HEREDITY 287 



influences that improve the inborn qualities of a race," is known 

 as eugenics. The argument of the eugenicist is simply this: If 

 man has succeeded through artificial selection or controlled 

 breeding in improving domestic animals and plants, it should 

 also be possible by similar means to improve the inborn qualities 

 of the human race, since man is no exception to the laws govern- 

 ing the heredity of other animals. A few of the characters of 

 obvious importance to the human race are discussed in the 

 following paragraphs. 



Mental Ability. — There is good evidence that mental ability, or 

 the lack of it, is inherited; but it is difficult to measure it in 

 absolute units, such as can be applied to characters like stature 

 or weight. Education and training do not create mental 

 ability so much as provide opportunity for its development and 

 expression. Environment plays an important part in providing 

 suitable opportunity for the fullest realization of mental ability. 

 Therefore, the actual accomplishments of two persons of equal 

 mental ability may differ because of differences in opportunity 

 for mental development. On the other hand, environment 

 alone, however favorable, cannot make up for low-grade ability, 

 for the simple reason that heredity in such cases establishes 

 fixed limits to accomplishment. Thus, in the case of Charles 

 Darwin, the author of the theory of evolution by natural selec- 

 tion, we have an example of marked mental ability, exhibited 

 consistently through a number of generations as a result of 

 heredity. Darwin's own accomplishment was of a very high 

 order and marks him as one of the greatest biologists. His 

 paternal grandfather, Erasmus Darwin, was a physician, natu- 

 ralist, and poet. He was interested in the problem of evolution, 

 to which he made interesting contributions and to other subjects 

 as well. His maternal grandfather, Josiah Wedgwood, was the 

 originator of Wedgwood pottery. His own father was a suc- 

 cessful physician and his sons have achieved eminence in science. 

 It is true, of course, that Darwin was favored in the enjoyment 

 of desirable environment, which enabled him to pursue his work 

 in relative comfort, though he was an invalid throughout the 

 greater part of his life. It is therefore possible that his books 

 on evolution might never have been written had he been poor and 

 his time crowded with the duties of earning a livelihood. On 

 the other hand, he might have spent his life in invalid ease, had 



