372 EVOLUTION AND GENETICS 



basis for the mental qualities involved as well as for the physical 

 structures. 



Environment and Human Life. Writers have disagreed on 

 the part played by environment in the development of human 

 characters. We must realize that intelligence has given us a 

 degree of control over our environment which removes us almost 

 completely from the direct influence of natural conditions, and 

 such control cannot fail to have an effect. Through the facilities 

 of modern agriculture, transportation, and storage we maintain 

 an almost constant food supply whose seasonal fluctuations are 

 chiefly among the luxuries of diet. Engineering methods give us 

 summer temperatures in our homes during the winter, and warm 

 clothing protects us in proportion to our needs. Our supply of 

 light and water is also carefully regulated. It would be difficult 

 to provide more uniform and favorable surroundings than those 

 of civilized man. 



Environment is only one of the fundamental factors of existence, 

 however, and we cannot expect it alone to shape the life of an 

 organism. If a child grows up in a musical family any musical 

 ability that he may possess is likely to be expressed, but if he 

 lacks ability there is no possibility that he can be made musical. 

 He may be forced through a course of training in music and liecome 

 a mediocre performer, but of such material true musicians are not 

 made. 



With the breadth of opportunity available in modern society 

 it is difficult to avoid the conviction that as man has shaped his 

 own environment, so will the individual shape his. The least 

 that the individual can do is to seek the most favorable environ- 

 ment within his reach, and reach in America is a matter of inherited 

 capacity. The environment of earh' life may facilitate or retard 

 his progress but eventually the life of the individual is bound to 

 be an expression of his heritage. If he has not made himself a 

 good environment, he has shown himself deficient in a fundamental 

 quality of the human race. 



Summary. While human inheritance cannot be studied as 

 readily as that of other organisms, enough is known to show that 

 it is based upon the same principles. There is a material basis 

 similar to that of other animals in the chromosome complex. 

 Anatomical unit characters of several kinds have been traced 

 repeatedly through several generations, and in some cases more 



