THE DESCENT OR ORIGIN OF MAN 251 



large as New Zealand, and the Sandwich Archipelago with 

 its diversified stations. On the contrary, it is known that 

 the present inhabitants of Norfolk Island are nearly all 

 cousins or near relations, as are the Todas in India, and the 

 inhabitants of some of the Western Islands of Scotland} 

 and yet they seem not to have suffered in fertility." 



A much more probable view is suggested by the analogy 

 of the lower animals. The reproductive system can be 

 shown to be susceptible to an extraordinary degree (though 

 why we know not) to changed conditions of life; and this 

 susceptibility leads both to beneficial and to evil results. 

 A large collection of facts on this subject is given in chapter 

 xviii. of volume ii. of my "Variation of Animals and Plants 

 under Domestication." I can here give only the briefest 

 abstract; and every one interested in the subject may consult 

 the above work. Very slight changes increase the health, 

 vigor, and fertility of most or all organic beings, while 

 other changes are known to render a large number of ani- 

 mals sterile. One of the most familiar cases is that of tamed 

 elephants not breeding in India, though they often breed in 

 Ava, where the females are allowed to roam about the forests 

 to some extent, and are thus placed under more natural 

 conditions. The case of various American monkeys, both 

 sexes of which have been kept for many years together in 

 their own countries, and yet have very rarely or never bred, 

 is a more apposite instance, because of their relationship to 

 man. It is remarkable how slight a change in the condi- 

 tions often induces sterility in a wild animal when captured ; 

 and this is the more strange as all our domesticated animals 

 have become more fertile than they were in a state of 

 nature; and some of them can resist the most unnatural 

 conditions with undiminished fertility.*' Certain groups of 



^ On the close relationship of the Norfolk Islanders, see Sir "W. Denlson, 

 "Varieties of Vice-Eegal Life," vol. i., 1870, p. 410. For the Todas, see 

 Colonel Marshall's work, 1813, p. 110. For the Western Islands of Scotland, 

 Dr. Mitchell, "Edinburgh Medical Journal," March to June, 1865. 



^ For the evidence on this head, see "Variation of Animals," etc., vol. IL 

 p. 111. 



