276 HUMAN BIOLOGY 



to the most ultramodern advocate of promiscuity, certain 

 assumptions are stated or implied. One of these is that, if 

 biological factors alone ruled, all sex unions would be 

 transitory, or promiscuous; the converse being that, when 

 human sex Hfe is observed to be otherwise, the conventions 

 of the group bar the way. In other words, every individual 

 would be promiscuous, if he were permitted. The alternative 

 assumption, and one stoutly defended, is that biologically 

 man is monogamous; that the association of one man 

 and one woman tends to be of long duration, that occasional 

 promiscuity and plural unions are social developments. It is 

 observable that, in either case, the appeal is made to biolog- 

 ical factors as determiners. It may be profitable, therefore, to 

 consider some of the possible ways in which biological factors 

 may control marriage, rather than the reverse. Our usual 

 way of approaching problems of control is to consider biology 

 the offender and society the discipHnarian. The danger 

 here is in taking too much for granted. 



Thus, polygyny has been explained as due to an excess 

 of women, or to a variation in the sex ratio. 



THE SEX RATIO 



At the outset we assumed that in a normal community 

 the sexes would be approximately equal, but careful investi- 

 gations of the sex ratio in man indicates a shght tendency 

 for males to predominate at birth. Here, however, we are 

 concerned with the sex ratio at marriageable age, or the 

 survival sex ratio. Even the birth-rate ratio for males and 

 females is a survival ratio, for many die in embryo, con- 

 cerning which rehable statistics are wanting. Again, the 

 infant mortahty tables for some national populations show 

 sex differences in the survival rate, and vital statistics, 

 in general, a difference in the death rate, the summation of 

 which gives a higher survival ratio for women. This is 

 evident in the census tables for Great Britain, United States, 

 France, Germany, Sweden, and some other countries. 

 In all of these countries monogamous marriages are enforced, 

 from which it would appear that an excess of marriageable 

 women is accumulating. This is undoubtedly true, but to 

 see the relation of this excess to marriage calls for a careful 



