ASSORTATIVE MATING IN MEN 477 



This tendency to mate within the tribe is a factor of first-rate bio- 

 logical and sociological importance, serving as it does to maintain 

 racial boundaries. But if sexual selection be a real factor in the evolu- 

 tion of races — in the differentiation of groups as well as in their main- 

 tenance — its action must be sought within the race, an intra-racial sex- 

 ual selection must be demonstrated. 



Sexual selection in man may, as Pearson long ago pointed out,^ 

 be of two kinds, preferential mating and assortative mating. By 

 preferential mating one understands that certain classes of women are 

 discriminated against by the average man, or by men as a class, or 

 vice versa. By assortative mating one means that in the population of 

 men and women who do marry, there is a definite tendency for certain 

 classes of men to marry particular classes of women, and conversely.* 

 An almost prophetic quotation from Pearson may render the distinc- 

 tion clear. 



For example, preferential mating might lead in a highly social community 

 to the rejection of consumptive mates, while assortative mating might through 

 localization or community of habit, lead to considerable consumptive correlation. 

 Thus sexual selection as a whole may influence in diverse ways the inheritance 

 of the consumptive taint. 



Another illustration faces us in the problem of deaf mutism. Nor- 

 mal individuals discriminate against deaf mutes, for obvious reasons. 

 There is a stringent segregation of the class, resulting from educa- 

 tional and social conditions, and as a result there is for the people, as 

 a whole, a strong assortative mating, hearing people as a class marry- 

 ing hearing, and deaf marrying deaf. 



The scope of this review is limited to a discussion of the quantita- 

 tive results which have been attained for assortative mating.^ 



It is needless to say that a subject so fascinating to man as any- 



the lower animals, it certainly plays a large part in influencing sexual choice 

 among primitive men and more subtly among us in civilization. Just as soon as 

 a social group recognizes the possession of certain physical traits peculiar to 

 itself — that is, as soon as it evolves what Giddings has aptly termed a 'con- 

 sciousness of kind' — its constant endeavor thenceforth is to afford the fullest 

 expression to that ideal." 



Westermarck ("History of Human Marriage," pp. 362-373, 1901) gives a 

 terse summary of the social prejudices, tribal practises and laws concerning 

 marriage between different castes, tribes or elans. Others are to be found in 

 various sociological works. 



2 Pearson, K., Phil. Trans. Boy. Soc. Lond., A, Vol. 187, pp. 257-258, 1897; 

 also "Grammar of Science," 2d ed., pp. 421-437, 1900. 



* Thus in man sexual selection is a somewhat more complicated process than 

 it has been assumed to be in the mass of writings on the lower animals. 



° The quantitative data bearing directly on the problem of preferential 

 mating are few. See K. Pearson, Phil. Trails. Boy. Soc. Lond., A, Vol. 187, p. 

 258, 1897; "Grammar of Science," 2d ed., pp. 425-428, 1900; Biometrika, Vol. 

 2, pp. 270-272, 1903. 



