What is 'sexy son hypothesis' in Biology?

This is a theory of mating preference which states that women tend to pick males with the genes to create attractive sons as their sexual partners. The rationale behind the hypothesis is that attractive male offspring possess the best chances of procreating and passing on the mother’s genes to the next generation. It also implies that a man’s ability to successfully provide for the mother and the offspring exerts only a secondary influence on mating outcomes. The hypothesis was proposed by British biologist Ronald Fisher in his 1930 book The Genetical Theory of Natural Selection .