The largest-ever study on African genetics has determined that the ancestral origin of humans was probably located in southern Africa, near the South Africa-Namibia border, scientists said today.
African, American, and European researchers working in collaboration over ten years released their study of African genetic data, providing a library of new information on the continent which is thought to be the source of the oldest settlements of modern humans, said a news statement released by the University of Pennsylvania (Penn).
Sarah Tishkoff collects samples in Tanzania. Participants provided information about their ethnicity, language, parents, and grandparents.
Photo courtesy of Sarah Tishkoff
"The study demonstrates startling diversity on the continent, shared ancestry among geographically diverse groups and traces the origins of Africans and African Americans," the statement said. The research is published in the April 30 issue of the journal Science Express.
The yellow shaded area on the border of South Africa and Namibia is the likely ancestral birthplace of modern humans, researchers calculate. The arrow on the Red Sea indicates the likely point where modern humans first left Africa to colonize the rest of the world.
Map courtesy Google Earth
The research team said that its work demonstrated that there is more genetic diversity in Africa than anywhere else on earth.
They analyzed the DNA of more than 3,000 individuals--from 121 African populations, 4 African American populations and 60 non-African populations--to trace the genetic structure of Africans to 14 ancestral population clusters that correlated with ethnicity and shared cultural and/or linguistic properties.
Extrapolating the data, scientists were able to map ancient migrations of populations and determined that the exit point of modern humans out of Africa was near the middle of the Red Sea in East Africa, the news statement added. (See map above.)
Ancient Common Ancestry
"They also provide evidence for ancient common ancestry of geographically diverse hunter-gatherer populations in Africa, including Pygmies from central Africa and click-speaking populations from southern and eastern Africa, suggesting the possibility that the original pygmy language may have contained clicks. Overall, they demonstrate remarkable correspondence between cultural, linguistic, and genetic diversity in Africa."
"This is the largest study to date of African genetic diversity in the nuclear genome," said Sarah Tishkoff, a geneticist with joint appointments in the School of Arts and Sciences and the School of Medicine at the University of Pennsylvania.
"This long term collaboration, involving an international team of researchers and years of research expeditions to collect samples from populations living in remote regions of Africa, has resulted in novel insights about levels and patterns of genetic diversity in Africa, a region that has been underrepresented in human genetic studies.
"Our goal 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."
Hadza and Datog peoples listen to an explanation of the study in a village near Lake
Eyasi in the Arusha district of northern Tanzania.
Photo courtesy of Sarah Tishkoff
Tishkoff says that there is no single African population that is representative of the diversity present on the continent. Therefore, many ethnically diverse African populations should be included in studies of human genetic variation, disease susceptibility, and drug response.
Anthropologists, historians and linguists now have at their disposal a completely new volume of research with which to test theories of human migration, cultural evolution and population history in Africa, Penn said.
"Basic scientists, physicians and public health officials now have a foundation for illuminating the complex history of Africans and African-Americans, with implications for studies aimed at finding disease genes in these populations and learning which genetic differences make some individuals more susceptible to diseases like HIV, cancer or malaria."
African American Ancestry
The researchers said the study also sheds light on African American ancestry, which they find originates predominantly from western African Niger-Kordofanian (71 percent), European (13 percent), and other African (8 percent) populations, although admixture levels varied considerably among individuals.
These results could have important implications for the design and interpretation of studies which aim to identify genetic and environmental risk factors for diseases common in the African American community, including prostate cancer, hypertension and diabetes.
