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THE PRINCIPLES OF HEREDITY 



human inheritance is not a good place to start such a study. Most of 

 our knowledge of heredity has come from experimental breeding of 

 plants and animals with differing characteristics. Human beings can- 

 not thus be bred experimentally and, even if they could, they have such 

 a long generation cycle and so few offspring they would not be good 



Photos by Winchester 



Fig. 32.1. Some physical characteristics which are inherited in man. From left to 

 right and top to bottom these are: Dimpled cheeks (dominant). Attached ear lobe 

 (recessive). Widow's peak, a point of the hair line which extends down in the center 

 of the forehead (dominant). Ability to fold the tongue (dominant). Clubbed thumb 

 (dominant). Ability to roll the tongue (dominant). Mongolian eye-fold, upper eye- 

 lid folded downward (dominant). Albino (recessive). Elongated pupil of the eye 



(dominant). 



