Man has evolved from creatures that went on all fours and lived in trees, and in consequence of his upright posture and changed habits of life, some structures which are active in the apes are rudimentary in the human body. A shoulder muscle that is a source of strength to the apes in climbing, lingers in man as a mere fibrous remnant that has dwindled through disuse. Another muscle which runs through the wrist into the palm of the hand, another which extends from the calf of the leg to the sole of the foot, another which passes from the shoulder to the neck and was once used to lift the collar bone—these muscles, which are well developed in the true apes, and less developed in the anthropoids, are rudimentary in man. These rudimentary organs and muscles are links in the chain of man’s descent and they point unerringly to the source of his origin. The long heel and the poorly developed calf of the anthropoid ape remind us that he has but recently, so to speak, acquired the upright posture. In the negroid races also the long heel and diminutive calf are notable characteristics; while in the white and yellow races the heel is short and the calf well formed and muscular. Once more, the obvious conclusion is that the black man’s long heel and slender calf represent a more primitive development; while the leg and heel of the white man and the Mongolian show the work of evolution farther advanced. [Illustration: FIG. 39.—THE RUDIMENTARY MUSCLES OF THE EAR.] Three months before birth, the human babe is covered with a luxuriant growth of soft, brown hair, called the “lanugo,” precisely the same as the ape baby. And throughout life the body of every human being is covered with a rudimentary growth of hair. But this it not all. It is as suggestive as it is interesting that in man and in the anthropoid apes the hair on the upper arm and the hair on the lower arm always grows towards the elbow (Fig. 40)—a phenomenon which occurs nowhere else in the animal world except in a few American monkeys. In a primitive Australian race, the Ainos of Japan, and the pygmies of the Upper Nile, the extreme hairiness of the body is a notable characteristic. And the photograph of Julia Pastrana, a Siamese (Fig. 41), shows that this lady was not only bearded like a man, but that her entire body was plentifully clothed with hair. Some chimpanzees, on the other hand, are remarkably hairless. One variety is, in fact, almost entirely bald.