The scientists’ first step was to collect DNA from a diverse set of
Africans. Africa is the most culturally and linguistically diverse
place on Earth, so it was important to take a wide sample of
individuals from all corners of the continent. In total, they collected
2,432 DNA samples from 113 diverse and distinct groups of people from
across the African continent as well as 60 non-African groups. They
sampled everyone from the Mozabite Berbers of Morocco to the
hunter-gatherer San of the Kalahari Desert, and many in between.
But the hard work didn’t stop there. The scientists then examined
1,327 genetic markers across the human genome for each individual
studied. While many studies focus on a particular part of the genome
such the mitochondrial DNA or the Y chromosome, this study took a
comprehensive approach. Finally, the researchers used sophisticated
statistical techniques, piecing together how these populations from
Africa and around the world were the same, and how they were different.
The results confirmed that Africa has the highest genetic diversity
of any continent, as many scientists have proposed. In fact, the
authors found genetic diversity to decrease the further one traveled
away from Africa. Genetic diversity is often used as a measure of how
long ago humans inhabited a region — conventional wisdom places the
earliest humans in East Africa, which had exceptionally high genetic
diversity according to this study, though an analysis by the
researchers put the origin of the human expansion farther south near
the border of Namibia and Angola.