Arguably humans were not made for realations with only one other person. Look around the animal kingdom, few if any have this social construct.
Humans aren't that animals you think. Humans were created to have a soul and spirit being like God. That's what the Bible talks about at the creation of Adam - to make man in the likeness of God. I think the issue of divorce is mostly man's crave for satisfaction at every little frustration. That of the Gates takes the crown and beggars disbelief.