In anthropological terms...
Periphery: Least developed countries. They produce raw materials, such as lumber and ore.
Semi-periphery: Semi-developed countries. They produce mostly raw materials, but some technology.
Core: Most developed countries. They manufacture technology and "ideas".
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Most of Africa (if not, all) falls under the periphery. Without the periphery, there could be no core.
Why is Africa the periphery? Some would blame early imperialism (from already more developed countries, such as Italy, Holland, France, etc) for raping Africa's resources and, culturally speaking, imposing their values upon it. Thus, the peoples of Africa could never develop themselves as others have.
I don't know what your educational background is, but taking any kind of Anthropology class (such as the 101 class that I learned this from) is pretty interesting. Of course, it's all theories, but at least you become informed of all the different theories so that you can theorize, yourself
