Have you ever been in class or lecture, at a nature reserve, reading a book, or even simply been talking to someone who knows a bit about animals and been told that whatever animal mates for life? If you look around at the others around you (and I bet you do it too) they will get that goofy knowing look on their face or say something about it being cute or even romantic. We feel more of a connection to the animal they go up a knotch in our mind. We see mating for life as a sign of higher development.
Whether you believe in Creation, Evolution, that the aliens plated us, or even in that flying pasta monster I think most people will agree that humans are probably the highest of creatures. Some feel we are created in the image of God, the highest evolved, descended from the aliens or whatever. But most everyone feels that humans are the most intelligent individuals with quite the sense of socitey and community.