Sex ratio of livebirths in Micronesia.

A growing body of data extends Hunt's earlier findings from Yap to suggest a characteristic Micronesian pattern of highly masculinized secondary sex ratios. Using materials from an extensive family record register for pre-World War II Guam, it is now possible to examine parental age and birth order effects in a Micronesian population in which the overall sex ratio of livebirths to 3,406 formally wed and fertile couples was 109.6. In contrast to the results of most studies among Euroamerican groups, secondary sex ratios on Guam were significantly higher for higher order births and for paternal age at last recorded birth to older couples. This apparent anomaly is resolved, however, and James' hypothesis of human sex ratio determination is supported when universalistic assumptions of declinin coital frequencies with spousal age and marital duration are replaced by more appropriate and population-specific ethnodemographic information. © 1995 Wiley-Liss, Inc.