Programs of Research


PROGRAMS OF RESEARCH

Reproductive Ecology
Our long involvement in work on reproductive ecology continues, with a sustained emphasis on breastfeeding, birthspacing, and child health and survival. In collaboration with Catherine Panter-Brick, a study of acute endocrine/neuroendocrine effects of breastfeeding in two sympatric groups, Tamang and Kami, was the subject of Joy Stallings' dissertation and provided direct evidence for divergent pathways by which endocrine effects of suckling and interbirth interval are mediated. Such work supports our earlier contention that there is no key factor driving breastfeeding contributions to birth spacing; rather, a network of mediating and moderating factors assume varying strength and valence in a context-, developmental- and behavior-sensitive manner.
Several years ago, we became interested in using naturalistic "challenge tests" for more dynamic measures of functional capacity and endocrine regulation. The study of time course of prolactin response to suckling, mentioned above, was our first application of this approach. Wsith Virginia Vitzthum, we completed sample collection for a study of acute endocrine responses to exercise by ovarian cycle phase among Bolivian women at high altitude. The study comprises two groups, one rural, one urban, and is the first to investigate exercise effects on ovarian activity in women with chronically high physical workloads and variable nutritional status. Currently under analysis is a parallel study of the effects of workload, status and lifestyle incongruity on diurnal testicular and adrenocortical activity in men in the rural population. The surprising intial results indicate that the diurnal rhythm in salivary testosterone is nearly absent: evening testosterone is as likely to be higher as lower than morning values. This study substantially expands and corroborates an earlier series, also on Bolivian men, of diurnal salivary testosterone done by us with Cynthia Beall.
Relevant Publications
1998 T. McDade and C.M. Worthman, "The weanling's dilemma reconsidered: a biocultural analysis of breastfeeding ecology." Journal of Developmental Behavioral Pediatrics 19:286-299.
1998 J.F. Stallings, C.M. Worthman, and C. Panter-Brick, "Biological and behavioral factors influence caste differences in prolactin levels among breastfeeding Nepali women." American Journal of Human Biology 10:191-210.
1996 J.F. Stallings, C.M. Worthman, R. Coates, and C. Panter Brick, "Prolactin response to suckling and maintenance of postpartum amenorrhea among intensively breastfeeeding Nepali women." Endocrine Research 22 (1):1-28.
1995 R. Stavisky, E. Russell, J. Stallings, E.O. Smith, C.M. Worthman, and P.L. Whitten, "Fecal steroid analysis of ovarian cycles in free-ranging baboons." American Journal of Primatology 36:285-97.
1993 C.M. Worthman, C.L. Jenkins, J.F. Stallings, and D. Lai, "Attenutation of nursing-related ovarian suppression and high fertility in well-nourished, intensively breastfeeding Amele women of Lowland Papua New Guinea." Journal of Biosocial Science 25:425-43.
1992 C. Beall, C.M. Worthman, K.P. Strohl, B. Gothe, M. Barragan, and J. Stallings, "Salivary testosterone concentration of Aymara men native to 3600m." Annals of Human Biology 19: 67-78.
1990 C.M. Worthman, J.F. Stallings, and C.L. Jenkins, "Breastfeeding patterns and reproductive function among lowland Amele women of Papua New Guinea." American Journal of Physical Anthropology 81:320.
1987 C.M. Worthman and J.W.M. Whiting, "Social change in sexual behavior and mate selection in a Kikuyu community." Ethos 15:145-165.
1980 M.J. Konner and C. Worthman, "Nursing frequency, gonadal function, and birth spacing among !Kung hunter-gatherers," Science 207: 788-791.



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