Anaximander

A younger associate of Thales, Anaximander refused to ground the world in any single element. Water, air, fire are all limited, and what limits cannot be the source of everything. So he proposed the apeiron, the boundless, an indefinite stuff from which all opposites separate out and into which they return. He drew the first map of the known world, built a sundial, and argued that the earth floats unsupported at the center of things, held by nothing because it has no reason to fall one way rather than another. He even guessed that humans must have descended from other animals, since a human infant could never have survived alone.