Having failed to understand Holk's post, I'm going to clear something up with this Laguna fellow.
Here's something for you: humans have one of the largest times spent in childhood in the entire animal kingdom. That's because we have to be brought up gradually to be able to use our dang fantastic comparatively massive brains. We are born weak and fragile and fucking stupid, and we are raised over
years to become barely independent beings that thrive because of our interaction and close ties with others.
Why does this relate to what we're talking about? Well, who's going to raise this idiot for the 20 or so years they need to be raised for? The mother's not going to be able to handle such a ridiculous task coupled with her life and other children. Who else does this baby belong to? It's fucking dad. Yeah.
So humans stayed in couples for the children, and learned that it made a social connection that evolved into the emotion we know as love, and groups that we now call families. A perfectly logical evolutionary reason for why people should stay together.
Now, the polygamy thing is a little different. Think about this; back in days when there were NO contraceptives, polygamy (or, fucking anything that gives you a look as animals know it as, and our ancestors knew it as) meant lots of babies. Mothers had to raise these things as their brains got bigger and because of this brain thing it took a lot of time and effort. So the child's father was inevitable brought into the mix. If the father kept making babies and then have to help raise them, he realized that maybe he'd be better off being with one female.
Another evolutionary reason for monogamy, right there.
So, if the father make lots of babies and the mothers couldn't handle raising them to their full capacity, we wouldn't have been nurtured to the point where we needed to be, and in turn we wouldn't have our super-brains and consequently would not have conquered the planet. The fucking duck or something would've taken over.
Where are his computers?
Monogamy's got the entire history of civilization as its score; what's yours?