Reddit reviews Sex with Kings: 500 Years of Adultery, Power, Rivalry, and Revenge

That's a really long time span, across a pretty wide geographical area, so the answer will vary as to how common it was. I'm most familiar with England and France, between the 11th and your cutoff of the 15th centuries, so I'll limit the answer to that.

First of all, the Catholic Church changed its opinion on the issue of prostitution in this time period, moving from condemnation to a tolerant-but-not-approving view of the subject, based on the view that lust is a capital sin, i.e., it causes people to commit secondary sins in the pursuit of it. A man overcome with lust for a married woman, for example, might break into her house and rape her, or murder her husband. So in the view of the church, as seen in the writings of Thomas Aquinas on the subject, allowing prostitution to be legal was like putting a sewer in a city. While unpleasant, it prevented the filth from overflowing into the streets. (Note this is contrary to what /u/shevagleb was speculating below, who presumed that the increase in church power would mean greater restrictions on this sort of stuff.)

The Sexual History of London is an easy to read book on the subject, and goes into how the Church was actually responsible for running the brothels outside of London. Being "Bitten by a Winchester Goose" (which meant getting an STD) was a reference to the fact the girls were employed by the Bishop of Winchester.

For extramarital affairs in the rich, Sex with Kings goes into all sorts of fun detail on the nobility and the affairs they had with each others wives. (It was considered less scandalous to sleep with another person's wife than a single woman, since a single noblewoman getting pregnant would create a scandal, while a married woman would have a somewhat plausible smokescreen.)

Extramarital affairs with French kings were so standard, that they developed an official position at court for them, the mistress en titre. They were presented in court when promoted into the position, and had to go before the Queen, who would receive them along a spectrum varying from outright insult to complete acceptance.

One of my favourite books is Sex with Kings. I wouldn't recommend it as a reference for any academic papers but it's an interesting read about, well, the sex lives of past kings. Can't really use it as a gauge for societal norms but in some ways, their lives were much more well documented.

Henry VIII had a string of nubile young mistresses. By the time of his marriage to 17/18 year old Catherine Howard, he was a middle aged, morbidly obese man with a festering ulcer in his leg. It probably wasn't pleasant.

Peter the Great was apparently famous for his drunken orgies. Many of which were with cheap prostitutes (he was also very thrifty).

Ludwig I (King of Bavaria) wrote some intensely descriptive letters to his exiled mistress, suggesting that they regularly performed oral sex on one another. Or that he masturbated as he sucked on her feet (she was a dancer, maybe he had a thing for feet).

So, I would say, even back then there were plenty of kinks abound. :)

If this were true, you wouldn't see any macho behavior among Islamic men. But in reality their culture upholds the "macho" thing.

>Feminism implies female choice.....all of them, at the core of their beliefs, want women to have 100% choice over who their partners should be.

Yes, given that this is a basic human right.

>In a patriarchy, where we have arranged marriage and men don't have to compete in mating rituals like some sort of uncivilized monkey, men don't have to worry about being a machismo alpha male and instead can just be themselves.

Except in patriarchal cultures, men still compete for women. Typically the more powerful and alpha men in arranged marriages didn't stay faithful to their one wife. They married a woman for political reasons, but still chased after other women they wanted as mistresses (sometimes even after those women were married off to other men).

So no, men would still compete for women even with no-choice forced arranged marriages. And actually, even taking women out of the equation, men will always vie for each other for other reasons too: wealth, power, position, status.

Really, I'd suggest getting a bit more well-versed in European history. Especially given how pro-European you are, you ought to know your own people's history. I think you might benefit greatly from taking a history course if you're still in college. Or just read some books about prior European eras where romantic customs and marriage patterns were different. This one is particularly enlightening.