CHAP, xx SUMMARY AND CONCLUSIONS 299 



process has been attended with a vast differentiation 

 of life into forms not all of them admirable from an 

 aesthetic or from a guasi-moral point of view. Whether 

 there is advance upon each divergent line, as differen- 

 tiation takes place, may appear doubtful, though the 

 theory seems to affirm it. Differentiation appears to 

 be proclaimed far more clearly than progress, alike 

 by the theory of natural selection and by the phe- 

 nomena of living but irrational nature. 



When we turn to human evolution, we find at once 

 that there are changes. The law of differentiation 

 has still been at work, though its conditions are ob- 

 scure and ill-comprehended. We have negroes, Es- 

 quimaux, Mongols, Caucasians, all probably of the 

 same stock, all very dissimilar. Yet even here there 

 is something quite different from animal evolution. 

 Races of men do not dwell simply side by side, indif- 

 ferent to each other, as plant and animal races do. 

 You may, of course have a society built in separate 

 compartments, as in the institution of caste, or in the 

 simpler and more familiar case of slavery. Yet this 

 differentiation, gross and excessive as it is, belongs to 

 another region of things from animal differentiation. 

 The many castes or the slaves and the oppressors 

 constitute together one society. The potential 

 unity of the race, implied in reason, has already that 

 notable consequence. Accordingly, the marked physi- 

 ological differentiation of the various races of man- 

 kind does not seem to have taken place in a society 

 having relations even of neighbourhood between its 

 several parts. It has been guessed that race differen- 

 tiation was due to natural selection in different regions 



