water-dwelling humans appeared as fishes in the sea, and came out upon the land only when they had so far developed that they were able to live in the air. The capsule-like case which enclosed their bodies then burst, freeing them and allowing them to reproduce their kind upon the continents. In his ideas of the origin of life Anaximander was the pioneer of "Abiogenesis," teaching that eels, frogs, and other aquatic creatures were directly produced from lifeless matter.
Anaximander's pupil, Anaximenes, departed radically from the teachings of Thales. He thought that air, not water, was the cause of all things, yet he held that in the beginning all creatures were formed from a primordial slime of earth and water. Another pupil of Anaximander, Xenophanes (576–480), made himself famous by discovering the true nature of fossils. Before his time, and indeed, for thousands of years afterward, fossils were held to be accidents, or natural growths, or creations of a devil, or of a god who delighted in puzzling his earthly children. Xenophanes. rightly interpreted them to be the remains of animals, and from this concluded that seas formerly covered what is now dry land.
Empedocles, (495–435) taught what is probably the first clearly formulated theory of evolution. He supposed that many parts of animals, such as heads, legs, necks, eyes, ears, and so on, were formed separately, and were kept apart by the mysterious forces of hate. But love of part for part finally overcame the
