(A response to a friend's discussion of the biological basis of one-night stands)
There is a scene in "The King and I" where the King of Siam declares that men are to be like honeybees, travelling from flower [woman] to flower. The converse, of course, is not true, and he holds that female polyamory is analogously unnatural. On one level, on a level of evolutionary biology, he is quite correct. Men indeed appear to be programmed to spread our seed far and wide, in a way that women (obviously) are not. For whatever reason, this holds true even for those of us whose sexual orientation is inverted.
The naturalistic fallacy and the "is-ought" problem definitely come into play here. Because many of us, if left to our own devices, would conduct our sexual lives in such a way as to have a clear disregard for our partners. It is often stated that men will "say anything" to "get some." And I think, on a purely natural level, there is a certain truth in this. I recently escorted someone to an Alcoholics Anonymous meeting at which the speaker defined alcoholism as the condition wherein the obtaining of alcohol becomes a priority - even over the feelings of others. Men certainly have a tendency to behave this way in regard to sex.
Locating myself as I do within a particular theological tradition, but like any ethically-minded person, I am obligated to avoid making decisions based purely on what is "natural." Virtue is unnatural. Altruism and selflessness are unnatural. But all of us, not only those of us who "believe in a power greater than ourselves" can ever seek to behave in a manner that is loving and ethical, with a healthy disregard, when needed, for that which is purely, amorally "natural."