You are wrong we have alphabet it called Ge’eze. Ge'ez script - Wikipedia Ge’eze Script is used in Ethiopia and Eritrea. read more
"Many regions of sub-Saharan Africa have long histories of contact with the Mediterranean world, the Middle East or the Islamic world, and India, and this is reflected in the writing systems and prestige languages used in this region". read more
Sub-Saharan Africa was host to a long list of prosperous, advanced imperial states and kingdoms, many of which could easily be argued to be more "advanced" (depending on your definition of advanced) than their European contemporaries. read more