Re: Human Beings are not supposed to be monogamous...
Human Beings have no "nature". We are not poly / monogamous. We have accepted "monogamous" structure because that what works best for us (especially in the old times).
"nature" of any living being - CANNOT be changed. For example, A lion nature is to eat meat. It will die of starvation but will not eat any veges. Duck when hatched know how to swim, how their predators are - and look to get into water to avoid predators , that is their nature.
Human "learn" as they grow and adapt to their surrounding.
(we can find few exceptions to refute this claim for humans, but in general - humans don't have NATURE )