MAN 229 



Those with no biological training have now no difficulty 

 in accepting as fact the idea that man came into being by 

 the same process of evolution as the rest of the organic 

 world. But even in these cases it has been a long struggle 

 against prejudice, and the scientific study of heredity is 

 too recent to have outgrown it. We will, therefore, not 

 confine our argument strictly to the logic of the question. 

 Inheritance in man has actually been studied by the same 

 general methods as have brought such wonderful results 

 Lq other organisms, and corroboration of every detail has 

 been the outcome. 



When one says the fundamentals of Mendelism have 

 • been supported in detail by investigations on the human 

 race, he does not mean to imply that the critical investiga- 

 tions needed to establish the Mendelian hypothesis in the 

 beginning were supplied by such data. This is obviously 

 impossible because of inability to control matings. The 

 only records which can be analyzed are pedigrees of 

 families carrying some striking hereditary phenomenon. 

 Such a method is unsatisfactory because the data must be 

 gathered second-hand through several generations — 

 often by untrained workers. It is necessary to work 

 backward instead of forward, to be content with frag- 

 mentary information, to realize the high percentage of ex- 

 perimental error. What is meant by corroboration of 

 Mendelism in human heredity is simply that starting with 

 the assumption of the truth of the law, all human data 

 have been found to fit. But it is often very difficult to say 

 whether the inheritance of a particular human trait is 

 dominant or recessive, whether it is controlled by one or 

 by several factors, whether it is sex-linked or independent. 



Several skeletal abnormalities unquestionably show a 



