NON-MATHEMATICAL SCIENCES 185 



become strengthened through repeated use. In 

 general it may be said to be always adapting 

 itself to the circumstances under which it lives. 

 At one time it was generally supposed that 

 such adaptation of the individual could in large 

 measure be communicated to its offspring, thus 

 providing a means for the adaptation of a 

 whole species to changing conditions, more 

 rapid than natural selection, and independent 

 thereof. 



This is the theory that has been repudiated 

 by modern biology. Indeed, the evidence which 

 has so far been accumulated shows that there 

 cannot be much inheritance of physical traits 

 which have been acquired in the lifetime of an 

 individual. It is true there are certain curious 

 facts still to be explained. In examining the fos- 

 sil remains of man, it is seen that in the earliest 

 stone age, when food w^as consumed in its natu- 

 ral state, the human tooth was very large and 

 powerful, and at each successive period the 

 tooth has kept well adapted to the current 

 habits of eating. The changes appear to have 

 been more rapid than could be readily ac- 

 counted for by the survival of the fittest, since 

 unnecessarily strong teeth could hardly be a 

 serious handicap ; but there are many unknown 



