The spread of Islam to Africa not only led to the formation of new communities in Africa, but it also reconfigured existing African communities and empires to be based on Islamic models. The spread of Islam across much of the northern third of Africa resulted in profound effects on both those who converted and those who didn't. Islamization also linked Muslim Africa even more closely to the outside world through trade, religion, and politics. Trade and long-distance commerce were carried out in many parts of the continent and linked regions beyond the Muslim world. Until about 1450, however, Islam provided the major external contact between sub-Saharan Africa and the world.