Genetic, archaeological, and paleoanthropological data indicate that all major migrations of anatomically modern Homo sapiens (AMHS) originated in Africa and recent data suggest that key dispersals emerged from Horn of Africa. Thus, Horn of Africa and neighboring regions on the Arabian Peninsula are critical to our understanding of the worldwide dispersal of humans out of Africa. There is a dearth of information available on key populations in this region, particularly in southern Arabia. The proposed study combines fieldwork, original laboratory and computational analyses, international collaborations, and innovative outreach programs to reconstruct population movements critical in the dispersal of humans. The project will provide powerful tests of the best current hypotheses of human migrations and generate new data to design future hypotheses. The project builds on past success in reconstructing simple migration histories (Europe and the New World) and serves as a model to determine the utility of genetic variation patterning and phylogenetic methods to reconstruct more complex migration histories. Eight hundred DNA samples from linguistically and geographically diverse populations in Eritrea (Horn of Africa) and Oman (southern Arabia) will be assayed for genetic variation across the mitochondrial genome and the Y chromosome. These data will be used to formulate new hypotheses as well as to test the following hypotheses: 1) a southern dispersal route out of Africa, 2) migration and back-migration between Horn of Africa and Arabia, and 3) expansion of the Semitic language family. Broader impact. 1) An important component of the proposed project is an expedition to collect blood samples in Eritrea (previously unsampled) and Oman (one published study). Genetics workshops will be taught in Eritrea and Oman and necessary laboratory equipment will be donated to each host institution. Aliquots of all collected samples will be shared with Eritrean and Omani colleagues. The proposed collaboration will allow African and Arabian collaborators to retain control of their own genetic resources as well as develop and direct independent research in the future. Eritrean colleagues have already developed a project to investigate resistance to malaria in Eritreans, a subject of national priority. 2) Furthermore, a unique program has been developed in which University of Florida journalism and communications graduate students will participate in University of Florida Department of Anthropology research projects in order to gain hands-on laboratory experience and create a media product for inclusion in their graduate portfolio. This program will have maximum impact because it provides training to the individuals charged with communicating current scientific research to the general public.