In early October I was on a holiday near the equator and got tanned. Now, roughly 3 months later, the tan on my face and arms has gone almost entirely where my belly, chest and legs are still moderately tanned. It seems that body parts that are exposed (to light) more than others seem to loose the tanning effect more quickly. Why is this? Or is there another reason?
I am not a biologist so I would appreciate an answer that is articulated in a way non-biologists can understand it.