PROGRESS AND DIFFERENTIATION. 281 
for life acts so as to transform human society, just as 
it modifies animals and plants, and in both cases con- 
stantly produces new forms. The comparison of the phe- 
nomena of human and animal transformation is especially 
interesting in connection with the laws of divergence and 
progress, the two fundamental laws which, at the end of the 
last chapter, we proved to be direct and necessary conse- 
quences of natural selection in the struggle for life. 
A comparative survey of the history of nations, or what 
is called “universal history,” will readily yield to us, as the 
first and most general result, evidence of a continually im- 
creasing variety of human activities, both in the hfe of in- 
dividuals and in that of families and states. This differenti- 
ation or separation, this constantly increasing divergence of 
human character and the form of human life, is caused by 
the ever advancing and more complete division of labour 
among individuals. While the most ancient and lowest 
stages of human civilization show us throughout the same 
rude and simple conditions, we see in every succeeding 
period of history, among different nations, a greater variety 
of customs, practices, and institutions. The increasing divi- 
sion of labour necessitates an increasing variety of forms 
corresponding to it. This is expressed even in the for- 
mation of the human face. Among the lowest tribes of 
nations, most of the individuals resemble one another so 
much that European travellers often cannot distinguish 
them at all. With increasing civilization the physiognomy 
of individuals becomes differentiated, and finally, among the 
most highly civilized nations, the English and Germans, 
the divergence in the characters of the face is so great that 
we very rarely mistake one face for another. 
