False: beside Egypt, you had the Nubian civilization (influenced by pre-dynastic Egypt but they developed on their own), which was in northern Sudan -- remember that the Sudanese were Christians from the 2nd century until the 11th when the faith was finally extinguished by Arabs -- you can see great works of Christian art in the Galeria Faras in the national museum in warsaw, Poland
also the Ethiopian civilization -- Ethiopians were civilized from at least 1000 BC -- well before much of Europe except Greece. They had their own writing system, cities, roads, etc.
The Garamantian civilization of the Berbers - remember that the Berbers had great civilizations, one of which even threatened Rome - read about Jugurtha and how he kept paying off roman generals.
Then you had the Carthagian colonies - granted, spread by the phoenicians
in fact remember that the Berbers and Egyptians are technically "white men" i.e. Caucasian
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All of these civilizations in the north and the east had concept of Mathematics well before europe
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Sub-Saharan Africa - well before white men, you had arab and Indian traders and conquerors and you had large kingdoms and Empires in west and East Africa. And yes, they had a well developed concept of mathematics before the white man
you are talking about a sub-set in west africa (from nigeria south) and north of RSA.