Document Type



Crow’s Index of Opportunity for Selection is calculated for a sample of 287,271 males and 280,985 females bom between 1800 and 1924- The data were obtained from the Utah Genealogical Database. The overall mortality index is 0.19 for males and 0.17 for females, indicating a relatively low level of selection potential due to mortality. The mortality index gener- ally declines through time, and it is higher in urban areas than rural areas until 1890. This may reflect changes in public health conditions. The overall fertility index is 0.39 for males and 0.34 for females, indicating a relatively moderate level of selection potential due to fertility. The fertility component rises during the transition to controlled fertility and then declines. The total selection index is 0.64 for males and 0.57 for females. An analysis of offspring who themselves produce offspring shows that the fertil­ity index is substantially increased by counting only such “successful offspring,” although part of the apparent increase is due to missing data. Inclusion of 1,778 polygynous males in the computation of the fertility index raises it dramatically, even though the proportion of polygynous males is small. The evolutionary implications of these findings are discussed.