Sub-Saharan Africa is incredibly huge, and the pre-colonial period was centuries, and centuries long. The colonial period began in earnest in the late 19th century, I would argue. And before this, there were immense regional differences across the continent. Africa was not a homogenous, 'merry' or 'peaceful' continent (a view that some African historians prior to the 1970s unfortunately adhered to) before European contact. Many pre-colonial sub-Saharan African societies were both violent and peaceful, involved in exchange and trade, engaged in both subsistence and "wage" style economies, patriarchal, matriarchal, and everything in between. Indian Ocean exchange networks, for example, from about the fall of Rome onwards, involved people from across Asia and East Africa - and all manner of cultural and religious tension occurred, in the way it does today. So your question needs to be narrowed substantially.

In response to your question the level of violence we've seen for the past century or so is almost certainly a reaction to the top down method of colonialism practised by the European powers, in particular Belgium and France, but sub-Saharan Africa is huge and varied and pre-colonial history is a truly massive timescale. I will, however, say that there were several powerful, wealthy and advanced civilisations that existed prior to European settlement (in particular the Kingdoms of Axum, Mali and Songhai among others *)and their contact with other settlements, tribes and civilisations were, as is to be expected, bloody*. There were also a number of civilisations and tribes that made money by enslaving prisoners of war and selling them to other tribes and the European tribes once they arrived in Africa * However, directly responding to your question I think the quantity of violence probably did not change overly much and pre-colonial Africa was almost certainly similar to pre-Expansion Europe in that lots of wars were fought between different civilisations and empires but I feel the nature of the violence probably changes in the post-colonial period. The introduction of the concept of nation to the African continent produced a different type of inter-tribal violence that is closer to a civil war that has sparked the atrocities in DRC, CAR and Rwanda to name a few. It is also certainly the case that the death toll in these conflicts is higher to that in the pre-colonial period because of the industrialisation of warfare and better weapons etc.