Technically speaking, one can form multiple "pair bonds". I'm differentiating between actual polygamy and casual sex.
I should have been more specific and said "exclusive pair bonds." I was also differentiating between polygamy and monogamy.
The best statistics we can gather show that infidelity is nearly equal between the sexes. I think those cultural influences you are about to list below are skewing your perspective of female desires. Women may want only one man during reproductive seasons, but that's not a constant state, and even as it is, while it might be one man it doesn't have to be the same man.
I was talking about how desires such as this can be due to the person being subjected to outside influences. For most of our evolution, we were not surrounded by nearly as many sexual stimuli for the purpose of pleasure, and attachment to mates and children was vital for survival. That's why the chemicals involved in love and attachment are produced during sex.
Because people think sex = srs reltionship. Sex is not homogeneous. There's quite a different dynamic in specifically trying to reproduce with someone vs a blowjob in the alley.
Part of what makes sex pleasurable in the first place are chemicals that create nurturing and attachment. While people do not always use sex to bond with others, that doesn't change the fact that we evolved a mechanism in our brains to induce/strengthen bonds and attachment as a result of sex.
Essentially, my point is that sex creates/enforces bonds in humans, and the cultural attitude of sex as meaningless, casual pleasure makes bonds meaningless and casual, and thus harder to maintain, which I think is the cause of the rates of infidelity.
In other words, sex has an initial role/relation to bonding and attachment which the surrounding culture (particularly mass media) detaches from its original role, causing higher rates of infidelity.
Of course, I think this could only really be measured if one were to check oxytocin levels of promiscuous people against the levels of those who are monogamous. My hypothesis is that sexually promiscuous people produce it for strangers faster, but also lose it more quickly than monogamous people. Also, the levels that sexually promiscuous people develop are lower than those in monogamous people, high enough only to gain pleasure in sexual intercourse. In other words, monogamous people have higher, more constant levels of oxytocin than promiscuous people, and thus are more capable of sustaining faithful, stable relationships.
I guess what I'm arguing is that sexual promiscuity is a capability of our sexuality, but not the root of it. The root of it is in mating with a partner that one protects/receives protection from so that the offspring can safely be born and raised.