Phenomena of Inheritance 77 



with regard to several selected traits, viz., genius or marked in- 

 tellectual capacity, artistic faculty, stature, eye color and disease. 

 As a result of his very extensive studies two main principles ap- 

 peared to be established : 



i. The Law of Ancestral Inheritance which he stated as fol- 

 lows: 



The two parents contribute between them on the average one- 

 half of each inherited faculty, each of them contributing one- 

 quarter of it. The four grandparents contribute between them 

 one-quarter, or each of them one-sixteenth; and so oh, the sum 

 of the series 1/2 + 1/4 + 1/8 + 1/16 . . . being equal to I, as 

 it should be. It is a property of this infinite series that each term 

 is equal to the sum of all those that follow: thus 1/2 = 1/4 + 

 !/8 + 1/16 + ...,1/4=1/8+ 1/16 + . . v and so on. The 

 prepotencies of particular ancestors in any given pedigree are 

 eliminated by a law which deals only with average contributions, 

 and the various prepotencies of sex wiith respect to different 

 qualities are also presumably eliminated. 



The average contribution of each ancestor was thus stated 

 definitely, the contribution diminishing with the remoteness of 

 the ancestor. This Law of Ancestral Inheritance is represented 

 graphically in the accompanying diagram (Fig. 24). Pearson has 

 proposed a Law of Reversion according to which the average re- 

 version of offspring to each ascending generation of ancestors is 

 represented by the series .3, .15, .075, .0375, etc. 



Ancestors and Contributors. Theoretically the number of an- 

 cestors doubles in each ascending generation ; there are two par- 

 ents, four grandparents, eight great-grandparents, etc. If this 

 continued to be true indefinitely the number of ancestors in any 

 ascending generation would be (2), in which n represents the 

 number of generations, There have been about 57 generations 

 since the beginning of the Christian Era, and if this rule held true 

 indefinitely each of us would have had at the time of the birth 

 of Christ a number of ancestors represented by (2) 57 or about 

 120 quadrillions, a number far greater than the entire human 

 population of the globe since that time. As a matter of fact, 



