K. Pearson and A. Lrk 



373 



certainly a " pn^f'crcntial maliiig"* ta,kinL,' jilaco. I tliink we inay saf'ely assort 

 that thü Hrst factor of sexual selectioii is aclivo in uvau. I now turn to the sucond 

 factor, " assortatrivi' mating." If certain woiuen are rejecled, at any rate as 

 mothers «f adiilt cliililren, do tho rcinaindor mate at random as far as the above 

 three cliaracters are couceriied ? Tlie aiiswcr is inost decidedly in the negative, 

 there is a very sensible reseniblance in size betvveen husbaud and wit'e, which 

 « priori I should have said was iiardly cenceivable. Table II. gives the direct 

 and cross coefficients f'or assurtative niating in man. 



TABLE II. 



Assurtative Mating. Based on 1000 tu 10-30 Cases of Hushand and Wi/e. 



We See at once that between the same ph\'sical characters in the hiisband 

 aud wife of adult children there is a correlation of upwards of '2, a most re- 

 markable degree of reseniblance, greater thau that of great-grandparents to 

 their great-grandchildren (about •lOf), and probably greater than that of first 

 Cousins to eaeh other. We could hardly want stronger evidence of the existence 

 of assortative mating in man, i.e. of the actuality of sexual selection. I had 

 previously fouud| from iVlr Galton's FaiHilt/ Records, that the correlation in 

 stature between hushand and wife was •09 + "05, but between father and mother 

 of adult offspring was '18 + ^02. Cousidering the coniparative smallness of material, 

 the latter result is in very good agreement with the present, but it seems to 

 iudicate that a portion of the observed reseniblance in the parents of adult 

 offspring is due to reproductive selection, i.e. honiogamy being a factor of fertility. 

 If the parents of adult children are on the average more alike than first cousins, 

 then it foUows that any evils which niay flow from first cousin marriage depend 

 not on likeness of characters, but on sanieness of stück§. 



That the whole result, further, is not due to a mere general custom of men 

 and wonien mating with persons not differing widely from tliem in stature, is 



* Phil. Trans. Vol. 187, p. 253 et seq. See especially p. 258. 



t Biometrika, Vol. ii. p. 221. J R. S. Froc. Vol. (ifi, p. 30. 



§ 1 have dlscussed this point more at lengtli, li. .S. Proc. Vol. 06, p. 29. 



Biometrika ii 48 



