evolutionary biology and medical reasons to be.
The ‘dark is beautiful’ campaign I have seen in the Indian media is excellent advice on both the social and medical fronts. I say this as someone who, in addition to being trained in family medicine and plastic surgery, is a skin cancer specialist, and designs and develops cosmetics as well.
What makes us have different skin colours is a rather inert pigment called melanin. Strangely, however, all skin types have the same number of melanocytes or cells containing melanin - 10,000 cells per square cm. So why do we have different skin colours?
In my recently released book, Skin: A Biography, I talk about the evolution of skin colour. Essentially, changes in skin colour came about in two ways, the first time, through an evolutionary response, and then, through an adaptive response.
All human beings developed from apes. The first of the apes evolved around 28 million years ago, while the first humans evolved around 100,000 years ago, in Africa. And, essentially, skin colour initially evolved as a battle between two vitamins, folic acid (folate) and vitamin D.
How did this happen? The process took hundreds of thousands of years. As apes became more active and started walking more upright, their bodies started overheating. To balance this, they began shedding hair to become ‘naked apes’, aka primitive man.
However, with this change came a concurrent need to preserve the folic acid in our bodies. Folic acid is essential for reproduction and its lack leads to birth defects like spina bifida. Sunlight destroys folic acid, and to prevent this, the skin of the naked ape darkened from pink to black. This is because the darker the skin, the less transparent it is, and the less sunlight it absorbs.
This is how African skin became black – in an evolutionary process to preserve folic acid. And folic acid’s relationship with reproduction and prevention of birth defects is also the reason darker-skinned races, such as those in Asia and Africa, generally have larger populations and fewer birth defects (taking into account less medical intervention).
However, the advantage that darker skin had to preserve folic acid came with a corresponding disadvantage. By keeping out more sunlight, dark skin reduced the body’s capacity to synthesize Vitamin D. Vitamin D is essential for our bodies to absorb the calcium and phosphate we get in our diets, and which we need to keep our bones strong.
As modern man migrated out of Africa 100,000 years ago into Europe, the darker-skinned people over a period of time began to develop rickets, as the skin was not light enough to absorb vitamin D. Some parts of Europe close to the North Pole didn’t see the sun for 6 months!
Rickets is a double whammy in the evolutionary sweepstakes, because not only does it make one infertile but also makes one deformed. The former breeds you out by natural selection; the latter makes you less likely to be chosen in a sexual selection process in which mating partners are chosen.
Therefore with time, dark skin grew lighter in Europe. The fact that the darker skins became associated with disease (the rickets caused by the lack of vitamin D) may have started the initial misconception that white skin was superior overall. In fact, it is superior, but only in an environment where there was less sunlight. (Diet also plays a part in skin color changes, but this is a story I shall save for another day).
However, the story doesn’t end here. There was another migration of man 50,000 years ago – these men and women walked across shallow seas and land, and reached areas like the Andaman Islands, Philippines and Australia.
Even more ‘recently’ - within the last 5,000 years – people with the European skin types migrated across the Indus Valley into India and southern Asia. The skin of these migrants again darkened over the next 2,000 to 4,000 years.
This was an adaptive response to the tropical sun, and not an evolutionary response as happened over millions of years in Africa. Again, this happened to protect folic acid levels in the body, as white skin was not conducive to promoting breeding in tropical climes, since light could penetrate it easily. Darker skin also helped to prevent diseases like skin cancer.
However, brown skin brings with it the vitamin D problem. It’s a simple problem, which sunlight can fix. But South Asians avoid exposure to the sun to avoid tanning or darkening of skin. Given their existing predisposition to having low vitamin D levels, virtually the entire population is vitamin D deficient.
In fact, this was one of the reasons that triggered my interest in the evolutionary ‘biography’ of skin and skin colour. Several years ago a young woman in her 30s came to see me. She and her husband had been trying for years to conceive and her IVF procedures had been unsuccessful. Someone had suggested that she consult me. Since she was brown-skinned like me, I arranged for her vitamin D levels to be checked. They were extremely low.
One of the things sometimes forgotten by fertility clinics is the effect of vitamin D on fertility or reproductive hormones. Checks are usually done for all other reproductive hormone levels, but not always for vitamin D.
Vitamin D affects functions of the reproductive system in both men and women. In men, it causes lowered testosterone, and in women, it has the opposite effect – raised LH/FSH hormone levels – which are implicated in polycystic ovarian disease and also infertility. Even when those hormone imbalances are corrected, it is important to make sure vitamin D levels are normal.
In this case, I prescribed 50,000 I.U of vitamin D per month. At their next attempt at IVF, the couple successfully conceived, and were delighted with the outcome. Fortunately I managed to talk them out of naming their child after me!
More recently I saw a young baby who had recurrent ‘coughs and colds’ and was given no other diagnoses when he was admitted to the hospital for various tests. The paediatricians just diagnosed him with ‘failure to thrive’ as he was beginning to plateau in his height-weight chart. They had not specifically tested for vitamin D, as he had clinically normal bones and teeth.
I asked for a check on vitamin D levels. The levels were non-existent. The child had been exclusively breast-fed as the mother knew from the media that ‘breast was best’. However, breast milk lacks vitamin D.
Often, in modern medicine, we don’t think of historical illnesses like rickets and how relevant they might be even today in our understanding of how our bodies work and why. I myself have been caught out by not thinking of rickets in another ‘failure to thrive’ case. Once. Earlier.
To further understand the difference between the health impacts of evolutionary versus adaptive darkening of skin, try testing Africans from the original tribes in Tanzania. While they may be much darker-skinned than people with some Indian skin types, they nevertheless seem to have twice as much Vitamin D, especially pre-Vitamin D, as Europeans, and four times as much as those with South Asian skin.
Today, in Australasia, where most of the population is from the British Isles, we have the highest skin cancer rate in the world. In time, white skin here will gradually ‘brown up’ as skin did in India – but this process takes more than 3,000 years and will not be in our lifetimes. Evolutionary biology is also why African ‘skin’, since this was the first to evolve and had millions of years to develop high pre-Vitamin D level, is naturally more athletic – Vitamin D helps develop muscle strength, size and also aids faster recovery from injury).
As I say in my book:
“There were good reasons for dark skin in Africa, but in European climes they just did not make sense. It was a battle between two vitamins, and skin ended up becoming the final arbiter.”
And all things considered, brown skin is the most ‘sensible’ skin type nature could have created for our climate. The evolutionary process is all about propagation of the species and it doesn’t care about beauty or skin cancer – the former is fleeting and doesn’t last; the latter generally occurs after our reproductive peak.
So to get back to beauty creams, ‘fair’ and ‘dark’ skin, and our obsession with getting, or not getting, tanned.
We can use skin creams that have some sun protection built in, to reduce the effects of tanning. We may even use some ‘whitening’ creams, which are specifically designed to reduce uneven pigmentation – an issue in South Asian skin types because we have more pigment in our skin. But fairness creams are a myth, and a waste of time – as real changes in skin colour will take longer than our lifetimes.
Dr Sharad Paul is the author of Skin: A Biography. He was a finalist in New Zealander of The Year, 2012. He won the Chair’s award from the New Zealand Medical Association, 2012. Read him on www.sharadpaul.com. Follow him on https://twitter.com/drsharadpaul