Male Baldness Info

Going along the lines that people who live closer to the equator are darker skinned, I have often wondered about the evolution of human hair. I don’t know much about evolution, perhaps some of your expertise in the matter may enlighten me. I assume our evolutionary ancestors were covered with hair. I can understand why the last hair to go is that found in the pubic area, because of sexual/reproductive reasons. Underarm hair isn’t so clear to me. But what I’m most inquisitive about is hair on the head. I assume it has remained there for protection. What, then, explains male-pattern baldness, and where does it fit in the evolutionary equation?

You know the round spot in the back. Or the high front hair lines in the front..