we've got a 50% divorce rate in marriages, with the other 50% involving cheating, murder, boredom, and dissatisfaction.
But it's probably less than 15% of the 50% that those things apply to, people can be happily married but the rest of them should never marry in the first place.
If Christainty hadn't spread across the west and Roman ideals of sex were still floating around, we'd be living in a world where it's acceptable to have multiple partners AND partners of the same sex.
We'd also be living in a world where STDs would be a bit more of a problem although they might have helped with population control, actually we really don't know how the world have become over the 1700+ years that Christianity wouldn't be working...