19ish% of CIVILIZATIONS or cultires across time have been monogamous.

But that doesn't equate to couples or mating pairs.

That worked out to be an estimated 58% of couples are monogamous suggesting two things.

Not proving. Suggesting.

1. It's possible that monogamy is a significant part of many civilization's long term success. If more couples pass through monogamous civilizations than non-monagamous ones the it stands to reason it's because those civilizations last longer and/or grow larger than non-monagamous ones on average.

2. For some reason, humans tend to drift toward monogamy. There's some mechanism in our social bonds or something that drives or keeps more of us in monogamy.