Question

What is one indispensable function of UVB rays in the human body? How does this exert evolutionary pressure on human skin color?

Answer 1

UVB rays cause sunburn and are responsible for skin cancer and pre-mature ageing. These rays have medium wavelength and affects the top layer of the skin. The main function is melanin production or photoproduction of Vitamin D3. Since UVB directly impairs DNA, there are many evolutionary changes like loss of scalp hair as seen in African population. variation in skin color is also an evolutionary change because people staying close to equator shall have brown pigmentation or black color.