Yes, it’s not unusual in nature - though we’re supposed to aspire to superiority over them, not lower ourselves to their behavior.
There are conditions where total monogamy would be detrimental to a society, such as a small (tribal) population needs to stir the genetic pot, or a gender-lopsided one (war having killed off significant fraction of males) needing mates in lieu of population collapse. So there has been a species-survival benefit to keeping monogamy predominant but not exclusive.
Why the Left is so he11-bent on outright destroying monogamy in a large & stable culture, however, I don’t yet understand. Maybe it’s that enough of them _haven’t_ been that they would feel overwhelmingly guilty if non-monogamy remains frowned on (if not prohibited outright) - kinda like abortion, tattoos, and other major irreversible mistakes.
The Left just seems oblivious to the objective reality that the activity is about _procreation_ - fun as it is, and preventable as consequences are, all too often “life finds a way”.
It has always been a major goal for the left to destroy monogamy. When you understand why then you will understand the left.