Colonization, particularly colonization resulting from the actions of imperialist nations, undoubtedly has significant effects on the indigenous populations. In the nineteenth century, Africa was a largely new frontier, and the mad dash for territories tended to accelerate the social effects brought about by colonization.
The imperialistic European nations who arrived in Africa imposed their social structure, forms of government, and mores on the indigenous populations. As a result, perhaps the most devastating change brought about by European imperialism in Africa was the displacement of African cultures in favor European ones. European nations would install governments that superseded the existing tribal confederacies, displacing them as the ultimately authority for the native population. So effective was this practice that when European nations began to pull out of Africa after World War I, this often resulted in power vacuums filled by local dictators.
In addition, in much the same way that early colonists of the New World brought with them diseases against which the Native Americans had no defense, the African population had no defense against European diseases, greatly altering African societies.
This being said, not all of the changes wrought by European imperialism in Africa during the nineteenth century were negative. The measures undertaken by European nations helped to establish a solid infrastructure that was nonexistent before their arrival. In addition, the imperialist nations taught the indigenous populations more productive means by which to farm their land.