From what has just been said it will be clear that we shall have to consider the history of laughter and the movement of social evolution as inter-connected. Not only does a change in ideas, sentiments or institutions tend to modify the expression of the mirthful mood, there is a reciprocal influence of laughter upon ideas, sentiments and institutions. Such interaction holds good generally between amusements and serious pursuits; the recreations of a community serve in important ways to determine the measure of the vigour thrown into serious activities. In the case of laughter this reciprocal influence is much more marked, owing to the circumstance that mirth has been wont to play about serious things, to make these the target for its finely tipped shafts, now and again going so far as to shoot one into the midst of the solemnities of social life. In the savage tribe we find but little of class division. The perception of what is unfit and the laughter which accompanies this are directed, for the most part, to members of other communities. The laughter is choral because it is that in which the whole tribe joins or is prepared to join; but for that very reason it has a monotonous sound. Some differentiation of groups within the community seems necessary, not merely for the constitution of a society, but for the free play of the laughing spirit. Diversity in thought and behaviour is a main condition of the full flow of social gaiety. The germ of such diversity is present in the lowest {259} conceivable type of human community. The institution of male and female in which Nature, as if to combine divine work with human, at once joins together and puts asunder, has been with us from the beginnings of human society; and it might be an amusing pastime to speculate how the males of our ape-like ancestors first gurgled out their ridicule of female inferiority, and how the females managed to use their first rudiment of speech-power in turning the tables on their lords and masters. Some differentiation of rank, too, must have been found in the simplest human societies in the contrast between the old and the young, and the closely connected opposition of the rulers and the ruled. But it would be hazardous to reason that, in the early stages of social evolution, much in the way of exchange of fun passed between those who were presumably kept solemnly apart by the sense of their relative station.