The type of man who will constitute the future social organism, though a fascinating speculation, cannot possibly be predicted. Of course, we know that the production of more easily digested food, or even predigested, gives the advantage, in the struggle for existence, to those who are not burdened with the expense of producing and maintaining large digestive organs. The future man will, therefore, have fewer teeth, smaller stomach, shorter intestines, and so on, but the evolution of these changes requires tens of thousands of generations. The complete disappearance of the organs and our parasitic dependence upon blood transfusions from domestic animals after the manner of Well's fanciful Martians, would require a period of time longer than that given by the geologists to the earth as a place fit for any kind of life, so that such discussions are as bootless as the topic of man's final disappearance from the earth. The only thing we know is that man must evolve types fit for the tremendously changed conditions of life. Present mental and physical types could not exist even in the Utopia now dreamed of by Socialists. Organisms and their units both change with increasing organization. Man will disappear by evolving into a different creature.
Yet the types in the groups of the immediate future can be predicted, for the process of their production is well under way. The increased variation in brain power, for instance, is a vast change from the conditions of prehistory, when all men were equal because all had to do the same kind of work. It is an invariable rule that when a species develops a part or character, markedly different from the homologous character in the nearest related species, that character immediately proceeds to vary, so that we can confidently predict that future men will be of every conceivable grade of intelligence from the stupid fellow only able to wield a pick-axe under a foreman, to men having genius higher than any we now conceive possible, each limited to a special sphere of intellectual power. Primitive men, by the way, and present savages, have a high degree of intelligence, but it is of a generalized type unfit for the specialties of civilization. We are apt to forget how much ability it requires to make one's living in a rude culture without tools. People who worry about the decay of races should remember that somehow nature has produced higher types than Greece or Rome ever dreamed of, and by the same processes, in the future, exceptional variations will appear with genius beyond our present comprehension.
Physically, man will not differ from present types for a very long time. The chapters on acclimatization and man's evolution show that nature has been an enormous time creating the present types from the first man. Each is fitted to his zone, and in that zone we will find that type, many thousands of years hence, but from the interminable streams of migration we will find intruded specimens everywhere, even though they die out, but this extinction of displaced types will be very slow when we learn how to avoid the causes.
Above all else, future populations will be so dependent that war will be impossible, and the prophet was right in predicting the time when our swords will be beaten into plowshares.
Natural law governs the world and all its inhabitants.