That the human ear was not always the squat and degenerate instrument it is at present may be seen by a critical glance at its structure. Mr. Darwin records how a celebrated sculptor called his attention to a little peculiarity in the external ear, which he had often noticed both in men and women. “The peculiarity consists in a little blunt point, projecting from the inwardly folded margin or helix. When present, it is developed at birth, and according to Professor Ludwig Meyer, more frequently in man than in woman. The helix obviously consists of the extreme margin of the ear folded inwards; and the folding appears to be in some manner connected with the whole external ear being permanently pressed backwards. In many monkeys who do not stand high in the order, as baboons and some species of macacus, the upper portion of the ear is slightly pointed, and the margin is not at all folded inwards; but if the margin were to be thus folded, a slight point would necessarily project towards the centre.”[5]
Here then, in this discovery of the lost tip of the ancestral ear, is further and visible advertisement of man’s Descent, a surviving symbol of the stirring times and dangerous days of his animal youth. It is difficult to imagine any other theory than that of Descent which could account for all these facts. That evolution should leave such clues lying about is at least an instance of its candor.
HORNED SHEEP AND GOAT WITH CERVICAL AURICLES.—FROM “EVOLUTION AND DISEASE,” J. BLAND-SUTTON.
But this does not exhaust the betrayals of this most confiding organ. If we turn from the outward ear to the muscular apparatus for working it, fresh traces of its animal career are brought to light. The erection of the ear, in order to catch sound better, is 56 a power possessed by almost all mammals, and the attached muscles are large and greatly developed in all but domesticated forms. This same apparatus, though he makes no use of it whatever, is still attached to the ears of Man. It is so long since he relied on the warnings of hearing, that by a well-known law the muscles have fallen into disuse and atrophied. In many cases, however, the power of twitching the ear is not wholly lost, and every school-boy can point to some one in his class who retains the capacity and is apt to revive it in irrelevant circumstances.
One might run over all the other organs of the human body and show their affinities with animal structures and an animal past. The twitching of the ear, for instance, suggests another obsolete or obsolescent power—the power, or rather the set of powers, for twitching the skin, especially the skin of the scalp and forehead by which we raise the eyebrows. Sub-cutaneous muscles for shaking off flies from the skin, or for erecting the hair of the scalp, are common among quadrupeds, and these are represented in the human subject by the still functioning muscles of the forehead, and occasionally of the head itself. Everyone has met persons who possess the power of moving the whole scalp to and fro, and the muscular apparatus for effecting it is identical with what is normally found in some of the Quadrumana.
Another typical vestigial structure is the plica semi-lunaris, the remnant of the nictitating membrane characteristic of nearly the whole vertebrate sub-kingdom. This membrane is a semi-transparent curtain which can be drawn rapidly across the external surface of the eye for the purpose of sweeping it clean. In birds it is extremely common, but it also exists in fish, mammals, and all the other vertebrates. Where it is not found of any functional value it is almost always represented by vestiges of some kind. In Man all that is left of it is a little piece of the curtain draped at the side of the eye.
When one passes from the head to the other extremity of the human body one comes upon a somewhat unexpected but very pronounced characteristic—the relic of the tail, and not only of the tail, but of muscles 57 for wagging it. Everyone who first sees a human skeleton is amazed at this discovery. At the end of the vertebral column, curling faintly outward in suggestive fashion, are three, four, and occasionally five vertebræ forming the coccyx, a true rudimentary tail. In the adult this is always concealed beneath the skin, but in the embryo, both in man and ape, at an early stage it is much longer than the limbs. What is decisive as to its true nature, however, is that even in the embryo of man the muscles for wagging it are still found. In the grown-up human being these muscles are represented by bands of fibrous tissue, but cases are known where the actual muscles persist through life. That a distinct external tail should not be still found in Man may seem disappointing to the evolutionist. But the want of a tail argues more for the theory of Evolution than its presence would have done. It would have been contrary to the Theory of Descent had he possessed a longer tail. For all the anthropoids most allied to Man have long since also parted with theirs.