742 PRIMATES 
through the potency of various kinds of selection acting upon the 
slight variations which appeared in individuals in obedience to the 
tendency planted in all living things. These differences manifested 
themselves externally in the colour of the skin, the colour, quality, 
and distribution of the hair, the form of the head and features, and 
the proportions of the limbs, as well as in the general stature. 
Geographical position must have been one of the main elements 
in determining the formation and permanence of races. Groups of 
Men isolated from their fellows for long periods, such as those 
living on small islands, to which their ancestors may have been 
accidentally drifted, would naturally, in course of time, develop a 
new type of features, of skull, of complexion, or hair. A slight set 
in one direction in any of these characters would constantly tend 
to intensify itself, and so new races would be formed. In the same 
way different intellectual or moral qualities would be gradually 
developed or transmitted in different groups of Men. The longer 
a race thus formed remained isolated the more strongly impressed 
and the more permanent would its characteristics become, and less 
liable to be changed or lost when the surrounding circumstances 
were altered or under a moderate amount of intermixture from 
other races—the more “true,” in fact, would it be. On the other 
hand, on large continental tracts, where no mountain ranges or 
other natural barriers form obstacles to free intercourse between 
tribe and tribe, there would always be a tendency towards uni- 
formity, from the amalgamation of races brought into close relation 
by war or by commerce. Smaller or feebler races would be 
destroyed or absorbed by others impelled by superabundant popu- 
lation or other causes to spread beyond their original limits; or 
sometimes the conquering race would itself disappear by absorption 
into the conquered. 
Thus for untold ages the history of Man has presented a shift 
ing kaleidoscopic scene: new races gradually becoming differenti- 
ated out of the old elements, and, after dwelling a while upon the 
earth, becoming either suddenly annihilated or gradually merged 
into new combinations ; a constant destruction and reconstruction ; 
a constant tendency to separation and differentiation, and a tendency 
to combine again into a common uniformity—the two tendencies 
acting against and modifying each other. The history of these 
processes in former times, except in so far as they may be inferred 
from the present state of things, is a difficult study, owing to the 
scarcity of evidence. If we had any approach to a complete 
paleontological record, the history of Man could be reconstructed ; 
but nothing of the kind is forthcoming. Evidence of the anatomi- 
cal characters of Man as he lived on the earth during the time 
when the most striking racial characteristics were being developed, 
during the long ante-historic period in which the Negro, the Mon- 
