230 THE REGULATION OF NUMBERS 



taking a man's part ; within a certain time he must clear a piece 

 of land of a given area. 1 Another author gives further details : 

 ' Before he is allowed to choose at all he must prove that he is 

 a man and can do a man's work.' There are various tests. Among 

 others ' he clears a space in the forest to be planted with 

 cassaba, and brings in as much game and fish as pos&ible, to 

 show that he is able to support himself and others '. 2 In Peru 

 a man had to be twenty-four years old before he could marry. 3 

 Von Martius states that the system of marriage by purchase 

 in Brazil is to be regarded as a symbol that the bridegroom 

 can support a family. 4 Men among the Guanas marry when 

 over twenty. 5 



11. The evidence so far adduced shows that the mechanism 

 whereby numbers may be kept near to the desirable level is 

 everywhere present. When inquiring into the nature of the 

 mechanism, we found certain indications that it was effective. 

 The regularity with which certain customs are practised, the small 

 average number of children, and other facts afford strong but not 

 conclusive evidence that an approach is normally made to the 

 optimum number. We may now ask what further evidence there 

 is as to the position in this respect. 



Conclusive evidence is not available. It is only when we are 

 able, as among some of the races in the third group, accurately to 

 measure the average income over a period of years during which 

 numbers are changing that we can arrive at a definite result. With 

 regard to other races we have to adopt methods which, though 

 less precise, nevertheless afford important evidence. We may 

 inquire into the general conditions of life and ask whether there 

 are indications of the approach to the highest standard of living 

 within reach, or whether living is more usually reduced to the bare 

 level of subsistence. We may ask whether famine and starvation 

 frequently occur, what the average physical condition of the 

 people is, whether old age is often reached, whether, in short, the 

 conditions are such as we should expect to find them when the 

 optimum number was approached, or as we should expect to find 

 them when the numbers reached the maximum which could just 

 be kept alive. 



The conception of savage life which formerly prevailed was that 



1 Schomburgk, Reisen, vol. ii, p. 251. 2 im Thurm, loc. cit., p. 221. 



8 Rivero and von Tschudi, Peruvian Antiquities, p. 185. * Von Martius, 



loc. cit., vol. i, p. 109. 6 Azara, loc. cit., vol. ii, p. 93. 





