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THE DESCENT OF MAN. 
Part I. 
CHAPTER VII. 
On the Baces of Man. 
The nature and value of specific characters — -Application to the races 
of man — Arguments in favour of, and opposed to, ranking the 
so-called races of man as distinct species — Sub-species — Mono- 
genists and polygenists — Convergence of character— Numerous 
points of resemblance in body and mind between the most distinct 
races of man — The state of man when he first spread over the 
earth — Each race not descended from a single pair — The ex- 
tinction of races — The formation of races — The effects of cross- 
ing — Slight influence of the direct action of the conditions of life 
— Slight or no influence of natural selection — Sexual selection. 
It is not my intention here to describe the several 
so-called races of men; but to inquire what is the 
value of the differences between them under a classi- 
ficatory point of view, and how they have originated. 
In determining whether two or more allied forms 
ought to be ranked as species or varieties, natu- 
ralists are practically guided by the following con- 
siderations ; namely, the amount of difference between 
them, and whether such differences relate to few or 
many points 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 specifes. Even a slight degree of 
sterility between any two forms when first crossed, or 
in their offspring, is generally considered as a decisive 
