitamin D; and in the third region, near the poles, on average, there is insufficient UV radiation to produce vitamin D in the skin.
From another study, Jablonksi came across a crucial link between successful reproduction and skin colour. This study showed that folate, a substance necessary to prevent neural-tube defects like spina bifida occurring in developing foetuses, is depleted in the human body when it is exposed to sunlight.