What exactly is the reason behind it? As a hetero-blam!- man, the main reasons I would get married to my future wife is to get emotional and spiritual consent for myself to have kids ( I'm Christian), be able to as the Flood says "stick it in her poophole", and feel bonded to my wife... Now 2/3 of those things will serve good for humanity because I'm evolving it as a population.... As a homo-blam!-, from what I have heard, I would pretty much get married for only 1 of those 3 things I listed before (feel bonded to my partner), and it is the one that doesn't benefit evolution at all!