THE EXTINCTION OF RACES. 185 



animals have become more fertile than they were in a state of 

 nature; and some of them can resist the most unnatural condi- 

 tions with undiminished fertility." Certain groups of animals 

 are much 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, whilst the others are not so; on the other 

 hand, a single species may retain its fertility whilst 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 pro- 

 duce some offspring, 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 off- 

 spring 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 re- 

 moval 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, should be specially affected by any 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 domesticated animals, for though the lat- 

 ter 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 

 and domesticated animals is probably due to their having been 

 subjected to a greater extent, and therefore having grown some- 

 what more accustomed, to diversified or varying conditions, than 

 the majority of wild animals; and to their having formerly 

 immigrated or been carried from country to country, and to dif- 

 ferent families or sub-races having inter-crossed. It appears 

 that a cross with civilized races at once gives to an aboriginal 

 race an immunity from the evil consequences of changed condi- 



*i For the evidence on this head, see 'Variation of Animals,' &c., 

 vol. ii. p. 111. 

 « 'Variation of Animals,' &o., vol. ii., p. 16. 



