Hmmm...well...if monogamy equals codependency for YOU, kinetic, then yeah, it's probably not healthy. Definition check, eh? I think you need to reevaluate and give a nod to meninlove for his reference to interdependence. Both said, your view will be determinant of how 'healthy' your relationship is, regardless of label.
Meanwhile, let me laugh you, Webster666, off the face of the planet. Monogamy against our nature? So, let me get this 'straight'...you find that you are a product of your reptilian brain and the bulk of that other gray matter is, uh, doing what for you? Personally, I don't find the comparison to the animal kingdom at large relevant as a more complex brain and higher cognitive functioning does equal, at very LEAST, a choice in our actions. Sure, maybe there's an evolutionary relevance to spreading your seed, as it were, but for your argument to be based in this 'mindless' reference is laughable at best and discounts, or not, what's between your ears.
That said, if monogamy works for you...great...if not, great also! I lend myself to the former ideology but don't particularly worry about what others do, you know? Just don't promote stupidity in promoting your thoughts, eh?
LOL kudos to lilTanker.