Study reveals African genetic diversity

Sarah Tishkoff, PIK professor, in Tanzania

Photo credit: Sarah Tishkoff
Geneticist Sarah Tishkoff (center) collects samples from a community in Tanzania.

Africa has long been thought to be the source of modern humans.

Now, a massive study led by a Penn researcher has determined that the ancestral origin of humans was likely located in the southern part of the continent, near the South Africa-Namibia border. The decade-long study also shows there is more diversity in Africa than anywhere else on earth.

“There’s not only a large amount of linguistic and cultural diversity, but also quite a bit of genetic diversity as well,” says Sarah Tishkoff, Penn’s David and Lyn Silfen University Associate Professor, and the study’s leader. “We’ve barely begun to skim the surface on how much diversity there is among African populations.”

Tishkoff led the collaboration of scientists from around the world. The effort generated the largest-ever study of African genetic data—more than 4 million genotypes. The results were published last month in the journal Science Express.

Researchers studied 121 African populations, four African-American populations and 60 non-African populations for patterns of genetic variation. Often, research teams had to visit remote places in order to collect samples from populations that had never before been studied.

The results have shown there is no single African population that represents diversity across the continent. Tishkoff, a Penn Integrates Knowledge Professor with appointments in the School of Arts and Sciences and the School of Medicine, says the research has revealed insights about a region that has been underrepresented in genetic studies.

Tishkoff is also keenly interested in how genotype correlates with phenotype and understanding genetic differences in things like taste perception and height.

“Our goal,” she says, “has been to do research that will 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.”

The study has excited researchers in numerous fields, says Tishkoff. Anthropologists, historians and linguists will be able to use the findings to test theories of human migration, cultural evolution and population history in Africa. Basic scientists, physicians and public health officials will be able to use the data to illuminate the history of Africans and African Americans in order to learn which genetic differences make some people more susceptible to HIV, cancer or malaria.

“It’s a data set that people will be looking at for years to come,” says Tishkoff. “It’s a one-time-only data set.”

Originally published on May 21, 2009