Civilizations did not "appear at the same time" so much as persist throughout our knowledge of history and prehistory. Civilization is a great way to organize our species in many situations, and we have always taken advantage of that. read more
Homo Sapiens had appeared and populated Africa, Europe, Asia and Australia by 50,000 BC, and the Americas by 12,000 BC (perhaps much earlier). After that not much happens for tens of thousands of years. read more