Caucasian blondes are usually slightly higher in oestrogen than brunettes and are likely to exhibit other infantile sexually selected traits (indicating low levels of testosterone) that are considered desirable by males, for example finer facial features, smaller nose, smaller jaw, pointed chin, narrow shoulders, smooth skin and less body hair, and infantile behaviour such as higher energy levels and playfulness

via www.guardian.co.uk

Science doesn't do political correctness very well. ;-)

That said, I married a redhead...