[paxys]

To put it more simply - marriage was created for a man and a woman who were both fulfilling strict social expectation of their gender. Man would hunt for food & protect the tribe, which eventually turned into work a 9-5 job and earn money. Woman would manage the house, cook food, raise kids.

It has increasingly less place in the world as lines between gender roles continue to blur.

[jhanschoo]

I disagree. Throughout most of history, people lived in extended families, and only recently (starting from 1900s) has it become nuclearized for most of the people.