152 SOCIAL EVOLUTION 



The topography of an inhabited region besides deter- 

 mining the direction and destination of migrations or 

 furnishing protection from the assaults of hostile peo- 

 ples, often results in the more or less complete isolation 

 of a people from the progressive or retarding influences 

 acting upon the general population without the shel- 

 tered valley or far from the lonely island. 



Isolation prohibits much intermixture of different 

 stocks. This tends to accentuate traits already existing 

 in the stock, as potential possibilities. Sometimes de- 

 fects, intensified and inherited, appear with great 

 frequency. Dr. Alexander Graham Bell made a careful 

 genealogical study of western Martha's Vineyard and 

 found that there had been a great deal of intermarrying 

 and a great many consanguineous marriages. The lo- 

 cality is inhabited by farmers and fishermen of average 

 intelligence and good character. Deaf mutes are strik- 

 ingly numerous. In 1880 there was a proportion of 1 

 to 25 of the whole population affected. 38 Further south 

 along the Atlantic coast there are beaches or banks some 

 distance from the mainland. Here there are many con- 

 sanguineous marriages. A wide-spread trait that may 

 be ascribed to this inbreeding is suspicion and mental 

 dullness; and a relatively high frequency of insanity. 39 

 Over sixty-six per cent, of the population of Sardinia are 

 brunettes. Whereas, brunettes on the continental penin- 

 sula of Italy range from thirty-eight per cent, to over 

 sixty-six per cent, of the total population. This shows 

 how the pure color traits of the stock have been preserved 

 by isolation. 40 



ss Davenport, C. B. Heredity in Relation to Eugenics, 1911, pp. 191- 

 192. 



3 Ibid., p. 193. *o Ripley, W. Z.The Races of Europe, p. 253. 



