There's also enormous pressure to make your marriage conform to the standards of your culture too (or ideals cause they aren't really the standards). Which is a huge contributer to divorce.
I read a fantastic book called Sex At Dawn a while back which is about the evolutionary history of sexual relationships and how generally through most of our evolutionary history the model we have now has not existed and even when we did start to form possessive pair bonds, monogamy while it was the message was not at all the norm. It also goes into a lot of really interesting stuff about group dynamics, genetic inheritence and a wack load of other topics all from a scientific/academic perspective.
Again not that I think everyone should be fucking around with everyone and their brother but until people break the association in their head that desire = love they'll always get in trouble cause you have to have enough emotional insight to separate the two or you make the mistake of thinking you're in love when really you just wanna tap some hot 20 year old (and do it cause you think it's love).
Here's Dan's monogomy is like sobriety talk:
http://bcove.me/uitg5o2p