1 66 The Descent of 3 Tan. Fast I, 



CHAPTER VII. 



On the Eaoes of Man. 



riie nature and yalie of specific characters — Application to the races o 

 iLan — Arguments in favour of, and opiiosed to, ranking the so-called 

 races of man as distinct species — Sub-species — Monogenists and poly- 

 genists — Convergence of character — Numerous points of resemblance in 

 body and mind between the most distinct races of man — The state oi 

 man when he iii-bt spread over the earth — Each race not descended from 

 a single pair — The extinction of races — The formation ot races — The 

 effects of crossing — Slight influence of the direct action of the con- 

 ditions of life — Slight or no influence of natural selection — Sexual 

 selection. 



It is not my iDtention here to describe the several so-called races 

 of men ; bnt 1 am about to enquire what is the value of the dif- 

 ferences between them under a classiiicatory point of view, and 

 how they have originated. In determining whether two or more 

 allied forms ought to be ranked as species or varieties, naturalists 

 are practically guided by the following considerations; namely, the 

 amount of difference between them, and whether such differences 

 relate to few or many j)oints of structure, and whether they are 

 of physiological importance ; but more especially whether they 

 are constant. Constancy of character is what is chiefly valued 

 and sought for by naturalists. Whenever it can be shewn, or 

 rendered probable, that the forms in question have remained 

 distinct for a long period, this becomes an argument of much 

 weight in favour of treating them as species. Even a slight 

 degree of sterility between any two forms when first crossed, or 

 in their offspring, is generally considered as a decisive test of 

 their specific distifictness ; and their continued persistence 

 without blending within the same area, is usually accepted as 

 sufficient evidence, either of some degree of mutual steiility, or 

 in the case of animals of some mutual repugnance to pairing. 



Independently of fusion from intercrossing, the complete 

 absence, in a well-investigated region, of varieties linking 

 together any two closely-allied forms, is probably the most 

 important of all the criterions of their specific distinctness ; and 

 this is a somewhat diiferent consideration from mere constancy 

 of character, for two forms may be highly variable and yet not 

 yield intermediate varieties. Geographical distribution is ofte i 

 brought into play unconsciously and sometimes consciously ; so 

 that forms living in two widely separated areas, in which most 



