Page:Popular Science Monthly Volume 46.djvu/387

Rh by a four-footed mode of progression. The attainment of the upright body-position of man tends during the course of his life to reduce prognathism—an adult is far less prognathous than when a baby; and it has tended during phyletic development to the same end—the European, the more developed form, is less prognathous than the negro. Reduction of prognathism leads to a better carriage of the head, because the weight is borne nearer the perpendicular, which is economy. Economy, it may be remarked, is most important to the man whose expenditure and income are too nearly on a par; and this dictum of necessity applies to civilized man, whose income in the shape of physical and nervous energy is much less, and his expenditure far greater, than that of the savage. But there are other factors at work: the civilized man requires the enlargement of the frontal capacity of his skull, and material saved in jaw-making can be utilized in skull-enlargement. Then there is the lessened use of teeth and jaws in mastication, and therefore a smaller demand upon those organs: these and other causes all work to the same end—a reduction of prognathism. If any one will draw to the same size the facial profile of a cat, a monkey, a baby, and an adult man, he will have represented four stages in the reduction of prognathism, and he will begin to understand to what the prognathous baby points. He will learn that in a designed biped the heavy jaw is a piece of faulty construction reflecting no credit on an artificer, whereas it is a necessary accompaniment of a biped developed from a quadrumanous or quadrupedal animal, imperfectly, incompletely, and gradually adapting himself to the bipedal position.

Attention may be called to another feature pointing out the same lesson of alteration and imperfect adaptation. Below the nose runs a furrow parting the ui)per lip. In the faces of babies and children this furrow is very noticeable: from the evolutionist's point of view. it is one of the most remarkable characters of the face. It tends to become obsolete in old age, and it is not seen among the catarrhine monkeys. Among the platyrrhines it is but feebly developed; but in lemurs it is in a more pronounced state—there is a depressed septum to which the two side pieces are joined—the upper lip, in fact, is nearly split in two, but held together by a depressed piece of flesh. In the Marsupialia and Rodentia the lip is practically in two pieces, and each piece is capable of being moved separately. This is the "harelip"; and its method of use may well be noticed in a hare or a rabbit when eating. The furrow, therefore, in a child's lip points to this: that our ancestors possessed, not a single upper lip, as we do now, but two upper lips, one beneath each nostril, both capable of independent movement. In course of time these two lips have, owing