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-Monogenists 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 extinction of races-The formation of races-The effects of crossing-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 I am about to enquire what is the value of the differences between them under a classificatory 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 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 species.
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