Still, the incentive structure of marriage until basically yesterday was "hey, I am publicly announcing this woman is mine and I will brutally kill anybody who tries to seduce or rape her, because that would put me at risk of spending lot of resources on an offspring that's not mine. You can't say you have not been warned. Also, my family of origin and her family of origin now have a shared interest (namely, making this family prosper so that their grankids can flourish) and it's better for everyone if they go along, so let's throw a huge party and keep good vibes" Like, we know that. We don't need wild conjectures about what is the incentive structure of marriage, people have been pretty upfront about it for centuries. And if you really have to chase wild conjectures rather than empirical evidence, the least you can do is not to start from laughably culturally specific assumptions: the idea that a social institution serves to maximize individual happiness, when for most of history (and in most of the world still today) that notion would have been bizarre if not frowned upon, can only lead to wrong conclusions. Again, people across cultures and centuries have been pretty upfront about the fact that the point of marriage was not to help any of the spouses be happy but just to keep society working in an orderly manner, or to help spouses adhere to some transcendent morality. The only thing you can get out of this story is a huge warning about the implicit modus operandi of rationalism: the dangerous idea that you can deduct reality, from first principles summarily chosen from what seems common sense in XXI century America, and that the result of building a huge tower of these frail bases can somehow be substantial.