man had added agriculture to hunting, used hatchets and smooth stone implements, made pottery and baskets, erected houses, controlled fire, had domesticated sheep and cattle, had begun spinning and weaving, lived in stable villages and had a comparatively complex social life. Life was infinitely more worth living in the neolithic period. Compared with the ages that passed before the anatomical and mental characteristics peculiar to man appeared, this increase in well-being—in surplus energy—between the paleolithic and neolithic periods took place with tremendous rapidity. The actual time must be reckoned in tens, perhaps hundreds, of centuries, but, in comparison with the period that had been required for the production of voluntary imitation by biological processes, the interval between the paleolithic and neolithic periods was but a day. Voluntary imitation and invention had increased the rate of progress many-fold.
To review the successive gains through invention, discovery and imitation during the historic period would not strengthen the argument. In these latter days, we know, the power of the western world has far outstripped even the greatest population increase the planet has ever seen and at the same time has raised the plane of living far above the average of even a century ago. We may turn, therefore, to the inferences of sociological importance which may be drawn from the foregoing facts. Not merely do they show, as has been indicated, that the appearance of voluntary imitation marks the beginning of distinctly human history, but they also provide a definite reason why biological deterioration is not greatly to be feared at present and why the sociologist who bases his explanation of society more upon psychology than biology, is right. For, if it is admitted that the time required for the development of man's somatic surplus through the operation of biological processes upon his structural and mental characteristics was indefinitely longer than the period required for creation of all the extrasomatic surplus accumulated since voluntary imitation appeared, then the conclusion is apparently inevitable that, unless for some reason the biological processes that make for degeneration are much more rapid in their action than were the evolutionary processes that produced the ability to imitate voluntarily, human society is able to increase its total surplus even if somatic-surplus remains constant or even declines to some extent. To put it briefly, extra-somatic increase will more than offset a threatened somatic deficit unless the powers of invention and voluntary imitation are impaired. Somewhat differently stated, up to the limit where biological processes seriously affect them, invention and voluntary imitation will increase the sum total of social surplus faster than biological processes will impair that surplus. That this limit is likely to be reached quickly is absurd. To reach it quickly we should have to breed from the most inferior stocks alone. The burden