From this point Greek rationalism is continuous, despite reactions, till the Roman conquest, Miletos figuring long as a general source of skepticism. Anaximandros (610-547 B.C.), pupil and companion of Thales, was like him an astronomer, geographer, and physicist, seeking for a first principle (for which he may or may not have invented the name [482]); rejecting the idea of a single primordial element such as water; affirming an infinite material cause, without beginning and indestructible, [483] with an infinite number of worlds; and--still showing the Chaldean impulse--speculating remarkably on the descent of man from something aquatic, as well as on the form and motion of the earth (figured by him as a cylinder [484]), the nature and motions of the solar system, and thunder and lightning. [485] It seems doubtful whether, as affirmed by Eudemus, he taught the doctrine of the earth's motion; but that this doctrine was derived from the Babylonian schools of astronomy is so probable that it may have been accepted in Miletos in his day. Only by inferring a prior scientific development of remarkable energy can we explain the striking force of the sayings of Anaximandros which have come down to us. His doctrine of evolution stands out for us to-day like the fragment of a great ruin, hinting obscurely of a line of active thinkers. The thesis that man must have descended from a different species because, "while other animals quickly found food for themselves, man alone requires a long period of suckling: had he been originally such as he is now, he could never have survived," is a quite masterly anticipation of modern evolutionary science. We are left asking, how came an early Ionian Greek to think thus, outgoing the assimilative power of the later age of Aristotle? Only a long scientific evolution can readily account for it; and only in the Mesopotamian world could such an evolution have taken place. [486]