516 



The Journal of Heredity 





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WHY BOYS GROW SHORT OR TALL 



.Symbolical pedigrees of the two students shown at the ends of the line in fig. 12, and again 

 shown in fig. 15. On the left, that of the shortest student (from the four feet, 10 

 inches rank) ; on the right, that of one of the tallest students (from the six ft., one in. rank). 

 Squares represent men and circles women; figures underlined denote measurement in 

 stocking feet. It is obvious from a comparison of the individuals in the ancestry of the 

 two boys that the short student is short principally because his ancestors were short, 

 while the tall one gains his height likewise from heredity. Bad environment might have 

 stunted the latter; good environment could never had made the short student tall. (Fig. 

 14.) 



sponsible for height differences in man. 

 The cause is the same as that producing 

 the tall Learning dent and the short 

 Tom Thumb pop varieties of com. In 

 illustration of this fact the students 

 whose pedigrees have been given kindly 

 consented to be photographed beside 

 the api^ropriate variety of corn on 

 either side of the nine foot pole shown 

 in Figure 15. 



It must not be assumed that environ- 

 ment has no influence at all upon man's 

 stature. The question that the shorter 

 student asked, if he was small because 

 he had smoked since he was eight years 

 old, was not entirely irrelevant desjMte 

 the fact that the taller student had also 

 used tol)acco from his tenth year u])- 

 ward. Evidence shows that environ- 

 ment docs have an effect ujion man's 

 physical as well as mental character- 

 istics. Environment can influence the 

 height of com within certain limits. 

 But the ancestry of the ]3op corn and 

 of the student standing beside it fore- 

 ordain both to a growth of limited pro- 

 jjortiotis even vmder the best environ- 

 ment, while the Leaming.com and the 



boy of tall ancestr\' will both tend to 

 grow tall despite a bad environment. 



The facts that have been presented 

 may appear familiar and the distinc- 

 tions drawn trivial. But the distinc- 

 tions lie at the base of all efforts for 

 human bettemient and are far from 

 trivial in their significance. Although 

 frcquenth' confused by the siinilarity 

 of their immediate effects, environment 

 and heredity as causes are fundamen- 

 talh' different. r^nvironment works 

 ui)on the individual and its effects are 

 transient. Heredity works upon the 

 oft"s])ring and its effects are permanent, 

 from generation to generation. Inherent 

 characteristics only arc transmitted. 

 It has been generally assumed that 

 characters acquired as a response to a 

 good or to a bad environment are handed 

 on to the next generation — that for 

 example a man's college education will 

 affect the mind of his newly-bom chil- 

 dren. Increasing knowledge has failed to 

 support this assumption. "Acquired 

 characters" seemingly cannot be handed 

 on to one's descendants. 



