what were the causes of the bantu migration

REASONS FOR THE BANTU MIGRATION
The reasons for the migration of the Bantu are not known but they most likely included the following;

Drought and famine: They moved due to the fear of famine, which broke out due to overcrowding and drought. The climate in their cradle land had become unreliable/unpredictable.

Population increase which resulted into over crowding: They migrated due to population pressure, e.g. they became overpopulated in their cradle land. This led to the scarcity of grazing and agriculture land, and so they had to move to look for more land, both for agriculture and for their cattle.

The constant attacks (external pressure) from stronger tribes in West Africa and the Nile valley. They moved due to external pressure, especially due to the migration of the Arabs into West Africa. The Arabs were believed to be more hostile, and so Africans were forced to move southwards.

Internal conflicts from the Bantu tribes: they migrated due to internal misunderstandings/conflicts between the different clans. These conflicts concerned the ownership of agriculture area, the shortage of grazing lands and watering areas.

Epidemics and diseases/natural calamities: The Bantu moved due to natural disasters, e.g. earthquakes, over flooding of rivers like river Niger, sickness, diseases such as Nagana caused by Tsetse flies, sleeping sickness e.t.c.

Search for fertile land: Since they were predominantly farmers, the Bantu migrated
in order to find more land which could be more fertile than the cradle land, which could no longer support them. E.g. they had changed from hunting and gathering fruits, to farming and had even discovered new crops such as yams, banana, and e.t.c

Love for adventure: They moved due to their desire for adventure, i.e. they wanted to find out what was happening in other areas.

Group influence: Some moved because they had seen their relatives and friends move.

Need for water and pasture for their animals forced them to move.

The Bantu migrated in order to export their iron-working culture. They had discovered the knowledge of iron working and had invented iron tools. These iron tools had transformed the agricultural sector by making the clearing of land fro cultivation faster and more efficient.