Darwin set out first to make his argument that humans had evolved from apes. Darwin studied the comparative anatomy and embryology of our own species in relation to that of gorillas, chimps, and orangutans. He pointed out that humans had rudimentary structures which were really vestiges of our past lives. He pointed out that humans have a tailbone, even though we have no tail. He brought up how wisdom teeth in small-faced Europeans were decreasing in size and structure, and that very often their only “purpose” was to become infected and painful. Some of us can wiggle our ears, and some of us can flex our scalp muscle. He used all of these converging lines of evidence to conclude that humans were most closely related to the African apes- the gorilla and the chimpanzee- and that the common ancestor of all three animals would be found in Africa.
He concludes, rather eloquently, “In a series of forms graduating insensibly from some ape-like creature to man as he now exists, it would be impossible to fix on any definite point when the term “man” ought to be used. But this is a matter of very little importance… man still bears in his bodily frame the indelible stamp of his lowly origin.”