The problem is that if these hypothetical civilizations existed , they left no physical trace while the many groups of anatomically modern homo sapiens , homo sapiens neanderthalensis , homo sapiens denisova , homo sapiens nadeli to name only a few of the many different kinds of homos that have existed in the last 200 k years somehow managed to leave many traces while practicing a minimalist huntergatherer lifestyle . You would think and actually we know that statelevel societies would leave much more evidence than would huntergatherer societies , but while we find ample evidence of 200 k year old huntergatherer societies , we have absolutely zero evidence of 200 k year old statelevel societies . The simplest explanation for the observed evidence is that statelevel societies did not begin to exist until well after anatomically modern humans had killed off or nearly killed off all other forms of homo , had killed off most forms of megafauna though not in Africa where the fauna had evolved alongside walking apes and was therefore much more resilient , and had survived the most recent iceage , the end of which , in rough terms , just happens to coincide with the advent of agriculture in the near east .