The Mesoamerican and South American civilizations - Aztecs, Mayans, Incas - ruled vast areas, set up complex, well-ordered states and constructed impressive cities and monuments. And yet, strictly speaking, they were Stone Age cultures: they had no metal tools or weapons (gold and silver working was known, but for ornamental use only) and except for the Mayans, briefly, they had no systems of writing.
Others have explained how these empires existed without theses supposedly crucial elements. My question is this - why were there no equivalent cultures in the Old World? The earliest civilization I know of, the Sumerians, had both bronze and writing, as did later Eurasian cultures. Were there, in fact, massive empires I am unfamiliar with that made do with stone tools? Or did civilization simply evolve differently in the east?