We often talk about testosterone in males, and perhaps not quite as often, estrogen in females. This is a great episode of Quirks and Quarks in which Bob MacDonald interviews a researcher who has looked at the effects upon the brain, (and resulting sexual behaviours,) of both women and men with low vs. high testosterone levels, and the difference in the perceived attractiveness of females who have high vs. low estrogen levels.
Relating to the previous post, he discusses how we have evolved out of high-dependence upon our olfactory lobe, but that female brains "light up" the more the odour of their partner is a contrast to their natural order, and this is an attraction that promotes genetic diversity.
Near the end (15:00), there is discussion of how our brain is able to become chemically dependant upon sex based on the the chemicals it releases, and the importance of oxytocin and vasopressin in relationships. Could we have genetic variance that results in some people being more genetically suited for monogamy?
Enough said--take a listen and post any thoughts on the interviews on this episode (from 1:40 - 22:40):