Africa is the most genetically diverse continent on Earth, harbouring more human genetic variation than all other regions combined. On average, an African genome contains nearly a million more genetic variants than a non-African genome.
This unparalleled genetic richness exists for several fundamental reasons:
The Cradle of Humanity: Modern humans (Homo sapiens) evolved in Africa approximately 200,000 to 300{,}000 years ago. Because humans have lived here longer than anywhere else, they have had more time to accumulate and distribute genetic mutations across the population.
The "Out-of-Africa" Bottleneck: Roughly 50,000 to 60,000 years ago, a small subgroup of early humans (estimated at roughly 10,000 people) migrated out of Africa to populate the rest of the globe. Because this migrating group represented only a fraction of the total African population, they took only a fraction of the continent's genetic diversity with them.
Deep Ancestral Lineages: Extensive studies—such as those published in Science—have identified over a dozen distinct ancestral populations within Africa alone. Groups like the San (Khoisan) in Southern Africa and rainforest hunter-gatherers represent some of the oldest, most divergent continuous lineages in the human family tree.
Environmental & Cultural Adaptation: Africans live in drastically varied environments, ranging from deserts and tropical rainforests to high mountain ranges. This exposure to diverse climates, diets, and infectious diseases has driven strong local genetic adaptations over millennia.
Source: https://www.sciencedirect.com/science/article/pii/S0002929722003172
https://www.science.org/doi/10.1126/science.1172257
