A lot of the practical history of the family and its structures is down to economic/resource pressures that we - as an increasingly wealthy & complex society - are slowly finding ways of working around (note the vast expansions of healthcare, social care, welfare safety nets, transportation networks, employment options, luxury consumption, etc, etc, etc). I think that's a fairly irreversible process. What remains to bind couples together on a vaguely permanent basis is increasingly only the residual ideal of love. It will be interesting to see whether that remains enough as the generations continue to pass. It will for a long time I think, at least in theory (in practice, people will marry increasingly late, and even so, divorce rates will remain high), but at some point, a new concept that fills the same human need to have a manifest destiny, will probably overtake it in the popular imagination.
Interesting question, for sure.
This ties into my view on relationships, marriage and love.
It is a view that most people probably critic as un-romantic.
I have long since accepted that relationships have an expiration date. Life long love and romantic commitment is possible but in the minority.
Taking into account that most people have multiple relationships in their life, and no one plans to only stay together for x number of years (if it even gets to years).
The notion that you are supposed to meet your partner for life, 60-80 years, during or shortly after school is ridiculous.
That doesn't mean that any relationship that doesn't last until we die was a waste of time.
The opposite in fact.
having multiple relationships and loving different people during different stages of our life is an integral part of making us happy.
The art of recognizing the natural end of a relationship and discontinuing it without ill feelings toward the other is what makes a relationship ultimately successful in my opinion.
of course, it doesn't mean, that one of the partners won't get hurt in the process, but everyone should realize that ending a relationship is just as much a part of love as beginning one and it's not a terrible tragedy.