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Vol. 324 no. 5930 pp. 1035-1044
DOI: 10.1126/science.1172257
  • Research Article

The Genetic Structure and History of Africans and African Americans

  1. Scott M. Williams18
  1. 1Department of Biology, University of Maryland, College Park, MD 20742, USA.
  2. 2Departments of Genetics and Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
  3. 3Independent researcher, Sharon, CT 06069, USA.
  4. 4Department of History, University of California, Los Angeles, CA 90095, USA.
  5. 5Dipartimento di Biologia ed Evoluzione, Università di Ferrara, 44100 Ferrara, Italy.
  6. 6UMR 208, IRD-MNHN, Musée de l’Homme, 75116 Paris, France.
  7. 7Ministère de la Recherche Scientifique et de l’Innovation, BP 1457, Yaoundé, Cameroon.
  8. 8Malaria Research and Training Center, University of Bamako, Bamako, Mali.
  9. 9Department of Molecular Biology, Institute of Endemic Diseases, University of Khartoum, 15-13 Khartoum, Sudan.
  10. 10Department of Pathology, Faculty of Health Sciences, University of Stellenbosch, Tygerberg 7505, South Africa.
  11. 11Department of Biochemistry, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.
  12. 12Departments of Genetics and Community and Family Medicine, Dartmouth Medical School, Lebanon, NH 03756, USA.
  13. 13Kenya Medical Research Institute, Center for Biotechnology Research and Development, 54840-00200 Nairobi, Kenya.
  14. 14Division of Human Genetics, Faculty of Health Sciences, University of Stellenbosch, Tygerberg 7505, South Africa.
  15. 15Laboratory of Genomic Diversity, National Cancer Institute, Frederick, MD 21702, USA.
  16. 16International Biomedical Research in Africa, Abuja, Nigeria.
  17. 17Marshfield Clinic Research Foundation, Marshfield, WI 54449, USA.
  18. 18Department of Molecular Physiology and Biophysics, Center for Human Genetics Research, Vanderbilt University, Nashville, TN 37232, USA.
  1. *To whom correspondence should be addressed. E-mail: tishkoff{at}


Africa is the source of all modern humans, but characterization of genetic variation and of relationships among populations across the continent has been enigmatic. We studied 121 African populations, four African American populations, and 60 non-African populations for patterns of variation at 1327 nuclear microsatellite and insertion/deletion markers. We identified 14 ancestral population clusters in Africa that correlate with self-described ethnicity and shared cultural and/or linguistic properties. We observed high levels of mixed ancestry in most populations, reflecting historical migration events across the continent. Our data also provide evidence for shared ancestry among geographically diverse hunter-gatherer populations (Khoesan speakers and Pygmies). The ancestry of African Americans is predominantly from Niger-Kordofanian (~71%), European (~13%), and other African (~8%) populations, although admixture levels varied considerably among individuals. This study helps tease apart the complex evolutionary history of Africans and African Americans, aiding both anthropological and genetic epidemiologic studies.

  • Present address: Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, 24306 Plön, Germany.

  • These authors contributed equally to this work.

  • § These authors contributed equally to this work.

  • || Present address: Department of Internal Medicine, Ohio State University, Columbus, OH 43210, USA.

  • Present address: Office of Research and Development, National Center for Computational Toxicology, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.

  • # Present address: College of Education, University of Maryland, College Park, MD 20742, USA.

  • Received for publication 13 February 2009.
  • Accepted for publication 17 April 2009.