SEX RATIO IN ESCAZU, COSTA-RICA, 1851-1901

The long-term behavior of the secondary sex ratio (SSR) is of interest to human biologists partly because it could be responsive to cyclical environmental stress or to long-term changes in the environment. Inde ed, the SSR has been reported to fluctuate in a seasonal pattern or to have a long-term trend in some populations but not in others. Here, I study the behavior of the SSR in Escazu, Costa Rica, from 1851 to 190 1. Of particular interest is whether the SSR was seasonal, because Mad rigal (1994) reported that in this population mortality is seasonal. T he data were successfully modeled according to the Box-Jenkins methodo logy without incorporating a seasonal parameter. Thus the SSR did not fluctuate seasonally. For the time period under study no long-term tre nd was observed in the value of the SSR, which tended to fluctuate in accordance with the expected values. Finally, the behavior of the SSR was not observed to be influenced by the various epidemics that affect ed Escazu. These results indicate that, although severe epidemics and seasonal mortality affected the population, the community's SSR was no t significantly affected by these stresses.