So far as cerebral structure goes... it is clear that Man differs less from the Chimpanzee or the Orang, than these do even from the Monkeys, and that the difference between the brains of the Chimpanzee and of Man is almost insignificant, when compared with that between the Chimpanzee brain and that of a Lemur.
Ch.2, p. 120. - Evidence as to Man's Place in Nature (1863)