MENDELIAN PEOPOETIONS AND THE IN- 

 CREASE OF EECESSIVES 



PROFESSOR FRANCIS RAMALEY 

 University of Colorado 



Eecently in working over some data 1 on the inherit- 

 ance of lefthandedness, certain questions came up, 

 which seem of considerable interest, as: Does the pro- 

 portion of lefthanded people remain the same from cen- 

 tury to century or does it diminish or increase? In any 

 case, how does the result come about! Although well 

 aware of the present-day aversion to arm-chair biology, 

 it yet seems that these problems can hardly be attacked 

 from the experimental side, and that a theoretical dis- 

 cussion may be of some value. 



It may be stated at the outset that I consider left- 

 handedness to be a true Mendelian recessive, 2 and also 

 that there is no selective mating with reference to the 

 character. There seems also no reason to suspect that 

 lefthanded people exhibit less fertility 3 than normal in- 

 dividuals. If these suppositions are correct, the con- 

 dition offers a happy opportunity for study, since most 

 human characters thus far examined are such as might 

 be likely to be affected by selection. 



Concerning the first question asked above, no positive 

 answer can be given, for there are no statistics. It is 

 probable that the affection is a very old one, and not of 

 recent origin. If it tends to increase it might be expected 

 that a very considerable part of the population would 

 now show the condition, while if it is decreasing, we 



1 As yet unpublished. 



Breeders' Magazine, Vol. II, pp. 19-29 and 113-124. My own observations 

 confirm this belief, 

 k * My own records even suggest the opposite condition, but this is prob- 



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