In chapter 5, "Anaximander of Miletus," of his book Philosophy Before Socrates, Richard D. McKirahan suggests in a couple of paragraphs that the presocratic philosopher Anaximander can be seen as the father of the theory of evolution:
Particularly striking is Anaximander’s recognition and solution of a problem arising from the helplessness of human infants. The first humans could not have come into this world as babies or they would have died before reaching an age at which they could propagate the race. How, then, did they come into being? This “first generation problem” can be answered by positing a god who creates adult humans or by asserting that the world and the human race have always been in existence. However, both these solutions conflict with basic features of Anaximander’s system. Accordingly he takes an original and ingenious approach, having the first humans nurture in other animals until self-sustaining.
For his claims that animals arose in the sea before they emerged to live on dry land and that they developed from fish, and for recognizing the need for a different original form for humans and the difficulties of adapting to different habitats (perhaps implicit in the short lives of the animals who first moved onto dry land), Anaximander is sometimes called the father of evolution. This interpretation is wrong, however, since he says nothing about the evolution of species. His problem of how to account for the first generation of each kind of animal, how to get each kind of animal established once and for all, is different from Darwin’s. Moreover, he makes not mention of such Darwinian mechanisms as natural selection.Anaximander was the student of Thales and the teacher of Anaximenes—it is possible that Pythagoras too was one of his students. Anaximander’s comprehensive and systematic ideas had a seminal impact on the Greek thinkers (including Plato and Aristotle) who followed him. In Raphael’s painting The School of Athens, Anaximander is represented leaning towards Pythagoras on his left.