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03 Jul 1998 00:00
Racial differences between people may be a more recent phenomenon than was previously believed. In a paper presented to the Dual Congress of Human Biology and Palaeontology at Sun City this week, renowned academic Dr Christopher Stringer suggested that white skin colour probably emerged only 30 000 years ago.
This is some 30 000 to 50 000 years more recent than has been scientifically accepted.
Stringer, the man behind the “Out of Africa” theory of human evolution, believes humankind’s original skin colour was dark.
He says white skin pigmentation evolved in response to northern hemisphere climates after Africans migrated to Europe.
He is supported by Professor Trefor Jenkins of the South African Institute for Medical Research, who suggests that in several thousand years’ time our descendants may revert to being dark again.
The “Out of Africa” theory, which has gained considerable ground over the past decade, holds that Homo sapiens developed in Africa, and then between 100 000 and 60 000 years ago, spread out into the rest of the world, eventually to replace the Homo erectus populations that had left Africa around 1,5- million years ago.
This view has been supported by geneticists such as Mark Stoneking and Allan Wilson of the University of Berkley, California, who in a ground-breaking project in the late 1980s developed a DNA “molecular clock” which could measure the rate of change in human populations.
The implications of this theory are that racial differences are very shallow, given their recent development in an evolutionary line that goes back about five million years.
The “Out of Africa” theory is not without its ideological opponents.
The “Multi-Regional”, or “Assimilation”, school of thought argues that racial differences developed deeper in the distant past and that migrants were absorbed into populations elsewhere in the world rather than replacing them.
The scientific jury is still out on the issue.
Most geneticists and palaeontologists favour the “Out of Africa” view, although they have been urged to be cautious by the doyen of fossil finders, Dr Tim White. He says there are still problems with the theory and that proponents of the “molecular clock” should not invent “virtual earth histories” that have nothing to do with archaeological realities.
Nonetheless, there appears to be consensus that the early Homo sapiens was black or brown. But as Stringer points out, we’ll never know because no evidence survives in the fossil record.
Biologists argue that skin colour is a function of a relationship between protection (against harmful ultra-violet rays) and chemistry (the manufacture of vitamin D through the absorption of sunlight by the body).
Given that early humans developed in Africa where the climate was hot and the skies were clear, it stands to reason that our ancestral pigmentation was dark. Once they moved into Europe, they were confronted by the Ice Age , where sunlight was a scarce resource. Survival necessitated a more translucent skin.
So will all white South Africans one day become black?
“There could be a reversal in pigmentation in the relatively short space of a few thousand years,” says Stringer. “White Australians have the highest skin-cancer rate in the world and the same might be true for white South Africans. Left to natural selection, there could be a gradual change in skin colour, but protection is more likely to come about through the interference of modern medicines, for instance, vitamin D supplements and skin-protection cosmetics.
“What is happening, though, is that genetic evolution is continuing. The racial differences today are far less pronounced than they were a thousand years ago because of the increase in mobility of human populations. It may be that our descendants all end up as one colour one day.
“What’s probable in the shorter-term,” Stringer adds, “is that smaller groups like the Khoi San will be swamped entirely by the major racial groups that have emerged in the modern world.”
One of the topics up for discussion at Sun City has been the human genome diversity study, which aims at gathering data from ethnic minorities.
Although the project is controversial, given the complexities of race politics, its proponents believe it’s essential the human gene pool be scientifically analysed in to identify traits among fringe groups that could have a bearing on immunology. Diversity, they point out, led to the success of the human race. The lack of diversity may in the future lead to our demise.
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