Ethnic boundaries are less sharply drawn in Gabon than elsewhere in Africa. Most ethnicities are spread throughout Gabon, leading to constant contact and interaction among the groups, and there is no ethnic tension. One important reason for this is that intermarriage is extremely common and every Gabonese person is connected by blood to many different tribes. Indeed, intermarriage is often required because among many tribes, marriage within the same tribe is prohibited because it is regarded as incest. This is because those tribes consist of the descendants of a specific ancestor, and therefore all members of the tribe are regarded as close kin to each other. French, the language of its former colonial ruler, is a unifying force. The Democratic Party of Gabon (PDG)'s historical dominance also has served to unite various ethnicities and local interests into a larger whole.