Societies do not evolve quickly or slowly. Please see this post, especially Point 6.

Did they not evolve as quickly? Apart from the difficulties of seeing societies out of a Westernised prism, sub Saharan African societies weren't 'primitive'. Check out /r/african_history to see some sub Saharan African history and civilisations, where beautiful art and pottery was produced, where there were complex and large cities, religions and legal systems, with systems of charitable giving, trade within sub Saharan Africa, metallurgy etc etc, varying between different societies, but there were many incredibly wealthy, urbanised societies such as in Benin, Zimbabwe and along the Swahili Coast, to name a few. In many (most) sub Saharan societies, there have been and continue to be strong oral traditions which parallel Shakespeare, Chaucer and so on with deep complexities, religious symbolism, sub plots and so on, but often overlooked as they were usually not written down until post colonialism or colonialism. Different communities evolved differently, adapting to different needs, environments and so on, but pre colonial Africa had hundreds, thousands, of kingdoms, rural communities, semi nomadic societies and hunter gatherer groups who are and were 'civilised', depending what you mean. Did most have some form of court system? Yes. Did most have a hierarchy, a form of order etc? Yes. Did most have intricate and interesting traditions, folklore and stories? Yes. Did many have knowledge of metallurgy, astronomy and mathematics? Yes. Music traditions from pre colonial sub saharan Africa survive to today, and if you go to museums, you will see breathtaking works of art from a variety of sub Saharan African pre colonial societies. Judging how 'civilised' a society is from a Western point of view is seriously problematic, but even if you discounted oral traditions, different legal systems, the music, arts and so on, sub Saharan African, pre colonial societies would still count as 'civilised' under Western ideals, no?