Yet while nothing can be more evident than that certain characteristics of growing boys and girls, both physical and mental, are the result of a direct inheritance from the past, it is equally evident that certain others are not. In certain conspicuous traits, our children favor their long-departed ancestors; but in certain others they are even less like them than we. Our anthropoid ancestry were hairy; children are less hairy than adults. We have larger brains and shorter arms than our forebears, but our children have still larger brains, relatively, and still shorter arms than we. In a dozen different ways, the older a man grows, the more, not the less, apelike does he become; as, for example, in the curve of his back and the great bony ridges over his eyes. In these respects, the child looks rather to the future than to the past. The child, indeed, recapitulates the history of the race, but only so far as it is some real advantage to him to do so, and never merely for the sake of recapitulating. When Nature cannot utilize an ancestral quality here and now, out it goes, to make room for something wholly new. Certain qualities of youth, then, are an inheritance from the past; they exist because of the men and women that were. Certain others are a prophecy of adult life, and exist because of the men and women who are to be. Most of our youthful characteristics are simultaneously of both these sorts. They have persisted from an immemorial past; but they have persisted, instead of being lost by the way, because they have proved themselves useful in this present. Thus, for example, we recapitulate a gill-slit stage, because we actually did have a fish ancestor; but we use these gill-slits, not to become adult fish, but as a convenient device for building an aortic arch such as no fish ever had. We are tailed embryos as a step in becoming tailless men; and in the same way, we are boy savages as a stage toward becoming civilized human beings. The savage impulses of a long departed past appear in every modern boy, both because they are an inheritance from that past and because they are a preparation for the boy’s future. We tend to recapitulate only so much of the ancestral experience as we can actually use.