252 THE DESCENT OF MAN 



animals are mucli more liable than others to be affected 

 by captivity; and generally all the species of the same 

 group are affected in the same manner. But sometimes a 

 . single species in a group is rendered sterile, while the others 

 are not so; on the other hand, a single species may retain its 

 fertility while most of the others fail to breed. The males 

 and females of some species when confined, or when allowed 

 to live almost, but not quite free, in their native country, 

 never unite; others thus circumstanced frequently unite but 

 never produce offspring; others again produce some off- 

 spring, but fewer than in a state of nature; and, as bearing 

 on the above cases of man, it is important to remark that 

 the young are apt to be weak and sickly, or malformed, 

 and to perish at an early age. 



Seeing how general is this law of the susceptibility of 

 the reproductive system to changed conditions of life, and 

 that it holds good with our nearest allies, the Quadrumana, 

 I can hardly doubt that it applies to man in his primeval 

 state. Hence if savages of any race are induced suddenly 

 to change their habits of life, they become more or less 

 sterile, and their young offspring suffer in health in the 

 same manner and from the same cause ^as do the 'elephant 

 and hunting-leopard in India, many monkeys in America, 

 and a host of animals of all kinds, on removal from their 

 natural conditions. 



We can see why it is that aborigines, who have long 

 inhabited islands, and who must have been long exposed 

 to nearly uniform conditions, sjjould be specially affected 

 by a ay change in their habits, as seems to be the case. 

 Civilized races can certainly resist changes of all kinds far 

 better than savages; and in this respect they resemble do- 

 mesticated animals, for though the latter sometimes suffer 

 in health (for instance, European dogs in India), yet they 

 are rarely rendered sterile, though a few such instances 

 have been recorded." The immunity of civilized races arid 

 domesticated animals is probably due to their having beeo 



" "Variation of Animals," etc., vol. ii. p. 16. 



