Final answer:
The wider genetic variation in Africa compared to the rest of the world is best explained by the "Out of Africa" model, with modern humans evolving firstly in Africa before migrating outwards, leading to a broader genetic diversity within the African population.
Step-by-step explanation:
The genetic variation in Africa compared to the rest of the world can best be explained by the "Out of Africa" model. This theory posits that modern humans emerged first in Africa around 200,000 years ago. As these early humans expanded out of Africa, approximately 100,000 years ago, they replaced other human species. However, before leaving Africa, the population had more time and a larger, more diverse environment in which to evolve, leading to a wider range of genetic variations. The genetic variance found in Africa but not elsewhere supports this model, as concluded from the research showing that most human genomes tested outside of Africa have close ties to people in Africa, yet there is a variety of genetic markers in Africans that are not present in other populations worldwide.
Additionally, the fact that modern human features appeared first in Africa and did not flow into contemporaneous populations like Neandertals further strengthens this argument. Crucial to understanding this greater genetic diversity is the longer period of human evolution that occurred within Africa before some groups migrated to other continents. This extended evolution within a geographically varied continent resulted in a broad spectrum of genetic traits.