In Jared Diamond’s Pulitzer Prize-winning Guns, Germs and Steel he states that, “History followed different courses for different peoples because of differences among peoples’ environments, not because of biological differences among peoples themselves.” This view revolutionized the understanding of human variation in terms of politics, culture and the subjugation of some groups by others. However, it is the biological variation in human populations that can now help researchers understand the conditions that made this history occur in the first place.

Africa has long been argued to be the original home of the human species. Previous studies have estimated that the most recent common ancestor of all modern humans lived approximately 200,000 years ago. Now, the most comprehensive genetic survey to date has estimated the geographical region in Africa where these ancestors are most likely to have originated.

Research by Sarah A. Tishkoff of the University of Pennsylvania and an international team of collaborators, published in the current issue of Science, analysed 121 African populations, 4 African American populations, and 60 non-African populations for variations at 1327 nuclear microsatellite and insertion/deletion markers. Their results identified 14 ancestral populations in Africa and determined that the most likely region for the emergence of modern humans was along the coast of southwest Africa near the Kalahari Desert (around the South Africa-Namibian border).

According to the review in Science Daily:

The new data goes far toward equalizing the genetic picture of the world, given that most genetic information has come from European and Asian populations. But because it comes from Africa, the continent on which the human lineage evolved, it also sheds light on the origins of human life.

By locating the region with the highest level of genetic diversity, Tishkoff and colleagues have created a map reflecting a kind of “impact crater” of human variation. The African continent already has the most diverse human genomes of any region on the planet, with reduced diversity across the Eurasian continent and the least diversity among indigenous Americans. By tracking the genetic variations within African groups they further suggest that a single population emigrated from Africa about 250 generations ago whose descendants travelled the globe displacing other groups of early humans.

As The New York Times reported:

Dr. Tishkoff’s team has also calculated the exit point from which a small human group — maybe a single tribal band of 150 people — left Africa some 50,000 years ago and populated the rest of the world. The region is near the midpoint of the African coast of the Red Sea.

This population may have been migrating with the herds of wild game, or escaping a severe drought for a milder climate, but they would inadvertently initiate a colonization process that changed the world, and their species, in profound ways. This migration to a region of abundant cereal grasses and domesticable animals resulted in a legacy of human ascendancy over the natural world that, now, may ultimately result in the collapse of human civilization. It’s fascinating to imagine what members of this group were thinking as they looked onto the distant landscape and pondered what their future would hold in this new world.

Reference:

Tishkoff, S., Reed, F., Friedlaender, F., Ehret, C., Ranciaro, A., Froment, A., Hirbo, J., Awomoyi, A., Bodo, J., Doumbo, O., Ibrahim, M., Juma, A., Kotze, M., Lema, G., Moore, J., Mortensen, H., Nyambo, T., Omar, S., Powell, K., Pretorius, G., Smith, M., Thera, M., Wambebe, C., Weber, J., & Williams, S. (2009). The Genetic Structure and History of Africans and African Americans Science DOI: 10.1126/science.1172257