it is not easy to realize that it was only a single generation ago when we used to think that the animals are ruled by instinct, man by reason. we know better now. what was once the “new” psychology has taught us that man has more separate instincts than any other creature that breathes, and that however superior his rational life, it is still based upon a substructure of primitive instincts which he shares with the beasts of the field.

the newborn infant feels on his skin the air of a cold world, and sucks in his first breath without knowing how or why. he manages, the first time he tries, about as well as he ever will, the decidedly complex operation of taking breath and food at the same time, crossing the two streams in his73 throat, and sending each to its proper destination without confusion with the other. when the proper time comes, the child who has gone on all fours like an animal gets up on his hind legs to walk like a man.

we are all of us, therefore, man and animals alike, born with the particular set of instincts which prompt us, without our taking thought, to whatever acts are essential to our physical life. some of these instincts are active at birth; more lie dormant, to ripen and manifest themselves only at the proper age, each in its proper time. the impulse to walk and to utter words comes suddenly, in babyhood. the mating instincts appear only toward the end of adolescence. metchnikoff will have it that at the end of a well-spent life, an instinctive longing for death replaces the will to live.

the physical differences between boys and girls are strikingly correlated with a difference in instinctive interests. brought up alike, in a hundred little ways they are dissimilar. i have seen at a children’s party, on the advent of a baby, every little girl74 leave the supper table to surround the new-comer, while every little boy kept on with his meal. where the girl plays with dolls, the boy plays with bats and balls.

among other divergences, the boy forms gangs. girls do not form gangs. they belong to sets, and sets and gangs are quite different institutions. the set is exclusive, undemocratic. it has no organization, leaders, history, and it owns no property. the set snubs its rivals; the gang fights them. the members of a set also snub one another, quarrel, and backbite. there is none of the deep-seated, instinctive loyalty which the members of a gang have for each other. the normal boy may fight his friend; he does not “get mad at” him.

all this is only one aspect of the deep-seated difference between “the only two kinds of people there are in the world, men and women.” barring dolls and the ability to hurl missiles, little girls and little boys, as they emerge from babyhood, are not so very unlike. but somewhere about the age of ten, the little boy begins to undergo a75 transformation, which in the girl never takes place at all. he begins to develop the gang-forming instinct. he begins to want to do things which he cannot do at all alone; and cannot, moreover, do with any real satisfaction except in conjunction with a special group of his fellows. the once friendly boy becomes shy of adults, so that only the rare man or woman can retain his full confidence. girls he scorns. his games tend now to be of the co?perative type, in which there is a definitely organized side, with a leader and more or less specialized functions among the players, and where one side wins or loses to the other as a whole. it is no longer each for himself, but each for the team. a girl can be taught to like this kind of game; a boy takes to it like a duck to water.

apparently, then, a boy joins a gang and a girl does not for precisely the same reason that he throws stones while his sister tends lovingly the dolls that are beneath his contempt. each is doing instinctively, as a child, for play, what grown men and women have been doing these thousand years for work.

76 for obviously the instinctive activities of the boys’ gang are the necessary duties of the savage man. the civilized boy hunts, fishes, fights, builds huts in the woods, stands loyally by his fellows, and treats all outsiders with suspicion or cruelty, and in general lives the life and thinks the thoughts of the savage man. he is, for the moment, a savage; and he instinctively “plays indians” as the real savage lives them.

general opinion has it that the boy instinctively plays indians and follows the so-called tribal occupations as the direct result of his inheritance from some thousands of generations of savage ancestors who, willy nilly, have been doing these things all their lives. we commonly believe that the normal boy is possessed to throw stones at every moving object because his forebears got their livings or preserved their lives by throwing all sorts of missiles at prey and enemies, so that the fascination of sticks and clubs is but the reverberation of the not so very far off days when sticks and clubs were man’s only weapons.

77 according to this doctrine, such a game as baseball is an epitome of man’s prehistoric activities. to throw accurately and to run swiftly, to hit a quick-moving object with a club, is to revive, symbolically, the most absorbing of ancestral activities and the most vivid of ancestral memories. as the girl, tending her doll, is recapitulating the experiences of a hundred thousand mothers before her, so the boy, in the varied activities of his gang, is reproducing the life of long departed clans and tribes. the instinctive interests of both boys and girls are the result of the experiences of their ancestors.

all this, one need not point out, is the familiar recapitulation theory, the doctrine, that is to say, that the young of each species, our own included, tends to reproduce in the course of its youth the successive stages in the history of its ancestors. we are by turns invertebrates, gill-breathing vertebrates, lung-breathing vertebrates (we make the great change at birth), little monkeys, little savages, and finally civilized men and women.

it is an illuminating theory, and one, moreover,78 which goes far toward explaining many aspects of our human nature which without it would be largely meaningless. especially is it the key to the behavior of boys at the gang age. the normal boy between ten and sixteen is really living through the historic period which, for the races of northern europe, began somewhere this side of the glacial period, and came to an end with, let us say, the early middle ages. he is, therefore, essentially a savage, with the interests of a savage, the body of a savage, and to no small extent, the soul of one. he thinks and feels like a savage; he has the savage virtues and the savage vices; and the gang is his tribe.

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 were79 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; but80 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.

conversely, what we keep is useful; or else has been useful so very lately that we have not had time to change. before the days of gunpowder—and how short a while, after all, that was—handling spear and javelin was a matter of life and death. then, as now, boys had the missile-throwing instinct,81 and girls did not. they had it, on the one hand, because their ancestors had been spear-men; but they had it, on the other hand, and equally, and long before they were old enough to fight, in order that they might enjoy the long continued practice that taught them to throw well. evidently, a spear-fighting people whose boys lacked the throwing instinct, so that they had to be coerced into doing their spear practice, would soon go down before a rival group whose boys found spear throwing a spontaneous play. in the same way, the children of girls who did not love dolls and pets and all small and helpless things could never, even under modern conditions, make head against the children of girls who did. all the peoples whose women tended their babies from a sense of duty have long ago gone to the wall.

the woman must tend her babies; therefore the girl loves dolls. the man, to be a member of any human society, whether civilized or savage, must stand by his fellows, follow his leader, act with his associates, be82 loyal to the death. therefore the boy has the gang-forming instincts. these are, in a real sense, an inheritance from the past, but they are in an equally real sense a gift of the present to the future. boys and girls alike repeat so much of their common ancestral experience as helps to make them efficient men and women, and no more. if there were no such thing as heredity, if each generation simply sat down and created the next to suit itself, we should still have to make the girls love dolls and the boys form gangs. without these instincts, neither girls nor boys would become fully equipped adults.