What is up with marriage? How did it start and why do people do? Is it an institution?

Then don't get married - there are plenty of people these days who do not get married and it's not a problem. If you feel that marrying one person will lock you into something then don't bother. I think there are too many people who marry for the wrong reasons - that's why 50% of marriages end in divorce. But sometimes people do get lucky and find that one person they can't imagine life without. My parents celebrated their 45th wedding anniversary last year and they are still in love - they go away on romantic weekends together, my dad still buys my mom flowers for no reason, they walk down the street holding hands, etc. They are getting older and I honestly believe that when one of them passes, the other is not going to hang on for much longer because they are really halves of one entity