The day we’re born, each of us opens our eyes and begins to build a world that seems “normal” to us. It is built from scratch, experience by experience, and what we build depends on the die roll of where we’re born and when. So what we come to regard as “the way things are” may only be the way things have been for a few centuries, or even a few decades, and only in our own locale.
We have a tendency to project our own “normal” backwards and forwards across time and across millions of other people’s lives, making a lot of people wrong in the process. The irony is that we refer to these relatively new practices and social rules — of which monogamy is only one — as “traditions,” and that any deviation from them is a betrayal of what’s natural. Ninety-nine percent of human existence occurred before the “traditional” ways even began.