The World Before The Flood

Although various ancient traditions refer to a lost antediluvian world, the one that stands out is the tradition in the first chapters of Genesis, because of its geographical detail, its monotheism (which predates polytheism) and its historical rather than epic style. These chapters describe a world very different from our own. Either the world really was different at Creation or, looking back, a later pre-scientific culture speculated about it in error. If the former, what source of information might they have drawn upon?