Also, a protein called attractin is known to regulate both melanisation and immunity in humans, suggesting a link between the two. He also points out that darker-skinned people are less likely than people with fair skin to develop serious skin diseases. During the Vietnam war, for example, American soldiers from a variety of racial backgrounds were sent into the Mekong Delta. It solves a lot of problems with these other theories. It also explains why we don't all have black skin.
Melanin is made from the amino acid tyrosine, which is also needed to build proteins.
In prehistoric days when food was scarce in cold, dry areas, tyrosine was probably conserved to make essential proteins, Mackintosh says. It was only worthwhile converting it into extra melanin in the warm, damp tropics where food was abundant and pathogens were rampant. Recent Science News .