On the poly thread, Dan, I think a key component of understanding this question is the context in which died-in-the-wool (if you will) polyamorists live out their poly lives while to at least some degree swimming against the larger mainstream cultural tide. You know, of course, what that's like. Trusting in ourselves and our own sense of who we are and what is right for us, without shame or apology, becomes an essential component in withstanding the blow-back we get from people whose esteem we care about and whose tolerance, if not acceptance, we value. That sense of identity becomes the bedrock upon which we can build a life that will withstand the external cultural challenges we sometimes encounter. As I am fond of saying, polyamory ain't for sissies. These challenges take the form of drama and rejection by one's family of origin, the loss of friends who don't approve, loss of a job because the boss starts to question our judgment, or loss of child custody due to false assumptions by family court judges.
As you point out and as Chris Ryan and Cacilda Jetha well demonstrate in Sex at Dawn, humans are naturally non-monogamous - of course! But over the centuries religious authorities' literal crusade to force people to conform to monogamy became a very effective barrier to patterns of relationship openness and non-monogamies of all kinds. Still today, living a life of integrity as a polyamorist requires a significant amount of swimming against the tide, and that's putting it mildly.
So with that perspective in mind, you asked:
"...is poly something anyone can do ...?"
Yes. Or at least, the majority can if they want it, but not quite everyone. In my experience, those who want it enough and who are committed to doing the work necessary to live comfortably outside the societal relationship box and make the transition from monogamy to polyamory absolutely can do it. The exceptions are those who have significant self-esteem and/or abandonment issues. Likewise as to those who lack self-awareness, live in denial, and don't own their own feelings. It's also essential that we learn good communication skills. Mental illnesses, anxiety disorders, depression, malignant narcissism, and oppositional personality disorders are generally prohibitive. Otherwise, anyone who is reasonably well adjusted, open to new experiences and personal growth, and those who are committed to the process can do it, whether by simple choice or as an aspect of identity.
Monogamy creates for many a desired sense of security. Becoming good at polyamory almost always requires giving that up in order to stretch, grow and challenge internalized cultural messaging. Failing to do this as to what is and is not ethically and morally acceptable is not an option if we are to reach a safe and secure comfort level with sharing with others our loved one's heart, time and attention. A fair number of people find that the transition is more difficult than they imagined and tend to be those for whom a poly life is a choice. They don't have that sense of identity that others find the need to fulfill. No problem!
"... or is it something some people are."
Yes. Or at least it is for many of us. You've heard from quite a few people who feel a strong sense that this is exactly who they are. It seems that like so many debates about complicated, emotionally charged subjects, the answers are not found in the black or the white but are instead found in the gray area. Some of us are doing it because we like it but could live without it in order to gain something else of value. Others can't imagine being any other way and make sure to choose partners who share their perspective.
Thanks for discussing this and for considering all the feedback.
Anita Wagner Illig