There is no question that at least in the modern western world, marriage is not just deteriorating, but also diminishing. One argument for same-sex marriage is the breakdown of hetero-sexual marriage. I am not sure how that legitimizes a redefinition of marriage, but it is still made.
It is also debated whether through God or evolution, marriage came to be a relationship for family to exist in a healthy way.
There is no honest question but that major religions agree that marriage is a divine creation between a male and a female. Government involvement has been simply a consequential confirmation to facilitate certain elements (Mainly the safe raising of children.) of a sacred union.
Evolution presents a whole different scenario. If gender and marriage evolved to facilitate child rearing, it can also evolve to something else when marriage becomes unnecessary. A relevant example would be the bee colony. A queen bee reproduces, female worker bees facilitate the hive, and male drone bees simply fertilize the eggs and then die. I assert that this could be a very real possibility for human evolution.
Until recently in the western world, and still in most of the rest of the world, the roles of husband and wife were/are very clear. The male is the head of the home (Doesn't that push buttons now...), who provides for and protects his wife and children. The wife manages the home and children.
Now, the glass ceiling has been shattered (Or maybe broken...). Simply put, anything a man can do, a woman does. As Jennifer Aniston recently put it, that includes birthing and raising children without a male. In addition, the father of that child has absolutely no say in whether his child is even birthed or aborted. He is at a disadvantage in the case of a divorce, especially regarding custody of the children. In job settings, any minority participants are many times given an advantage.
The question can reasonably be asked now,“What are men good for?”“What needful purpose do they offer?” We have gone from John Wayne to Charlie Sheen. Self care for many males is the only responsibility they have. Could that be a part of why men are most often portrayed in the media as 'jerks'? Or even the breakdown of gender distinction?
This change is even more profound for women. While men have had purpose removed (Think about that...), women have had full responsibility loaded on their shoulders. Makes me wonder if evolution has had time to keep up!
Marriage is caught in this change. What was once a crystal clear identity and purpose is now weak and fuzzy. Is it any wonder a change of definition is pursued?
I have not made any judgments about this change so far. But that question begs to be asked. Think of the social experiment we have engaged in! Have we really thought out the implications (For men, women, children, social structure, etc.)? Has this 'progress' been beneficial so far? Does history give us a example (Amazon women?)? Have we considered where it will end?