Increasing urbanisation is cutting off people from adequate sunlight, which helps the skin produce vitamin D, facilitating the absorption of calcium, says a study.
About two million years ago, permanent dark skin colour imparted by the pigment -- melanin -- began to evolve in humans to
regulate the body’s reaction to ultraviolet rays from the sun, said Nina Jablonski, professor of anthropology at Penn State
University.
Melanin helped humans maintain the delicate balance between too much sunlight and not enough sunlight.
The pigment allowed enough ultraviolet radiation to produce vitamin D, while protecting the skin from the intense ultraviolet radiation in the equator. Too much sunlight can cause the destruction of folate, which is also critical to cell division.
Unlike their ancestors, modern humans are more mobile. “We move around a lot now,” said Jablonski.