For sake of discussion it's worth making a clear distinction between marriage in the legal and cultural sense, and pair-bonding in the biological sense. In the legal sense, it hasn't served evolution because it hasn't been around long enough. In the biological sense, I suspect (but I don't know) that a percentage (no idea what the number is) of Homo sapiens individuals are strong pair-bonders and some not; maybe a spectrum? Would be interesting to know, if anybody has any info on this.

In any case, I don't think it is just a matter of social consensus. I think biology plays a large role.

I don't participate in traditional marriage but it still has a purpose in society. As we further divorce from each other as technology advances, the nuclear family ideally recreates the supportive village of nurturers.

Marriage is fun, it gives a sense of responsibility, it comes with a network of new people who might be able to do stuff for you, it tends to ensure that there will generally be clean clothes, hot meals, and a roof. But is it necessary anymore? Probably not.

Monogamy has never been neccessary for propagation of the species. In fact, we'd probably still be swinging from the trees if we had developed as monogomous beings.

If you think about it, in the early days of human development there were likely very few bipeds who demonatrated those characteristics which would eventually grow in to higher thinking skills. If they had not frequently shared genetic material, the odds of their survival would have basically been non-existent.

I got my BA in Sociology. For the mos part humans are NOT monogamous by nature.

The rich and upper classes marry for business purposes and gaining alliances, and usually the man, if not both, in the marriage will have lovers outside the marriage.

Marriage was originally a business deal to tie tribes together and to make alliances. Love marriage are a relatively new idea in human history. Teh ideal of a love marriage has existed a lot longer than it has been practiced.

There is a reason why the tupical marriage vows say "for better or for worse". Infidelity is a part of the reason.

The best marriages I have seen or witnessed, have nto been wholly monogamous, but have been wholly honest. If your partner or spouse is honest about having had a fling, chances are you probably have nothing to really worry about, as if they tell you, then they are nto about to leave you. If they keep it secret or lie about it, then yo have to worry. Secrets in marriages are like wedges driven between you emotionally. You cant' remain that close to someone if there are secrets between you.

I'm against marriage, at least for myself, and I think it does more harm than good. That's not to say I'm opposed to good, loving, devoted relationships, but that I don't think formal, legal documentation fosters that connection and can indeed undermine it.