South Africa is probably the most appropriate place on Earth for Nina Jablonski to address an audience. You could practically hear the preconceptions of her largely white, largely older audience being re-wired while she spoke at an open lecture at UCT’s Medical Faculty on Wednesday night. Jablonski, who is more often found at Pennsylvania State University, was in town to give one of the African Genome Education Institute’s Darwin Seminars.

Jablonski, who is technically a primatologist, an anthropologist, palaeontologist and evolutionary biologist, is nuts about skin. A few years ago she told the New York Times that her preoccupation began while she was teaching anatomy to medical students in Hong Kong in 1981. She noticed that when the students were presented with a cadaver to dissect, they were scared and freaked out. But once the skin had been pared away, they were able to view the body far more neutrally and proceed with the task at hand. 

“That moment showed me how much of what we consider our humanity is imbued in our skin,” she told the newspaper. “It stayed with me for a long time.”

Jablonski began studying the history and evolution of skin colour – no easy feat, because fossil records contain no traces of skin. Though the current variations of skin pigmentation have been abundantly recorded, compared and geographically mapped, there has been little discussion of why human skin tone had evolved in such a way that we find some of the darkest skin pigments in Africa and some of the lightest in Northern Europe.

Without fossils to fall back on, she turned to our closest relatives, chimps. (Jablonski made headlines in 2004 when she discovered the world’s oldest chimpanzee fossil, at half a million years old.) Although chimps are covered with a thick matt of dark hair, underneath that they have fairly lightly pigmented skin: infant chimps in particular have very light skin because it has not yet begun to be darkened by UV radiation. 

Jablonski displayed a picture of the skeleton of Lucy, the 3,2-million-year-old Australopithecus specimen discovered in Ethiopia in 1974. Although Lucy had the ability to walk on two legs, it’s believed that her lifestyle was more ape-like than human – she would have spent more time climbing trees, for instance, than running in the sun. Because she didn’t do much running, she wouldn’t have had to keep her body and brain cool through sweating, so Lucy, too, would have been likely covered with dark fur. It was when the earliest humans developed long limbs suitable for running that they lost their hair, in order to facilitate the evaporation of sweat. Naked skin became de rigueur for humans between 1,5 and 2 million years ago.

Without their protective hair, Jablonski surmises, the earliest humans – based in Africa – would have evolved permanently dark pigmentation. The reasons for this have everything to do with UV radiation, levels of which are highest over dry areas around the Equator. “In evolutionary terms, what has evolved in human skin is a permanent natural sunscreen,” Jablonski explained. Dark skin contains high quantities of “eumelanin”, a dark pigment which has the ability to absorb and scatter UV radiation. People with dark skin, then, can absorb tremendous amounts of UV radiation.

That explains why the first humans had dark skin. But how did the lighter shades come about? The answer lies in migratory patterns. Jablonski reports that the fossil record indicates that homo sapiens dispersed energetically from Africa, with the first waves of migration taking place about 100,000 years ago to the Mediterranean, followed by the Indian subcontinent and Asia. Migration to Western Europe happened relatively late – only 40,000 years ago. The humans who left the mother continent underwent interesting evolutions in their pigmentation.

The Northern Hemisphere, as anyone who’s ever spent a winter in the UK will know, is very UV-poor. In particular, no UV-B rays make it through to the Northern Hemisphere in the height of winter, which is what is necessary for the skin to start the vital process of making Vitamin D. (Vitamin D is essential because it maintains the immune system, ensures bone growth and inhibits cancer.) The original homo sapiens who flocked to this UV-depleted region would have suffered serious health problems as a result of the slowed vitamin D production in their skin, which led to a process of “depigmentation” – skin getting lighter – in order to absorb as much UV into the skin as possible.

(Even then, Jablonski notes, the only way that humans could evolve to live above the latitude roughly on which London falls – due to the paucity of UV – was to become proficient at catching and eating Vitamin D-rich foods: oily fish and marine mammals.)

“Skin pigmentation is an evolutionary compromise,” Jablonski said. At the equator, what you need is maximum sunscreen. Closer to the poles, what you need is maximum photosynthesis ability. Moderately pigmented people evolved in moderate climes. 

Of course, modern humans live far from their ancestral homelands, and have done – whether voluntarily or not – ever since the advent of long-distance mass transportation. Also, as Jablonski put it: “Lucy did not go on holiday” – a point which she illustrated with a slide of the stereotypical Englishman at the beach with a terrible sunburn. What is common to most people in big cities these days, she says, is that they work indoors all day – which is why Vitamin D production is becoming a problem once more, particularly when concealing clothing is worn. To illustrate this, she points to the high prevalence of osteoporosis in Muslim women who wear full hijab. 

But the real crux of this all, Jablonski says, is the point that skin pigmentation evolved independently of other physical traits, and not in tandem with a bucket of the other physical characteristics commonly used to distinguish race. “So we cannot group people into genetically distinct groups based on skin colour,” Jablonski holds. “Skin pigmentation is not a unique attribute that can be used to define human races.”

History tells us that, nonetheless, this is exactly what has been done. When Swedish zoologist Carl Linnaeus was drawing up his classifications of animals and plants in 1748, he grouped humans together only by continent and colour. Ten years later, however, he expanded his classification of humans to define the groups not just by geography and skin tone, but also by character, disposition and morality. 

He based his classification in this regard on the ancient theory of the “Four Temperaments”, which held that there were four essential bodily fluids that affected human personality. So in terms of Linnaeus’s 1758 revision, Africans became “phlegmatic”, for instance, and the Europeans “sanguine”. 

However, Jablonski notes, Linnaeus stopped short of explicitly suggesting that there was any kind of race hierarchy attached to these classifications. Later scholars jumped on his taxonomy with alacrity and did just that. The 18th century German philosopher Immanuel Kant argued in Of the Different Human Races that each race had fixed, immutable qualities, and he placed them in a hierarchy. “The yellow Indians do have a meagre talent,” he wrote. “The Negroes are far below them, and at the lowest point are a part of the American people.”

These racial definitions and stereotypes became what Jablonski terms “colour memes”, endlessly reproduced and given weight by being promulgated by well-respected scientists and philosophers. The legacy of this racist typology is, as no South African needs to be told, still with us today. 

“Skin colour is the most visible product of evolution – use it as a teaching tool,” Jablonski urged the audience on Wednesday in conclusion. “Now that you’ve learnt that there’s no relationship between skin tone and race, take it forward to help promote the end of racism and race-based discrimination.” DM

Read more:

• Always Revealing, Human Skin Is an Anthropologist’s Map, in the NY Times

Photo: Nina Jablonski delivers the African Genome Education Institute’s Darwin seminar (Daily Maverick)