Monogamous animals don't adhere to belief systems...and they do exist therefore monogamy is natural and clearly predates religion and conditioning in my opinion. That being said, Monogamy is definitely a relationship ideal as well though, just like polyamory is both a nature and a belief system I feel.
Which one do I think is the most productive belief system to base a social structure on in a modern capitalist world? Monogamy…specifically serial monogamy because I don't think monogamy is defined by only bonding with one person over an entire unnaturally long lifespan. Polyamourous people spend more time making connections and managing relationship dynamics than mono ones from my point of view and experience. For the most part the major difference I have observed between my old mono community and my newer poly one is the level of success in a capitalistic world. More possessions, more money, more financial and career stability. Why is that? Stability in the relationship allowing for more focus in other areas. Does this make it better as a relationship structure? Absolutely not. It does however give the impression that society has a way of migrating to the most efficient way of doing things to achieve certain forms of social structures. Big capitalistic modern societies generally migrate to monogamy regardless of whether the people involved are all mono or not. Low tech, more nature orientated societies or communal living populations seem to share more, love more and have a greater appreciation for all life and co-existing with the world around them.
Which structure dominates the world and likely will continue to do so? The one with global power and influence - the one we're currently in.
In order for things to change more than just beliefs have to evolve, humans do. What our desires are and what we value as a global community needs to change or whatever structure that supports them will remain dominant. If that structure continues to dominate than that is either what the bulk of society wants or we are being controlled by some very clever and well positioned people who are imposing their beliefs on every one else.
Playing the Game of Life with Monopoly rules.
Monogamy might just be in my genes
Poly Events All Over