436 THE ORIGIN OP TRADITION 



polygamy . . . Economic causes are again associated with the de- 

 velopment of organized warfare and the substitution of the enslave- 

 ment of prisoners for their slaughter, liberation, or adoption.' ^ 



In other words social institutions are correlated to a considerable 

 extent with economic systems, and in tracing economic systems 

 to differences in the ' wealth ' of the environment and to differ- 

 ences in contact, we are at the same time accounting to the extent 

 of this correlation for the existence of most social institutions. 

 Those aspects of tradition which are not correlated with the 

 economic system are obviously often explicable as due to 

 the direct influence of the environment ; for differences in the 

 environment which have little or no bearing on the economic 

 system may give rise to differences in these aspects of tradition. 

 It has often been pointed out, for example, that the trend of 

 legends is explicable as due to certain aspects of the environment ; 

 thus in Assyria legends were largely connected with floods. In 

 large part, therefore, differences in fertility and differences in 

 degree and kind of contact account not merely for progress in 

 skill but also in large measure for many social institutions, and 

 those aspects of social institutions which are not so to be explained 

 are in part due to the influence of aspects of the environment 

 which do not contribute directly to fertihty, and in part to a 

 complicated interaction of tradition. It was remarked that, so 

 far as can be seen, the more conscious methods of adjusting 

 the level of population to the optimum number are not correlated 

 with the economic system. There is no evidence of infanticide 

 and abortion, for example, being so correlated. The occurrence 

 of these institutions among certain races irrespective of the 

 economic conditions may be accounted for by differences in the 

 environment which do not affect wealth. We have seen that 

 certain methods must of necessity be employed, and the adoption 

 of one method in one place and of another in some other place 

 may be due, for example, to the presence in one area of plants by 

 the use of which abortion can be brought about, or the presence 

 in another area of an instrument designed for some other purpose 

 which can be employed for this object. In other areas the practice 

 of killing deformed children from superstitious motives may have 

 been developed into a regular custom of infanticide, or the taboo 

 upon intercourse for short periods may have become developed 

 into a practice of abstaining for prolonged periods. 



' Hobhouse, Wheeler, and Ginsberg, loc. cit., p. 254. 



