346 



SCIENCE 



[N. S. Vol. XLI. No. 1053 



With, this kind of information behind us, 

 and with the growing conviction that man 

 too is an animal, we naturally turn to the 

 problem of populating the world with the 

 feeling that if human reproduction were 

 subject to only a little of the kind of con- 

 trol that the expert breeder exerts over 

 his stock, the advance of the human species 

 in social efficiency might be incalculably 

 great. 



But here I must invite your attention 

 again and more closely than before to what 

 constitutes an effective human being. Such 

 a member of society is not only a person 

 physically intact and capable of responding 

 to all the requirements of an enormously 

 complex environment, as the best of our 

 domestic breeds do, but he is one who has 

 gathered to himself an untold wealth of 

 experience far exceeding that of any other 

 animal. Moreover, he has not only within 

 himself this vast store of riches, but he long 

 ago devised an immensely complex system 

 of extraneous records in the form of spoken 

 and written languages by which experience 

 could be preserved, handed on to others, 

 and thus made available in a fashion wholly 

 unique. "With language came morals, the 

 arts, science, in short all those features that 

 make up civilization. Thus the older nat- 

 uralists were justified in a measure in re- 

 garding man as a species separate from all 

 the rest of creation, and even we must to- 

 day admit his very unusual character. 

 "When we call to mind this vast array of 

 activities so much more diverse, rich and 

 voluminous than that of any other species, 

 the problem of inheritance in man takes on 

 a very different aspect from that in other 

 organisms. 



Although very little is known about the 

 transmission of the enormously complex 

 inheritance of human beings, there are in 

 this process two fairly well established fea- 

 tures. First, many qualities, some of which 



are of a more physical nature like the color 

 of hair or eyes and others of a more func- 

 tional character like resistance to disease or 

 temperamental conditions, are known to be 

 inherited in man in precisely the same way 

 as the peculiarities of the lower animals 

 are, that is, through the germ. Other pos- 

 sessions, such as language with all its social 

 dependences, are handed on, not through 

 the germ, but by a process of learning, a 

 mode of inheritance which is only most 

 scantily represented among the lower forms. 

 These two types of inheritance, the one 

 characteristic of most organisms, the other 

 more peculiarly human, have gained espe- 

 cial attention in the last few years and have 

 been designated organic and social inher- 

 itance, respectively. That they represent 

 distinct and well-defined processes there 

 can be not the least doubt, but what pro- 

 portion of the total human inheritance is 

 included in each is a matter of much un- 

 certainty. 



From the standpoint of genetics these 

 two types of inheritance are of funda- 

 mental importance. Organic inheritance 

 is the only kind that can be controlled 

 through the reproductive processes, and 

 its product when normal is the rich natural 

 soil in which civilization flourishes. Social 

 inheritance is the work of the educator, 

 using that term in the broadest sense, and 

 its product when normal is civilization it- 

 self. For success it depends first upon a 

 proper organic soil in which to root, and 

 next upon the cultivating influence of a 

 civilized environment. So far as the indi- 

 vidual is concerned social inheritance is 

 essentially a process of learning and our 

 whole educational system is devoted to its 

 operations. Since we receive our social 

 inheritance as an acquired character, to use 

 a biological term, and not through the germ, 

 we can be sure that it will never be con- 

 verted into an organically heritable aggre- 



