the arrival of voluntary imitation marks the beginning of continuity in human history. Thereafter custom and tradition were possible.
The effect on surplus of the arrival of voluntary imitation is, however, the subject to which the preceding discussion has been merely a preliminary. For the effect on surplus was sufficient to free man to a considerable extent from the domination of purely biological processes and to make progress thereafter, as Professor Ward is continually reminding us, essentially a psychological process. The capital fact is this: whenever, after voluntary imitation appeared, a new discovery or invention was made, that discovery or invention rapidly became the property of the entire group. To whatever extent the relative amount of energy expended for survival was lessened for one individual it was lessened for all. Whatever addition was made to the surplus energy of the discoverer was likewise made to the surplus of all members of the group. Thus the inventors of bow and arrow, of canoe and hoe, immeasurably increased the surplus of society at large. So, from this time forth society increased its wealth, added to the bodily surplus of its members those economic goods which could be easily converted into bodily surplus, developed extra-somatic surplus as well as somatic surplus.
At this point a Malthusian might object that during all the early history of man population tended to increase rapidly enough to keep the surplus of every individual low. Even if this were so, it is nevertheless true that every gain increased the total energy available. A greater population in itself meant a greater total surplus, for, at times, the struggle for existence was suddenly alleviated and at such times the more individuals there were the greater was the sum of human energy freed from the effort to merely maintain existence. Such periods of rapid progress must have occurred many times in history. Every migration into a more favorable habitat, every invention and discovery, has tended to permit the size of human groups to increase and usually has tended to increase longevity as well. The use of fire, the invention of tools, the beginning of agriculture, the domestication of animals, the discovery of means of navigation, all these things increased the surplus at divers times and in divers places. How tremendous was the increase in social surplus gained by the combination of invention and voluntary imitation in the early periods of man's progress is indicated by a comparison of the differences between paleolithic and neolithic culture. From the earlier period rough stone implements of the chase, arrow points and what may have been spear points, but no hatchets, are found. Plentiful indication of cave-life, but, in general, no evidence of cultivation, of pottery or use of fire has been unearthed. Domesticated animals were probably non-existent. Social life was doubtless extremely simple.
Contrast the neolithic culture. When that stage first was reached