The science of life : fully illustrated in tone and line and including many diagrams

THE EVOLUTION OF MAN

may still evade us, we have enough of the branches to feel assured it is there. Every extinct species of man is in one way or another more ape-like and less human than any living race of men ; in Pithecanthropus and Sinanthropus we have true linking forms between men and apes, only slightly, if at all, on the human side, while in Dryopithecus we have a true ape, some of whose characteristics are more human than those of any modern apes—a pier from the apeward end of the bridge from not-man to man.

The evidence therefore is clear not only that man is closely akin to the apes, but that he is actually descended from an animal which, though without doubt different from any living gorilla, chimpanzee, orangoutang, or gibbon, would obviously have to be classified as an ape, which was covered with hair, provided with formidable teeth, had a brain not above half the size of ours, and spent most of its life on the ground or among the branches in the still prevalent but dwindling forests of the Pliocene.

§ 3 Man’s Body: a Museum of Evolution

Man’s likeness to the apes shows us clearly enough in what direction to look for his evolutionary origin. But the proof that he has had an evolutionary origin and was not specially created—that rests on a much larger mass of evidence. Our adult human bodies are among the best proofs of Evolution ; and the private development of each one of us is an affidavit swearing to the evolutionary history of our race.

Wiedersheim, the celebrated German anatomist, enumerated in the body of man no less than one hundred and eighty organs which are vestigial—wholly or almost useless to us, though useful in other species of animals—each one of them a stumblingblock to the believer in special creation but an ally to the Evolutionist. We may note one or two examples.

The body-hair of men and women is purely vestigial; it no longer serves to prevent us losing heat. And yet each of these tens of thousands of useless hairs possesses a useless muscle by means of which it can be, quite uselessly, raised. For a furry creature to bristle up its hair when the weather grows cold is useful enough—more air is entangled in its coat, and it loses less heat. In the same circumstances we also erect our futile little hairs; but the resultant goose-flesh condition is of no value whatever

—we have performed a vestigial action. Even the arrangement of the hairs on our body may recall the past. The hairs on our upper arms point downwards; those on our forearms run upwards and outwards to our elbow ; precisely the same arrangement occurs in the orang-outang, and it has plausibly been suggested that in this animal, which often sits with its arms clasped over its head, the arrangement may serve to shed rain off the body, down the spouts of long hair projecting at the elbow. But whatever its significance in the apes, its existence in man is yet another proof of their kinship to him.

A few talented human beings can move their ears. Apart from being a minor social accomplishment this has no value ; but for a wild creature, like a rabbit or a zebra, whose safety.may depend upon its power of detecting faint sounds and the direction from which they come, the power of moving its ear-trumpets is vitally important. The human ear-mover is indulging in a vestigial action, but the ears of the rest of humanity are one step more vestigial, for the power of moving them has been lost. In spite of this, however, a whole set of muscles to move them is still present, though never called upon for action, since for some reason we are not able to control them. This, by the way, is also true of the great apes, which, like us, have useless vestigial ear-muscles. In tailed monkeys, on the other hand, the muscles are large and can be used, although they are not as strong or supple as those of, say, a dog. |

Another interesting vestige in the ear 1s a little conical projection from the inturned margin of the ear, usually called “ Darwin's point,” since he showed that it was the remains of the tip of the pointed ear of lower forms, now folded downwards and inwards. It is only found in a certain proportion of human beings (and, curiously enough, is stated to occur more often in men than women) ; but when present 1t 1s, as Darwin wrote, ‘“‘ a surviving symbol of the stirring times and dangerous days of his animal youth.” ;

Again, the little fleshy fold in the inner angle of our eyes (between the openings of the tear-duct in Figure 48) seems to have no function whatsoever; but in most lower vertebrates, including many mammals such as the cats, this same fold is a veritable third eyelid, which can be rapidly swept ae the eye from one side to _the other. Re further proof of man’s simian relationship it may be noted that apes and monkeys,

253