Hi, I've always noticed that my penis is always tanner then the rest of my body(when i don't have a tan). I was talking about it once to a friend and he said his wasn't. Then a few days ago, a friend of mine saw some 'photoshopped' gay porn pic and said it was obviously fake because the tan was different(i'm not sure why thats the first thing he noticed but w/e). That obviously shows his is the same color as the rest of his skin like the previous friend. Now this was on AIM so I copy and pasted that to a third friend, who then informed me that his is darker then the rest of his body like mine is.
My question is, why does it seem that some people have darker pigmented skin only there, and others don't? why does that happen? and which is more common?