One other consideration: I recall a 20/20 special years ago that showed how superficial society can be. They did a test where they had one 'unattractive' person on the side of the road who had no gas and needed help. Needless to say, they never received any help in comparison to the 'attractive' person who was put in the same situation.

The point that I'm making is that, maybe the reason why 'attractive' people may have a higher IQ, is that they are more likely to receive help from others based solely on their appearance.

Another point I would like to add: Maybe 'attractive' people feel the need to increase their intelligence, due to the stereotype that 'attractive' people don't need to have intelligence and can just rely upon their looks to get them through life.