We have to face the fact that we are the descendants of apelike ancestors. The truth, at first sight, is often ugly and repulsive to our personal feelings, but when it is the truth, its ultimate effects on us are always salutary. ... ... Man's brain does not stand as a thing apart; it is the culmination of an ascending series. There is no part of it and no function manifested by it that cannot be traced to humble beginnings lower in the animal scale. And what we postulate for man's brain we must in all justice apply to that of the ape, the dog, and all other beasts.
— ARTHUR KEITH