Languages

906 million Africans speak over 1000 languages
730 million Europeans speak 35 languages
279 different languages are spoken in Cameroon; in Zaire - 221, Tanzania - 131, Sudan - 132, Tchad - 127

There are three monolingual African nations – Burundi, Rwanda, and Somalia
There are five multilingual African nations with one or more dominant languages – Senegal, Mali, Burkina Faso, Niger, and Zaire
In all the other countries, there is no single dominant language.

Continent, % World Population, % World Languages
Africa, 14%, 33%
Europe, 11.3%, 3%
Asia, 60.5%, 30% [1]

Most of these languages are spoken by culturally and, perhaps to a lesser extent, ethnically diverse people. All these numerous tribes and ethnic groups have had complicated relationships, often involving war, subjugation, and slavery. This is illustrated in Mauritania by the Haratins, or Black Moors, the second largest minority after the Hal-Pulaars. They are the descendants of West Africans enslaved by the North African Berbers. Over time, they came to largely share the Moor culture and language while still being seeing as a distinct group.

The borders of Mauritania, as is the case with much of Africa, were drawn from the logic of outsiders—a river here, a mountain range there, longitude, latitude, and treaties with other foreign governments. This ignored the racial and cultural diversity that exists within that arbitrary landmass. Rivers, for example, are rarely borders in traditional societies. Through trade and transportation they connect people together. Although differences may exist along the entire length of a river, the odds are that two villages on directly opposite banks will share the same language and culture. In Mauritania, the south-western border was drawn along the Senegal River, separating the Hal-Pulaar peoples from their cousins in Senegal and giving the country something of a split-personality between the Moorish north and Black African south.

By favoring certain ethnic groups, colonial governments in Africa could take advantage of these relationships to further their own power. This has left a legacy of governments that tend to represent the interests of whomever the colonists worked with. This, combined with numerous languages, uncomfortable borders, and a long history ethnic clashes makes nationalism an especially difficult concept through much of Africa and leads in part to the seemingly endless civil wars in African nations.

[1] I started making all these numbers up, then found them in a recent issue of Aujourd'hui l'Afrique