I suspect that people who want to call it biology are loathe to examine the complexities of choices and free will, etc.
bestofus, I would argue that many people do not use self-examination and make a conscious choice for monogamy. Just like people don't make a conscious choice (often) to be straight. It's the default, it's the majority. Most people don't even know there's any other option. In order to do something different than the majority, one has to feel, and believe, and examine, and question, and CHOOSE.
Sorry, Derby, doesn't seem like we're helping much with your premise.