372 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
512, the theoretical number. Nevertheless this calculation will serve 
to show how widespread our ancestral lines are, and how nearly related 
are all people of the same race. 
Davenport concludes that no people of English descent are more 
distantly related than 30th cousins, while most people are much more 
closely related than that. If we allow three generations to a century, 
and calculate that the degree of cousinship is determined by the num- 
ber of generations less two, since first cousins appear only in the third 
generation, the first being that of the parents and the second that of 
the sons and daughters, we find that 30th cousins at the present time 
rot °) Parents 
fou 2 3 9 Grand Pts 
SI SI SIP [sl] eo] gl] Q lered ree 
slelalelaleisigisleialeis|ela/gl@t at aa pts 
TTT eee 
TTT TTT TTT TT TTT TT 
Fic. 65.—Diagram of Galton’s ‘‘Law of Ancestral Inheritance.” The whole 
heritage is represented by the entire rectangle; that derived from each progenitor 
by the smaller squares; the number of the latter doubles in each ascending 
generation while its area is halved. (From Conklin, after Thomson.) 
would have had a common ancestor about one thousand years ago or 
approximately at the time of William the Conqueror. As a matter of 
fact most persons of the same race are much more closely related than 
this, and certainly we need not go back to Adam nor even to Shem, 
Ham, or Japheth to find our common ancestor. 
2. The Law of Filial Regression is the second principle which 
Galton deduced from his statistical studies, or it may be called the 
tendency to mediocrity. He found that, on the average, extreme 
peculiarities of parents were less extreme in children. Thus “the 
stature of adult offspring must on the whole be more mediocre than 
the stature of their parents, that is to say more near to the mean or 
mid of the general population”’; .and again, “the more bountifully a 
