The Boll Weevil was an insect that destroyed crops in Alabama in Georgia. The reason they were effect at different times is because they had different crops and the Boll Weevil migrated at different times.
The peoples of West Africa had rich and diverse histories and cultures centuries before Europeans arrived.
Before Imperialism, Africa was a very diverse land with hundreds of languages and cultures. Societies ranged from centralized government states, to village communities, to nomadic hunter-gatherer societies.
A European author stated : "Africa had no history prior to European exploration and colonization, that there is only the history of Europeans in Africa."