1) whilst I get your over all point and where you are coming from (people can do what they choose etc), I am not sure why you assume non promiscious people are "prudish". I love sex and have a lot of it but with someone I am emotionally and sexually attracted to.
2) I am willing to cover these topics from both a male and female perspective. Men and women have bonding hormones called vasopressin and oxytocin which surge apon orgasm. This is believed to help promote infatuation (the initial bonding stage before love) so they will have soo much sex together that their dopamine hormone will kick in and over time that makes them addicted to each other. Not just sexually but emotionally as well. It is believed that some males and females have a hormone imbalance which can prevent this bonding from occurring. Some males, for example have too much testosterone making them more sexually driven, less emotional and more selfish. Some males are lacking in vasopressin making them less protective, less possessive etc of their partner and more likely to cheat. Some women are lacking in oxytocin making them less nurturing, less emotionally driven and more likely to have superficial relationships (such as marrying a sugar daddy for example).. of course all of this affects parenting as well-hence why some people make terrible parents..
These same hormones (oxytocin and vasopressin) surge when a woman gives birth or when a male holds his offspring for the first time which explains why some women orgasm whilst giving birth or breast feeding (because it is the hormone they usually associate with sex). Some men have even been known to become semi arroused during the initial bonding stages with their newborn which obviously deeply disturbs and confuses them but its because the bonding hormones are the same ones that made him fall in love with the childs mother.
3) Certain animals (such as wolves) are very similar to humans in this way-having very similar pair bonding hormones. Apparantly dinasours did too.
Anyway according to dr phil and Gary Chapman and Robert weiss (all male relationship counsellors and robert weiss is also a sex addiction expert) one of the ways to spot a man with high vasopressin levels (husband material) is that he doesnt sleep around or show a desire to.
4) There are so many articals promoting non monogamy and sexual freedom. So many of these have zero scientific or biological evidence to back that up. The reality is that monogamy hasn't been studied in great detail until recent years and it is only now that the scientific/biological evidence is there to give a truly thought worthy argument.