This question was closed as opinion based: Is monogamy a human innate behaviour?
I'll bring up the two reasons I've encountered so far. If the authors want to elaborate or explain why my objection is wrong (or better yet vote to re-open the question), that would be appreciated.
I voted to close this because of these two words: "by nature". Neither the question nor the answers define what on earth is "by nature". While OP or someone else don't do it, this question must remain closed.
To which I replied (with grammar fixed):
I don't think questions should be closed because we don't understand the meaning of two words that are well defined in the dictionary, especially when every word thereafter makes the distinction being made abundantly obvious. Furthermore, the classification of primates based on mating behaviour is a scientific endeavour, not something mired in opinion.
...I don't think this question is really answerable, at least in its current form, except for some non-answer where you state that monogamous and non-monogamous relationships exist therefore yes, humans are by nature monogamous and non-monogamous because there they are, in the nature of human society, forming both types.
You first have to litigate "what is nature?"/"what is natural?" and that is wholly off-topic.
The OP has since edited the question to remove the word "natural". In case I was wrong (hard to imagine such a world) and the question is not "abundantly obvious", it is asking whether monogamy is the result of our complex and relatively modern society or if it evolved pre-civilization. The evolution of monogamy in humans has been the subject of many peer-reviewed articles (examples: one, two, three) and thus I don't understand why this question was closed as opinion based.