460 SOORTVORMING EN EUGENETICA 
When a certain amount of variability exists, species can arise, but 
only when isolation of some kind follows. 
In every essential way the causes of variation and the processes of 
heredity in man follow the same laws as in the lower organisms. 
The human races of the Anthropologists are not necessarily identical 
with species, they may be species, they may consist of several species, 
or of parts of several species. 
Eugenics has up till now concerned itself almost entirely with the 
study of varietal characters in man. The study of the existance of natu- 
ral groups in humanity is more inportant than the study of the inhe- 
ritance of details, if we are interested in the possibilities of improving 
the inherited makeup of humanity, even if these varietal characters 
are of extreme importance to the individual and to the group in which 
the individual occurs. 
The causes of inheritable aberrations, and their origin by preventa- 
ble occurances should be, more than hitherto, a subject for study, ra- 
ther than the inheritance of these same aberrations after they occur. 
In this matter, as in other, related branches of medical research, pre- 
vention is more important than cure. 


