174 THE EVOLUTION OF MAN 



always offset by a high death-rate, but in civilized society this 



is by no means the case. 



In a recent paper of great interest and importance, Pearl 

 has shown that the "vital index/' that is, th'e ratio of births to 

 deaths within a given time, differs greatly in different elements 

 of our population; it is lowest among the old American stock, 

 and highest among the foreign-born population. In New Eng- 

 land and in New York State, the native population of native- 

 born parents produces only about .8 or .9 of a birth for each 

 death, while in the country at large "the native population 

 produces only a fraction over one baby for each death. In 

 other words, the native population . . . is in about the same 

 state as France before the war, and not in as vigorous a state 

 as the French population is now." As contrasted with this, he 

 says, "Generally speaking, the foreign population produces in 

 this country approximately two babies for every death." 



In so far as this foreign population is equal in quality to the 

 native stock which it is replacing there is no cause for alarm in 

 this, and except for sentimental regrets on the part of the old 

 American stock, it may be welcomed as a rejuvenating factor, 

 but if this foreign stock is in the main inferior in quality to 

 that which it is replacing, then indeed is there cause for con- 

 cern. 



Race Differentiation vs. Race Amalgamation. Another 

 important principle in past evolution which is being reversed in 

 the case of man is that of racial isolation and differentiation. 

 Since all types of mankind interbreed freely, it is evident that 

 distinct races could not have been established and perpetuated 

 except by the aid of isolation, chiefly geographical. On the 

 whole, race differentiation has made for progress; it has led 

 to the establishment of races peculiarly fitted to the environ- 

 ments in which they are found and it has favored the estab- 

 lishment of types superior in certain directions though they 

 may be inferior in others. 



