370 EVOLUTION AND GENETICS 



Erasmus Darwin, has already been mentioned as one of the great 

 contributors to the early history of evolution. Two sons of 

 Erasmus, one the father of Charles, were distinguished men in 

 their chosen fields. Charles himself needs no mention; the fact 

 that his name is almost synonymous with organic evolution in 

 the popular mind is enough evidence of his greatness. Charles 

 Darwin's wife, Emma Wedgwood, was his cousin. Her grand- 

 father was the founder of the famous Wedgwood pottery works. 

 The four sons born to this union were prominent in as many 

 activities. 



Winship's data on the family of Jonathan Edwards, an eminent 

 minister, are a similar evidence of inherited ability. Of 1394 

 descendants identified in 1900 there are listed 295 college gradu- 

 ates, 13 presidents of leading colleges and many in similar offices 

 of less importance, 60 physicians, over 100 clergymen and religious 

 workers, 75 officers in the army and navy, 60 writers, over 100 

 lawyers, 30 judges, 80 public officials including a vice-president 

 of the United States and three senators, and many officials in 

 business enterprises of various kinds. 



The Kallikak Family. The record of this family is even more 

 convincing evidence of the potency of heredity in determining the 

 value of human beings, for it contains contrasting lines of descent 

 from a single ancestor, Martin Kallikak. (This name is also 

 fictitious.) Kalhkak, although of good family, became the father 

 of a feeble-minded son by a feeble-minded woman. The descend- 

 ants of this son have been traced, and out of several hundred 

 none have been above average ability, most have been below 

 average, and more than a quarter were feeble-minded. Later 

 Kallikak married a girl from a good family and the known issue 

 of this union, numlDering almost the same as his other descendants, 

 have been almost without exception respectable citizens of normal 

 ability (Fig. 203). 



The Basis of Mental Traits. Many students of human heredity 

 have attempted to analyze the inheritance of mental qualities 

 without gratifying success. The behaviour of such characters can- 

 not be explained on the basis of simple Mendelian laws, although 

 it is impossible to avoid the conviction that a Mendelian founda- 

 tion is present in some degree of complexity. Even though 

 authorities disagree on the subject it seems that complexity is 

 the keynote to human ability and mental traits. So many different 



