Figure 2. Female baboon (P. hamadryas) linear regression of serum cortisol by age. (A) 24 baboons from the colony at Southwest National Primate Research Center (cortisol = -24.7*X+735.1 ng/ml; P=0.0007); (B) 31 baboons from the Oklahoma University Primate Center (colony cortisol = -23.7*X+1521; P=0.039). The data for the Oklahoma baboons are reproduced from their publication (Willis et al. 2014). Red symbols represent five baboons that were included in the immunohistochemistry studies reported here.