facts of human history, with a skill which brings out some novel results of prime scientific importance. One of those results, regarding the social development of man, is so significant as to justify some fullness of explanation.
The idea which determines the course of inquiry in the chapters referred to was first suggested by Mr. Wallace; and it is that, when the intelligence of an animal has arrived at a certain stage of flexibility, natural selection will begin to prefer mental to physical variations. That is to say, when an animal has become so intelligent that he can meet some of the exigencies of life by varying his intelligent contrivances instead of by incurring some slight physical change, there will then be a tendency for the more flexible intelligences to survive in the struggle for life: and obviously so much more can be done, and so much better done, by securing variations in mental rather than in physical structure, that after a while the amount of mental change will become enormously great and rapid as compared with the amount of physical change. Hence a man may be very much like an ape in physical structure, while his thoughts may be as-much higher than the ape 's thoughts "as the heavens are higher than the earth."
This is not only a very brilliant but a very useful suggestion. Mr. Wallace, however, has never followed it up, but has left it over for Mr. Fiske, who has applied it with such striking effect to the specific problem of the genesis of man, that he may almost be said to have made it his own. Before the problem of man's vast intellectual and moral superiority, Mr. Wallace retreats discomfited, even after having hit upon the idea which, when thoroughly considered, goes quite half-way toward explaining it; and, like other discomfited inquirers, past and present, he appeals to the supernatural for aid and comfort, when he was bound to go on and overcome the difficulties of the inquiry. Just here the question is taken up in the work before us. Having shown, in accordance with Darwin and Spencer, the general evidences for the evolution of the higher forms of life and intelligence from the lower forms, Mr. Fiske recognizes that the special question of the evolution of man's great mental preeminence requires a special mode of treatment. Some factor has come in which has greatly modified the phenomena with which we have to deal when considering the development of the animal kingdom in general. And this factor, Mr. Fiske maintains, is the existence of social combination, by which man is most conspicuously different from any other animal. The general question of the evolution of society is, therefore, treated preliminary to the question of the origin of man. Having ascended, zoologically and psychologically, from the primitive marine vertebrate to the point of departure of man from the apes, the line is changed, and a descent is made, psychologically and historically, from the higher to the lower phases of human society, with the view of reaching, as nearly as may be, the same point of departure. This inquiry into social evolution gives a formula for human progress, and lands us in the same general theory of primitive society which has been so well illustrated by Maine, Lubbock, and McLennan. The state, in its grandest complications, having been shown to be a development from the primeval clan or family group, very much as a complex organism ia developed from the aggregation of amœba-like units, the question comes up, How did permanent family groups arise? Here we come to the very marrow of the problem, for, having passed from a race of primates in which each individual lives for himself, to a race of primates in which the conduct of the individual is determined with reference to the needs of a permanent group of which he is a member, we have then passed from manlike ape to apelike man. Both the intellectual and the ethical supremacy of man have been brought about by social conditions, of which this formation of permanent family groups was the earliest in order. How, then, was this great step taken?
Mr. Fiske gives an entirely new answer to this question, though when once suggested it is so obvious that it seems as if it ought to have occurred spontaneously to every one who has thought upon this subject. A preliminary to the answer is given in the chapter on the "Evolution of Mind," where it is briefly pointed out that the increase of intelligence in an animal, beyond a certain
