238 HEREDITY AND EUGENICS 



civilised countries that birth-rates and death-rates 

 usually rise and fall together. A very good discussion 

 of the subject is by Dean Inge ( 1 9 1 9) . Notwithstand- 

 ing the numerous factors which have been ascribed 

 as causes of the waxing and weaning of birth-rates, 

 populations, and civilisations, we are still largely 

 in the dark as to the fundamental biological signi- 

 ficance of these fluctuations. Did the ancient civilisa- 

 tions fail to maintain themselves on account of 

 climatic changes, soil sterility, malaria, infanticide, 

 losses in war, inbreeding, natural sterility, or racial 

 ennui and hopelessness of outlook ? All of these 

 causes may have been operative in particular cases, 

 but none of them appear to be adequate to account 

 for the submergence of, for example, the classic 

 civilisations of antiquity. We see the sweep of 

 biological wave on wave of population, but the 

 nature of the operative forces which produce these 

 tides is too complex for analysis with our present 

 knowledge. 



A recent wTiter (Nilsson, 1921) discusses the down- 

 fall of Greece and Rome from a racial and biological 

 point of view. He points out that both countries 

 apparently took their origin b}^ the establishment of 

 races by isolation and inbreeding after a mixture or 

 invasion of races had taken place. There was a 

 great diversity of races in the Roman Empire, and 

 Roman rule tended to mix them up. Previously 

 isolation and inbreeding had kept them relatively 

 fixed and developed them as relatively pure races. 

 Under the shelter of Roman peace and Roman 

 administration they mingled, and the result was 

 unlimited hybridising of types, destroying the many 

 fixed types which had existed, and giving rise to 

 instability of disposition and of culture. This blend- 

 ing of man}^ races is regarded as the most destructive 

 agency in the downfall of Rome. This would furnish 



