29 March 2010

What skin colour means

Skin colour and race have developed loaded meanings. But when a biological explanation is given for these historical labels, people can start moving away from misunderstandings.


Skin colour and race have developed loaded meanings. But when a biological explanation is given for these historical labels, people can start moving away from many misunderstandings. ELSABÉ BRITS spoke to Prof Nina Jablonski, an international expert in the evolution of skin colour.

South Africa, in particular, carries a heavy burden of labels attached to race and skin colour. According to Prof Nina Jablonski, head of anthropology at Pennsylvania State University, the challenge today is to recognise the folly of labelling.

Jablonski is an internationally renowned anthropologist and evolutionary biologist in the study of human and non-human primates' adaptation to the environment. The focus of her study is the evolution of skin and skin colour. She was in SA to receive an honorary doctorate in philosophy from the University of Stellenbosch.

"Humans are visual organisms; everything we see, we label – including each other. We gave people labels according to their skin colour… Colour became an indicator for fundamental human qualities,” she said.

The fundamental misunderstandings lies in confusing race with skin colour.

"Skin colour is part of the construction of race, but it is not absolute – it has developed independently and various times in human history due to natural selection.

"Race is an ugly thing – it is historical baggage that has linked human qualities to it."

She is of the opinion that people have difficulty differentiating between the two because they don't want to accept evolution as fact. Skin colour is the most visible product of evolution in the human body caused by natural selection. Therefore one cannot understand skin colour and all its intrigues without a basic knowledge of evolution.

Race and God

"Some people believe God created us as specific races. That is where we get stuck. It is a very powerful rhetoric; and when human injustices are committed in the name of God, or in anyone's name, we have to stand up and say so.

It is ironic that in South Africa, with one of the world richest fossil sources, opposition to the concept of evolution persists – as in America. Science shows us, however, that the genetic differences between people “are minimal, a fraction”, says Jablonski.

"South Africans must embrace the evolutionary biodiversity and take another look at the labels of the past. For me, South Africa is the spring water of the human race. With its diversity it offers so many possibilities.”

The origin of skin colour

Humans and their closest living relatives, chimpanzees, were separated from their common ancestor around 6-million years ago, with each strain developing in different branches. This common ancestor was covered with dark hair with light skin underneath. Around 4-million years later, or 2-million years ago, Homo erectus, also called Homo ergaster, migrated out of Africa.

By now, this ancestor had a larger brain, which had certain biological implications: the body has to work harder to keep the brain cool. Although H. erectus was not the first hominid to walk upright, he walked faster and further, which also required cooling. To sweat properly requires many sweat glands and a naked body.

By 1,6 million years ago, human ancestors had a dark skin with considerably less hair, and by around 1 million years ago, the skin was almost naked. So the loss of hair was an important part of becoming human, like the fact that we learned to make fire, walk upright and hunt.

Naked skin is susceptible to harmful ultraviolet (UV) rays, so melanin – our natural sunblock - developed. A skin that darkened, but which allows just enough UV rays through for the body to produce vitamin D, was therefore essential for survival.

And that’s how we arrive at Homo sapiens, 200,000 years ago in East Africa, close to the equator, with a dark and relatively hairless skin.

Migrations of H. sapiens out of Africa began 80,000 years to Australasia, 65,000 years ago to East Asia, and 45,000 years ago to Europe. In areas where UV rays are considerably less, our ancestors had to lose the protective melanin pigment in the skin in order to let the Vitamin D production continue. That is how people those migrants developed lighter skins.

According to Jablonski, the depigmentation of skin colour developed independently in the ancestors of Europeans and Asians, and there are independent mutations in the human genome for depigmentation of melanin (lighter skin).

Also, in countries such as India and Pakistan, people became darker in a process known as repigmentation, because they returned to a tropical climate. "Natural selection happened in different parts of the world in the same way because circumstances were similar. The development of skin colour was not random, but is linked to migration patterns and the sun."

(Edited extract of a feature originally published in Die Burger, Health24, March 2010)


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Skin expert

Dr Suretha Kannenberg holds a degree in Medicine and a Masters in Dermatology from the University of Stellenbosch. She is employed as a consultant dermatologist by Stellenbosch University and Tygerberg Academic Hospital, where she is involved in clinical duties and the training of medical students and dermatology residents. Her areas of interest and research include vitiligo, eczema and acne. She also performs limited private practice work in the Northern suburbs of Cape Town in general and cosmetic dermatology.

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