Monogamy is more than just a relationship structure, and this is what kills me when I see the argument that "monogamy is <x>". From my POV, there are two aspects of monogamy:
1. I only desire one person romantically at a time
2. I want my partner to love only me
I was in a rush. Sorry about that -- we use words differently. To clarify... to me?
"Monogamy, polygamy, polyfidelity, open, closed, triad, V, quad" -- those kinds of words are describing the relationship structures people could be in.
The desire for only one person to love romantically at a time to me is "monoamory." The desire to love many to me is "polyamory." I think there are some people internally wired for mono- and some wired for poly-. Just like some people are wired for fast or slow metabolism or whatever trait. They just come wired how they come.
"Monogamy" and words like that about relationship structures are more "society/culture" things than "biology" things to me though. A polyamorous wired person could choose to be in a monogamous relationship structure. A monoamorous person could choose to be in a "V" structure.