Darwinian evolution has been used to explain variations in species, but when it is applied to social interactions it is mostly conjecture and not a lot of empirical evidence. Sex works for procreation, but that it not the only reason. Frankly I just enjoy it, the pleasure of being united with my husband, the pleasure, closeness and security are all part of it. I have been told by 3 different physicians that I cannot get pregnant again, but that in no way has changed my sexual desire. In fact it may be stronger than ever. I would love to still be having sex at 90