I'm not someone who would say "humans weren't made for monogamy", no - because I don't think you can make a sweeping statement and apply it to the whole of the human race, past, present and future with no exceptions.
In the same way I wouldn't say "humans were made for monogamy" either.
I am happy to accept that polyamory isn't for everyone. But it works for me. It works for my partner. It works for her other partner. And to an extent it works for the other people who we (individually) occasionally sleep with, who may not in themselves be polyamorous but are accepting of our polyamorous relationship status and therefore understand that by sleeping with - for instance - me, they are not doing any wrong to my partner.
@ Thucy: "i know myself that if i loved a girl i wouldnt be able to stand the thought of her giving it up to someone else. it begs the question - what does he have i dont? and it works both ways - this isnt some kind of male possession complex."
Indeed it is true that jealousy affects both men and women. And while it isn't specifically a male complex, your response is somewhat possessive...
In terms of "what does he have that I don't?", my response is to recognise that however great a person you might be, no-one can be perfect, no-one can be everything. There will always be someone who is better than you at one thing, even though you might be better than him at other things. So it's almost inevitable that there *will* be another guy who *does* have something you don't. You have something he doesn't, too. Every person is different to the next, and variety is the spice of life!
Maybe there's another guy your partner likes. Maybe you're more handsome and better in bed than he is, but maybe he's a better cook and his jokes are funnier. He 'clicks' with your partner about as well as you do, she likes spending time with him and she would probably like to express her joy in his company by sleeping with him once in a while, if you didn't object to this.
There are two potential ways you can respond to this scenario:
1. The normal response: You feel jealous of this other guy. You tell your partner you feel uncomfortable about how close she's getting to him. You ask her to promise not to get too involved with him. You reassure her that you only feel this jealousy because of how much you love her. She says she understands - but you continue to keep a careful eye on them just in case.
2. The compersive, polyamorous response: You are pleased that your partner has found someone whose company brings her joy. Spending time with this guy makes her happy, and because you care deeply for her, the fact that she is happy is pleasing to you, too. You allow them to spend some time together, including some time alone, as long as your partner remembers to make plenty of time to spend with you too. You can use the time your partner isn't with you to enjoy other things that she's less interested in - or the company of other friends, romantically or otherwise.
That's how it works for me anyway. The other guy *does* have something I don't, and allowing him to enrich my partner's life is a positive for me, too, because she is happy.