"But since he [man] attained to the rank of manhood he has diverged into distinct races, or, as they may be more fitly called, sub-species. Some of these, such as the negro and European, are so distinct that, if specimens had been brought to a naturalist without any further information, they would undoubtedly have been considered by him as good and true species. Nevertheless, all the races agree in so many unimportant details of structure and in so many mental peculiarities, that these can be accounted for only by inheritance from a common progenitor; and a progenitor thus characterized would probably deserve to rank as man. It must not be supposed that the divergence of each race from the other races, and of all from a common stock, can be traced back to any one pair of progenitors. On the contrary, at every stage in the process of modification all the individuals which were in any way better fitted for their conditions of life, though in different degrees, would have survived in greater numbers than the less well fitted. The process would have been like that followed by man, when he does not intentionally select particular individuals, but breeds from all the superior individuals and neglects the inferior. He thus slowly but surely modifies his stock, and unconsciously forms a new strain. So with respect to modifications acquired independently of selection, and due to variations arising from the nature of the organism and the action of the surrounding conditions, or from changed habits of life, no single pair will have been modified much more than the other pairs inhabiting the same country, for all will have been continually blended through free intercrossing."[114] The meaning of this is that if you go back to the period when an animal, by the slow process of modification which was continually operating among the preceding organisms, had been raised to the present state of man, and then follow out the divergencies into the distinct races of men, those divergencies would not have occurred in consequence of any one pair having been modified much more than the other pairs inhabiting the same country, but all the individuals would have undergone a continually blending process through unrestrained intercrossing; and those individuals of both sexes, who became in a superior degree fitted for their conditions of life, would have survived in greater numbers than the less well fitted, and would have transmitted to their posterity those peculiarities which tended at last to produce different races of the human family. So that the notion of a single pair of the negro variety, or of a single pair of the Caucasian variety, formed and completed as an independent stock, is not necessary to account for these varieties.