Many people today attribute the cause of the numerous conflicts especially in central Africa to be the division of the land to non-national states. And indeed, today the armed conflicts mostly consist of intra-state wars of manifold cultures/races. What is the consensus on this topic in the current research? Would there be more or less damaging conflicts in case the states had been divided into national states in course of decolonization?
There are three theories of ethnic conflict, each of which provides a different expectation for Africa. These theories are summarized here (Williams, 2015). That article has many citations, so I won't repeat them all here.
Each of the three theories below provides different expectations. The high level summary is:
- Primordialism suggests that the conflict is inevitable. One group killing or subjugating the other is the only real solution. Strong institutions can help mitigate the harm of violence, but never solve it.
- Instrumentalism suggests that ethnic violence is rational. The only way to solve the problem is to resolve the underlying problems that violence is trying to solve. Sharing a state sometimes does this, if the state is able to distribute resources in a prudent way.
- Constructivism suggests that ethnic violence is based on fluid social identities. These identities change based on macro-level political conditions. Putting rival groups together in the same state is expected to improve their relationship and decrease violence.
Notably, some of these theories make opposite predictions.
Primordialism supposes that ethnicity (and other characteristics) are factors which are ascribed to individuals. Individuals receive their social status from historical social traits (such as being born into a certain family) and cannot change them once they are born. In this theory, ethnic violence stems from conflict between primordial groups. Conflict within states is an outgrowth of ancient, primordial conflicts that the state cannot possibly resolve.
This theory would predict that if multiple combative ethnic groups are forced into the same state, there will be civil conflict (perhaps even war) within that state. However, if the groups are placed in their own states then you may have ordinary war because the two groups would be driven to fight each other.
You can read about this theory more in Samual Huntington's famous book, The Clash of Civilizations. Huntington takes a very broad view (he supposes that there are only a handful of primordial groups, while other authors suggest that there could be thousands, such as different tribes or ethnicity).
Additionally, strong institutions can mitigate violence, but never resolve it. For example, strong law enforcement and judicial systems can help mitigate violence, but can never solve the problem.
Instrumental theory supposes that political violence is pseudo-rational. Political actors have rational reasons for choosing to organize along ethnic lines. That is counter-intuitive to some people (how could racism ever be rational?), but here are a few examples:
- Ethnic groups often share values and concerns. If I wanted to mobilize political action, I may find it expedient to focus on ethnic groups whose concerns and values make them likely to agree to my proposal.
- Ethnic groups often share a geographic area. If two ethnic groups are fighting over natural resources, than they are enemies because of their rational self-interest.
In this theory, ethnic violence is rational. Ethnicity is not the cause of the violence, it is merely a proxy. This theory would predict that violence will continue as long as their are important disparities which correlate with ethnic divides. Unfortunately for your question, this answer is not very simple. States could encourage assimilation, if they provide material benefits for abandoning ethnic identities (making ethnicity-based conflict no longer rational). However, states could also re-enforce ethnic conflict by providing benefits inequitably to certain ethnic categories.
Constructive theory supposes that ethnic identity is a fluid social construct. In this sense, we learn our ethnicity from the people around us - and our ethnicity can change over the course of our lifetimes. Ethnic conflict is a kind of narrative or story that plays out between ethnicity. Under this theory, you could view people as "actors" who rehearse and play out "scripts" based on their "part" (their ethnicity).
This theory tends to focus on high-level causes of violence. Generally, this theory would predict that if members of conflicting ethnic groups were forced to interact closely (such as by putting them in the same state) they would change their narratives and ethnic violence would decrease. This is the controversial contact hypothesis. It's possible to avoid that cooperation if each ethnic group forms their own political parties and "sticks to their own kind" - preventing any kind of meaningful collaboration.
Contrariwise, allowing each ethnic group to have their own state would reinforce social conflict narratives and allow ethnic conflict to escalate to war between states.