INHERITANCE OF LEFT-HANDEDNESS 1 



PROFESSOR FRANCIS RAMALEY 

 University of Colorado 



Introduction.— The fact that left-handedness "runs in 

 families" has probably attracted the attention of many 

 observers, yet the method of inheritance has not been 

 fully studied. Many people imagine the condition to 

 depend entirely upon training or imitation. There is 

 thus much of guesswork concerning the true nature of 

 the condition. 



Literature— A considerable bibliography of left- 

 handedness has recently been cited by Professor H. E. 

 Jordan. 2 Most of his references are, however, to articles 

 of little value, especially since nearly all of them were 

 written previous to the modern period of genetic study. 

 Professor Jordan puts forth the tentative opinion that 

 left-handedness is a recessive character. Unfortu- 

 nately the data which he presents consist chiefly of a few 

 selected pedigrees from which the reader can obtain very 

 little information. He suggests more than once that some 

 of his cases are examples of the spontaneous appearance 

 of left-handedness in a family. If such spontaneous 

 development were so frequent the whole population 

 would, in a few generations, be left-handed. The appear- 

 ance of a left-handed child in a family without left- 

 handed ancestors for three or four generations is not to 

 be considered remarkable, for this is the way in which 

 recessive characters frequently behave. 



Method of Obtaining Data.— At the beginning of a 

 course of lectures on heredity in the University of Col- 



Vol. II, pp. 19-29 and 113-124, 1911. 

 730 



