To get crap back on track-
Tenacious H: you're right in that any nomadic group is not a Civilization. (Non-Latin speakers: the word Civilization comes form the Latin civila, which means "city". No civilas, no civilization.)
Saying the Scots are already represented by the Celts is one thing, but saying the Zulu represent the Bantu? Yes, the groups are related, but its like saying English are already represented by the Germans. However, I suppose the Bantu are a very broad group, but we definately need more African civilizations. Mali, Songhai, Ethiopia, and Ghana would all be excellent options, perhaps even Benin, Dahomey or Ashanti. Many Westerners are not acquainted with these civilizations, and, as such, think they are inconsequential. This is not so, Westerners are drilled mainly on European history, and Africa is largely neglected.
Songhai, Mali, and Ghana were all Western African trading kingdoms who, at their peak, had arguably the richest empires in the world. They inhabited much of the same territory, in different time periods. Ghana, which had already developed large, organized cities in 300 AD, began to achieve greatness in the 700's and lasted until the 11th century. It became a rich land by controlling the salt and gold trade routes along the continent, supplying the growing Muslim empire with precious metals and goods. Ghana was invaded in 1076, and fragmented soon after.
Ghana gave rise to the kingdom of Mali, which, though it lasted only a few hundred years, achieved great wealth and power. It controlled the legendary trading city of Timbuktu, and its leader Mansa Musa made a pilgrimage to Mecca and tithed enough gold and elaborate art to enrich the Arab empire.
The greatest west African empire, Songhai, followed Mali. It grew so rich off the slave trade and other industries that its tithes to Mecca literally destabilized the world's currency by devalueing the price of gold in the Islamic world and Europe. Its military, though primitive, was strong enough to resist the Europeans and Muslims, and conquer and enslave neighboring kingdoms.
Ethiopia's main bragging point is its age. It was already a rich, well-established country when the Greek culture was starting to rise, and is still a nation today. It was conquered only once, as far as I know, by Italy's fascists.