Why should not nature work, not for the sake of something, nor because it is better so, but just as the sky rains–not in order to make the corn grow–but of necessity? What is drawn up must cool, and what has been cooled must become water and descend, the result of this being that the corn grows. Similarly if a man’s crop is spoiled on the threshing-floor, the rain did not fall for the sake of this–in order that the crop might be spoiled–but that result just followed.
Why then should it not be the same with parts of the body in nature? Our teeth, for example, come up by necessity–the front teeth sharp, fitted for tearing, the molars broad and useful for grinding down the food–since they did not arise for this end, but it was merely a coincident result; and so with all other parts in which there appears to exist a purpose. Wherever then all the parts came about just as if they had come be for a certain purpose, such things survived, being organized spontaneously; whereas those which grew otherwise perished and will always perish.
Thousands of years later Charles Darwin read this passage and immediately recognized this as his conception of natural selection. He comments in On the Origin of Species that “we here see the principle of natural selection shadowed forth.” Unfortunately, Darwin adds, “how little Aristotle fully comprehended the principle is shown by his remarks on the formation of the teeth.”
Aristotle rejected this evolutionary view since as he writes, “teeth and all other natural things either invariably or normally come about in a given way; but of not one of the results of chance or spontaneity is this true.” Rather, Aristotle endorsed a “teleological”–or end-based/purpose-driven–view of the universe. He writes that “where a series has a completion, all the preceding steps are for the sake of that” and that to assert that life “must have come to be at random… does away with ‘nature’ and what exists ‘by nature’… [since] when an event takes place always or for the most part, it is not incidental or by chance.”
Thomas Aquinas–whose views dominated the West for many hundreds of years–adds to Aristotle’s rejection of evolution, writing that “it must also be noted that the growth and conservation of growing things on earth occur in most cases because of the rain, whereas their corruption occurs in few instances. Hence although rain is not for their destruction, it does not follow that it is not for their preservation and growth.”
Aristotle had other problems with the idea of evolution as well. He saw all life as part of a Great Chain of Being, a hierarchy which placed humanity at the top and everything else on lower levels of the Great Chain. This static perspective on species allowed no room for evolutionary thought. The Great Chain was perfect and immutable.
The “Great Chain” view is completely antithetical to the idea of evolution. Evolution doesn’t produce a hierarchy. Human beings are not “more evolved” than other apes. We’re just different. Evolution isn’t about progress–it’s about diversity. Apes and humans are just two different end points on the tree of life, not higher or lower points on a ladder.