Extraordinary new discoveries suggest that civilization as we know it began 12,000 years ago. Between the Middle Eastern rivers of Tigris and Euphrates, the world's first cities, Ur and Babylon, were built out of mudbrick and grew into vast empires. See how recent excavations are rewriting the first chapter in man's long journey to civilization. Then track how these ancient societies expanded to Africa, Europe, and ultimately became inexorably linked with the Western world, thanks, in large part, to the conquests of Alexander the Great.