As I wrote in my book, The Genetics of Health (Simon and Schuster), over the past 50,000 years we humans have speeded up evolution by expressing new genes—due to new diets and diaspora. My book essentially looks at howhumanity haggled with our individual and familial pasts to shapeour genetic blueprints, and this can determine ourpersonalpropensity to develop certain diseases. I believe such targeted therapy is the future.I believe this“RxEvolutionary” approach to healthcare is important as it allows us to practic emedicine personalized to each patient, taking into account cultural and ethnic differences. Evolutionary biology tells us that particular ethnic groups are predisposed to certain medical conditions, especially when cultural and culinary factors are added into the mix, so why not take these into account?Given I was in London for theJLF @ the British Library (an offshoot of the massively famous Jaipur Literary Festival), an event that showcases Indian literature and history, I thought I’d look at some aspectsof evolutionary biology and how they shaped the health of the Indiansubcontinent.
Firstly, all skin colours evolved due to the battle between folic acid (needed to reduce birth defects) and vitamin D (needed for skeletal muscle strength and optimal calcium metabolism). Folic acid is destroyed by light, whereas vitamin D is produced by skin on exposure to sunlight. The lighter your skin, the more your folic acid gets destroyed — and hence darker continents like Africa and Asia have large increasing populations, while northern European populations are declining. When people migrated into the Indian subcontinent from Europe, in the last 10,000 years, their skin colour darkened to preserve folic acid. This process takes several centuries—and the Indian subcontinent became darker-skinned and more populous than Europe over time.
The lighter your skin, the more your folic acid gets destroyed — and hence darker continents like Africa and Asia have large increasing populations, while northern European populations are declining.
But with the darkening of skin came the parallel problem — an inability to absorb vitamin D efficiently. Over time this would make people on the Indian sub-continent shorter in stature and less athletic than their European ancestors (1 billion people and not even 1 Olympic track and field medal?). Africans, in contrast changed their skin colour over millions of years and hence developed high pre-vitamin D levels that make them natural athletes. As I wrote in my book, The Genetics of Health (pg.154):
Later, as white-skinned people migrated east from Europe, reached the Indian subcontinent, and ventured farther south into Asia, to more tropical climates, the skin again darkened to preserve folic acid. However, this darkening came after an initial period of lightening in Europe and therefore happened over thousands of years, as recently as four thousand to ten thousand years ago. Therefore, the body did not have time to hoard pre-vitamin D, as this darkening of skin was an adaptive response to preserve folic acid under the tropical sun, not an evolutionary response as had occurred in Africa. Therefore Asians, especially those from the Indian subcontinent, have very low vitamin D levels.
But vitamin D is an imposter among vitamins, as it can be produced by our bodies. Vitamins, by definition are nutrients we don’t produce and therefore weneed to obtain them via our diets.Essentially vitamin D functions as an ancient hormone that regulates calcium metabolism. But in the context of the Indian subcontinent, the importance of vitamin D cannot be overstated.
Firstly, upper-caste Hindu Brahmans were vegetarians and over centuries their skin lightened—as their diets of vegetable, fruits and cereal had no vitamin D (when compared to diets of meat, especially fish). It became naturally more desirable to appear lighter-skinned (and thereby upper class)—and sowed the seeds for an obsession with fair skin, even before waves of European colonizers arrived. People avoid the sun like the plague in India!
Yoghurt (often referred to as “curd” in India) accompanies most meals in India. But consuming calcium (via dairy) or taking calcium supplements while being vitamin D deficient can end up problematic—as calcium, in the absence of its regulating hormone, runs amok. Vitamin D deficiency increases levels of two hormones—parathormone and calcitriol—that increase absorption of calcium from the intestines.
This leads to more calcium inside cells (intracellular calcium). High intracellular calcium levels lead to higher blood pressure and more cellular fat.
This metabolic fact— that low dietary calcium raises intracellular calcium—has been called the ‘calcium paradox’, and there is now plenty of medical evidence linking this to the development of arterial disease and diabetes. With a large vegetarian population that avoids sunlight, India is now seeing an increase in heart disease and arterial disease, even in people who seem to eat otherwise healthy diets. It therefore seems logical that the first thing we should do is screen anyone from the Indian subcontinent for vitamin D deficiency, yet this is still not done in primary care as part of routine general practice. Current medical practice is seriously lacking in this regard, and being penny-wise and pound-foolish in my opinion.In New Zealand, where I have a home, vitamin D tests aren’t even fully funded by the national health system!
And while we are educating doctors, perhaps we should also be teaching the origins of skin colour differences to children at school. The world would be a much better place without racism. After all, it isn’t a coincidence that “varna” in Sanskrit translates as both “caste” and “colour.” Biology has no bias; alas, bigotry does.
Sharad P. Paul is a doctor, writer, evolutionary biologist and professor at the Auckland University of Technology. He was the speaker at the ZEE Jaipur Literary Festival and at The British Library, in London in celebration of 70 years of UK-India relations.