The behavioral development of 96 baboons was systematically recorded from birth to 84 months of age. Eight behaviors were selected as criteria for examining the effects of early rearing experiences (mother-peer vs peer-peer), gender, age, and cohort as possible sources of variance in the development of affinitive behaviors of this species. Stepwise multiple regression was used to analyze the data and provide quantitative descriptions of the relationships between the selected independent variables and the rates of social behavior during maturation. Among the behaviors studied, three types of developmental patterns were identified. Embrace and groom shared the first developmental pattern; muzzle-body and muzzle-muzzle, the second; and contact, hold, huddle, touch, the third. Gender differences were evident in only the first behavior pattern group. Age was a strong predictor of behavioral performance rate in all but huddle. Cohort, or the combined effects of age, body size, and temporal peer grouping, was an important predictive factor in all but contact and muzzle-muzzle behavior. Early rearing experiences did not produce any significant differences in performance of the affinitive behaviors studied. It is suggested that genetic control of maturation shapes the development of these behaviors in baboons, regardless of subtle environmental experiences.