1Department of Anthropology, The George Washington University, 2Department of Anatomy and Neurobiology, Washington University School of Medicine, Department of Anthropology, Washington University, 3Department of Anthropology and Center for the Study of Human Origins, New York University
Thursday Afternoon, 301D
Kinda baboons (Papio kindae) are the smallest and least sexually dimorphic of extant Papio, and studies of their cranial morphometrics have suggested a distinctive developmental trajectory. To investigate possible proximate causes, we compared body mass with blood serum levels of testosterone, estradiol, insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3) and insulin C-peptide in 32 female and 44 male Kinda baboons from Kafue National Park, Zambia. Their ages, estimated from dentition, ranged from 1 to 215 months.
IGF-I and testosterone predicted body mass in male Kinda (R2 = 0.54, p <0.01), and IGF-I predicted mass in females (R2 = 0.27, p <0.01). IGF-I and testosterone concentrations were higher in males than females (IGF-I: U(1)=301, p<0.01; T: U(1)=202.50, p<0.01), and estradiol was higher in females (U(1)=212.00, p=0.02). In males only, C-peptide concentrations were positively correlated with IGF-I (r = 0.52, p = 0.01). When compared with other species (P. anubis and P. hamadryas), Kinda IGF-I concentrations were closest to those of anubis, with hamadryas IGF-I significantly higher than either (F(2,373)=8.97, MSE=0.19, p<0.01). Intriguingly, in both male and female Kinda, IGFBP-3 was undetectable by our assay. Since IGFBP-3 prolongs the half-life of circulating IGF-I and also facilitates delivery of IGF-I to cellular receptors, this suggests that the bioavailability IGF-I in Kinda may be considerably affected during development. Overall, these results suggest that IGF-I and testosterone influence the developmental trajectory of Kinda baboons, and that their smaller adult body size might be related to unusually low concentrations of IGFBP-3.
Supported by NSF-BCS 1029302, 1029323, and 1029380.