What is marriage?

Is is apparent that marriage is very much up for grabs at the moment. Or at least how we want it to be enshrined in law at any rate.

Part of me wants to go with the flow on this one … this affects people close to me … but another part of me is saying “Whoa! Think carefully and critically about this … this is no small thing that we do.”

Someone much more thoughtful than me has framed this question. I think it will (with intended bias) help answer the question.

I can think of no culture throughout history that has not had some sort of form of marriage. If humans were asexual (meaning that an individual can reproduce) do you think that any of these cultures would have developed this thing we call marriage?

What do you think? What is marriage?