What is "Literature" and "Civilization?"

I'm sure lots of people have lots of different ideas as to what literature is. I instantly think of Shakespeare, Marlowe, Fitzgerald, and Rowling. Others may think of endless assignments and sonnets with little to no meaning to them.
What exactly does civilization mean? I think back to the Dark Ages and beyond, when the dollar and the internet didn't exist (gasp!).
After asking three people what they thought these words meant, I have a better grasp on the definitions too.

Morgan Vienneau
Literature: "Written works that express language."
Civilization: "A group of living people."

Sarah Posz
Literature: "A group or body of writings about a common theme."
Civilization: "Groups of people colonized in one place who share a common goal."

Courtney Bogert
Literature: "Mark Twain, and something I don't like."
Civilization: "A community built on principles shared by the majority of its citizens."

It seems that everyone has a grasp on the fact that literature has to do with writing and that civilizations have to do with people, but beyond that strict definitions become moot because these words can mean different things to anyone.