The study looked at genetic material from across the African continent
A group of scientists have unveiled what they say is the most comprehensive study ever of African genes.
Published following a decade of study, the researchers say their findings give new insight into the origins of humans.
The first humans probably evolved near the South Africa-Namibia border before migrating north, the study says.
Published in the US journal Science, it aims to teach Africans on population history and aid research into why diseases hit particular groups.
The scientists examined genetic material from 121 African populations, as well as four African-American populations and 60 non-African populations.
The results provided "novel insights about levels and patterns of genetic diversity in Africa, a region that has been under-represented in human genetic studies", said Sarah Tishkoff, a geneticist from the University of Pennsylvania.
The first humans most likely evolved near the South Africa-Namibia border, the team said, and migrated north out of the continent via the Red Sea.
Researchers had identified 14 ancestral population clusters "that correlated with ethnicity and shared cultural and/or linguistic properties", they said.
They found high levels of mixed ancestry in most populations, as well as evidence showing common ancestry in geographically diverse groups.
The study also looked at African-American populations, finding that almost three-quarters could trace their ancestry to West Africa.
This knowledge could help experts better understand why certain diseases impact on African-American populations, researchers said.
Dr Tishkoff said that the goal was to "benefit Africans, both by learning more about their population history and by setting the stage for future genetic studies, including studies of genetic and environmental risk factors for disease and drug response".