"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea." I was thinking about this yesterday looking at someone's eyes and was wondering if it was as simple as blue eyes being pretty. I know we usually find as 'pretty' the things that have an evolutionary advantage (hips, muscles, etc). But what about the other way around operating also? If someone had very rare, lovely blue sapphire-like eyes (instead of brown, which is a much more common color in nature), wouldn't that person have appeared more special in the past? i've heard boys like blue because it's part of our training, to find water (and girls like pink to help find ripening fruits). we're predisposed to like the color, and it happened rarely, we mated more with those people, and hence the number of blue eyes increased dramatically?
You describe Darwin’s hypothesis, that blue eyes were sexually selected. It’s a fair possibility. A problem with the hypothesis is that blue eyes are mostly recessive, meaning that most people who have blue eyes have two copies of the allele. That wouldn’t happen after the allele first originated because there would have been too few people carrying the gene.
Possibly the mutation’s initial success was due to chance, and when it go common enough sexual selection took hold. Or maybe there was selection on some other phenotype correlated with the allele – in which case we have yet to identify the actual target of selection.