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 activit............