254 THE DESCENT OF MAN 



becoming domesticated, which implies the power of their 

 breeding freely when first captured, and one chief check to 

 wild men, when brought into contact with civilization, sur- 

 viving to form a civilized race, is the same, namely, sterility 

 from changed conditions of life. 



Finally, although the gradual decrease and ultimate 

 extinction of the races of man is a highly complex problem, 

 depending on many causes which difEer in di£Eerent places 

 and at different times; it is the same problem as that pre- 

 sented by the extinction of one of the higher animals — of 

 the fossil__horsej. for instance, which disappeared from South 

 America, soon afterward to be replaced, within the same 

 districts, by countless troops of the Spanish horse. The 

 New Zealander seems conscious of this parallelism, for, he 

 compares his future fate with that of the native rat now 

 almost exterminated by the European rat. Though the 

 difiiculty is great to our imagination, and really great, if 

 we wish, to ascertain the precise causes and their manner 

 of action, it ought not to be so to our reason, as long as we 

 kee'p steadily in mind that the increase of each species and 

 each race is constantly checked in various ways ; so that if 

 any new check, even a slight one, be superadded, the race 

 will surely decrease in number; and decreasing numbers 

 will sooner or later lead to extinction; the end, in most 

 cases, being promptly determined by the inroads of con- 

 quering tribes. 



On the Formation of the Races of Man. — In some cases 

 the crossing of distinct races has led to the formation of 

 a new race. The singular fact that Europeans and Hindus, 

 who belong to the same Aryan stock, and speak a language 

 fundamentally the same, differ widely in appearance, while 

 Europeans differ but little from Jews, who belong to the 

 Semitic stock, and speak quite another language, has been 

 accounted for by Broca," through certain Aryan branches 



'I' "On Anthropology," translation, "Anthropolog. Review," Jan. 1868, 

 p. 38. 



