Dr. Peacock will continue her research in the Ituri region of Zaire. A long term multi-investigator study has focussed on two groups: semi-nomadic Efe pygmies who subsist primarily by hunting and gathering, and village-living Lese horticulturalists. While people such as the Efe are normally expected to have low fertility levels - and this in fact is the case - most often settled horticulturalists are characterized by just the opposite. Prior work however has shown that the Lese fertility is low. The goal of the research is to discover why this is so. Dr. Peacock will continue longitudinal monitoring of variation of gonadal function among both groups. She hypothesizes that high work loads among women contribute to disruption of ovarian function. She will monitor ovarian function through the measure of reproductive hormones in saliva and urine. Work load will be assessed through quantitative observations of individual behavior. Estimation of active infection with sexually transmitted diseases will be determined through gynecological exams. A pilot study of male gonadal function will also be initiated. Population in Africa is expanding rapidly and this defeats efforts to raise the standard of living through development. The population explosion is one of the most serious problems facing third world countries. Dr. Peacock's project may provide insight into natural factors which limit population growth.