Genetic History of East Africa

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Africa is thought to be the homeland of modern humans. Recent evidence has highlighted the importance of Eastern Africa (including Tanzania, Kenya, Ethiopia, and the Sudan) as a source region of modern human dispersals both within and out of Africa. Despite the important role of this region in human evolutionary history, very few populations have previously been studied for genetic variation. With National Science Foundation support, Dr. Sarah Tishkoff and an international team of colleagues will conduct one field season in southern Ethiopia to collect ~600 DNA samples obtained from blood, from 20 ethnically diverse populations. These will be added to a large collection of 5000 DNA samples from 80 ethnic groups throughout Africa, including 2000 samples from Tanzania, Kenya, and the Sudan. These newly collected DNA samples, together with ~500 previously collected East African samples, will be analyzed for genetic variation in the mitochondrial genome (inherited maternally), the Y chromosome (inherited paternally), and the nuclear genome (inherited through both parents). These data will be compared to data previously collected or published for these same markers in other African and non-African populations, in order to reconstruct the historical relationships of East African populations to each other and to other African populations, to reconstruct human demographic history (long-term effective population sizes, timing and extent of historic population expansions or contractions, levels of genetic exchange between populations), correlations between genetic and linguistic variation, and to test hypotheses of modern human origins. Intellectual merit: Currently, very little is known about genetic diversity in Africa as a whole, and in East Africa, in particular. An important contribution of this project will be the collection of large quantities of DNA from linguistically and ethnically diverse East African populations and the development of a large genetic database that will be a critical resource to test hypotheses about modern human origins and dispersal events. The DNA samples will be an important resource for genetics researchers for many years to come. Secondly, Tishkoff will be collecting novel data that will expand knowledge of African population history, in particular, and human evolutionary history, in general. The results will have important implications for understanding the origin and spread of modern humans within and out of Africa, the dynamics of population dispersal events and how these events are correlated with climatic changes. Thirdly, the data collected from this project will be made publicly available and will act as an important comparative database for geneticists doing research on other African, as well as non-African, populations. Lastly, knowledge of African population substructure will benefit biomedical studies that rely on knowledge of population demographic history for proper design and interpretation of disease mapping approaches.Broader impact: This project will provide important training opportunities for undergraduate and graduate students, as well as postdoctoral researchers, particularly from under-represented minority groups who are interested in studying African population history . An additional goal of this project is to train and support African collaborators and students so that they can initiate and conduct independent research projects. All collected DNA samples will be shared with African colleagues. This will allow African scientists to develop independent research projects using the collected samples. Second, African collaborators will share responsibility for generation of genetic typing data. Third, Tishkoff will participate in training African scientists in genetic research techniques both in Africa and in the U.S.