184 THE PRINCIPLES OF HEREDITY 



of violence, or famine, or old age, or disease. But deaths 

 from all these causes, except the last, are now comparatively 

 rare amongst them much rarer than formerly during the 

 time of their perpetual wars. The vast majority die of 

 imported diseases exactly the same diseases as white men 

 die of. But their mortality is invariably much higher than 

 that of white men ; they perish on an average at a younger 

 age. All this is not mere hypothesis. It can be proved by 

 reference to carefully collected and tabulated statistics 

 published by every Department of Public Health in America, 

 Australasia and Polynesia. The cause of the sterility cannot 

 be demonstrated with the same precision ; but it is hardly 

 necessary to invent fanciful causes, when a reasonable one is 

 to hand. The high mortality indicates a high sick-rate, and 

 presumably illness is as much a cause of sterility in the New 

 World as in the Old, and among savages as among civilized 

 people. 



306. The Spanish Conquest of the West Indies was 

 followed by the swift disappearance of the natives. To that 

 end the Spanish unconsciously adopted the most effective 

 means possible. They satisfied their greed by forcing the 

 natives to labour in plantations and in mines, and their 

 religious enthusiasm by compelling attendance in churches 

 and cathedrals. In other words, they placed the natives 

 under conditions the most favourable for acquiring the 

 diseases which they imported by every vessel. When the 

 native population dwindled it was replaced by Negro slaves 

 from West Africa. The case of the latter is extremely inter- 

 esting. No colony of Africans has ever succeeded in Europe 

 or Asia, where the mortality from tuberculosis grows so great 

 that the immigrants soon become extinct. 1 Nevertheless 

 even in West African forests Negroes have undergone some 

 evolution against tuberculosis. 2 It was not enough to enable 

 them to persist in the densely-peopled parts of Europe and 

 Asia, but it was enough to enable them to persist under the 

 conditions they found in the islands and on the mainland of 

 America. In America tuberculosis, as compared to its 

 prevalence in Southern Europe and Asia, had as yet spread 

 but little. The slaves were taken to the warmer parts of the 

 country and employed mainly in agriculture. They had a 

 special start and were placed under conditions that grew worse 



1 A stream of African slaves was poured into parts of Europe and 

 Asia for many years. They have left no trace on the population. 



2 Many accounts have been published of the prevalence of tuber- 

 culosis in Africa. See Hirsch, vol. iii., pp. 189-92. 



