Developmental Stage Age Groups and African Population Structure: The Kusasi of the West African Savanna

African population structures based on censuses exhibit a distinctive pattern of distortion. It is often assumed that the cause for this distortion is systematic biases in age estimates by census enumerators and respondents influenced by perceptions of social and biological development. African developmental stage age groups are the cultural codification of such perceptions. I describe developmental stage age groups among the Kusasi of Bawku District in northeast Ghana, and analyze their age and sex structure for a sample of 1,132 individuals from the village of Zorse. I show that differences between men and women reflect differences in biological and social development, and that cultural concepts of developmental stages could influence age estimates to produce the pattern of distortions typical of those found in African population structures based on censuses. This is supported by a comparison of Bawku District population structure based on the Ghana census and an ethnographic sample census in Zorse which eliminated most age estimate biases.