We combine the date-of-observation found in Murdock’s Ethnographic Atlas and a newly-constructed dataset on the date-of-colonization at the ethnic-group level to study the effects of the duration of colonial rule on a variety of political, economic, and social characteristics of ethnic groups in Africa. We find that the duration of colonial rule caused a dramatic shift in gender roles in Africa by increasing the relative status of men in lineage and inheritance systems but also reducing polygyny as a marriage system. A causal role for the duration of colonial rule is confirmed by a difference-in-difference analysis that uses never-colonized ethnic groups as a control group and by an analysis of changes in kinship terminology that tests for within-group changes in descent and inheritance rules. We are able to rule out missionary influence and Islam as mechanisms for these effects.