With god and religion out the window, something about this subject confuses me, and this is mainly due to many of the dynamics involved in relationships between two romantic partners. Sexual jealousy is something that can be explained well under Darwinian terms, but also Darwinian explanations can also be used effectively to explain "cheating", or at least when a partner has a fantasy about sex with another person outside the relationship. To me this seems like a type of Darwinian double standard that is engrained in our nature. Cultural norms have emphasized monogamy in relationships, and these norms can be seen as obsolete, especially with the invention of effective birth control. But yet, there are many shades of gray involved in the morals about sexual infidelity and jealousy. It can be argued that the consequences of sexual behavior, if performed without precaution, can lead to the birth of a child. It is far easier for two parents who are living together in today's society to raise a child than it is for a single parent, and this is mainly due to economic reasons. Could sexual jealousy have something to do with that? I am not satisfied with the idea of a Darwinian double standard, and perhaps I am overlooking something important. And so it appears to me that if I put the question of sexual jealousy into the terms of nature verses nurture, could this simply be a nurture question?