It's implied, through the superpower statuses of both Gondawa and Enisorai, that there've been civilizations before the modern day and historical ones. Given that there have been civilizations before the industrial one (think of the Ancient Egyptian or the Greek-Roman ones, or especially the Mesopotamia ones for example) but none before 3500 years BC (without counting the In-Universe examples mentioned below), that basically means that prehistoric members of the Homos sapiens species, and their modern day descendants, have been the postapocalyptic descendants of the survivorsof the cultures that have been erased because of the Enisorai - Gondawa war all along.
