Possibly racist history question of the day

If its really true that the human populations of the world began in Africa and that therefore Africa is the location of the beginning of human civilization, why is it that there was there a Scramble for Africa? Shouldn't the Africans have already been well established there? Even if the Asian and European populations had better conditions for growth after the Dark Ages, why wasn't Africa already pretty much carved out? Why did they "lose" it again. As the unspeakable question goes, is it a defect in the native African population?