Programs of Research
PROGRAMS OF RESEARCH
||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.
||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.
||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.|
||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.
||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.
||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.
||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.
||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.
||C.M. Worthman and J.W.M. Whiting, "Social change in sexual behavior and mate selection in a Kikuyu community." Ethos 15:145-165.
||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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