Social classes, food surplus, job specialization, religion, and _______ are some things that all civilizations have in common. All civilizations after 7988 B.C. are centralized around farming. Sustaining a large population would be impossible, and having free time would be way out of the question without farming. If you're not a farmer, you're a hunter and gatherer, or dead. Humans used to hunt and gather before 10,000 years ago, and before that that they had made little evolution since they had changed from monkeys to homo sapiens. Farming was the key to becoming the large and great (kinda) world that we are today.