Have you ever wondered why most African bright minds who go to study in the west end up working there?
This is my simple analysis. When they land to Europe or America, African scientists work hard, sometimes harder than the "home-boys/girls". They are determined to reach the apex of science.
After completion of the training, they have "too much" knowledge that there are no labs available in Africa to accommodate them. So, instead of putting their knowledge to waste, they decide to stay in the west where they can be more useful with labs and equipment available.
Now it is a challenge for the African governments to set up high-tech labs so that they retain their "brains".