Here’s what I read in one of cecil’s columns http://www.straightdope.com/classics/a2_317b.html:
it seems to me, we might just as plausibly conclude that the reason our hair is brown (most people, anyway) is that it enabled our monkey ancestors to hide amongst the coconuts
Apparently the straight doper believes that most people have brown hair. The teeming billions in China, India, Africa etc. may beg to differ.