The answer to this question can be found in Chapter 19 of Guns, Germs, and Steel. In this chapter, entitled "How Africa Became Black," Diamond describes the processes that contributed to Africa's remarkable diversity. Even within the complex patterns of human movement that characterize Africa's history, Diamond sees Madagascar as an "anomaly." Madagascar, it seems, is linguistically different than the rest of the continent. Unlike people on the African mainland the people of Madagascar speak an Austronesian language, sprinkled with Bantu (one of the major language families on the mainland) words from Kenya. This is because, Diamond tells us, the ancestors of the modern people of the island seem to have originated on the island of Borneo, in Indonesia. From there, Diamond suggests that they may have arrived there via trade between East Africa and India. Thus the people of Madagascar have a different background and language from any people in Africa.