
Extract the answer to the question from the following context.
Question: Why are they three ethnic groups the cause of many of the problems present in Nigeria?
Context: Ethnocentrism, tribalism, religious persecution, and prebendalism have affected Nigerian politics both prior and subsequent to independence in 1960. Kin-selective altruism has made its way into Nigerian politics, resulting in tribalist efforts to concentrate Federal power to a particular region of their interests. Nationalism has also led to active secessionist movements such as MASSOB, Nationalist movements such as Oodua Peoples Congress, Movement for the Emancipation of the Niger Delta and a civil war. Nigeria's three largest ethnic groups (Hausa, Igbo and Yoruba) have maintained historical preeminence in Nigerian politics; competition amongst these three groups has fuelled corruption and graft.

historical preeminence
