a) Genes are not expressed the same way in men and women. To oversimplify a little, if a gene is only activated in the presence of male levels of testosterone,

a) Genes are not expressed the same way in men and women. To oversimplify a little, if a gene is only activated in the presence of male levels of testosterone, it will not be expressed in women. In the long run, natural selection hooks up genes that are beneficial in men and harmful in women to testosterone-sensitive gene promoters, though this may take a long time, and in the meantime you may end up with women with deleterious traits that were beneficial for their fathers. While we're at it, similar mechanisms account for the difference between a neuron and a muscle fiber, which share identical genomes. b) A very successful man can end up with hundreds of concubines and children. A significant percentage of Asians are direct descendents of Genghis Khan, and there was a King Niall in Ulster who is said to be an ancestor of 25% of the men in Northwest Ireland. Monogamy somewhat limits this in our culture, but most people for most of the time humans have existed have been polygynous. For a woman, this is impossible - she can have a dozen or so babies at best.