Evolutionary processes shaping genetic structure in Ethiopia and the Sudans

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Individuals sampled from across the world show great diversity in their DNA. However the primary features that lead to this diversity are poorly understood. For example, it is well-known that groups residing in close geographic proximity often have similar DNA patterns relative to groups residing further away, but what sorts of anthropological or topographical features best predict these similarities? Do rivers provide gateways for promoting interactions among different groups and thus lead to DNA exchange among these groups throughout history? Do natural features such as mountains provide a major barrier to such interactions, or is not sharing a language or religion a more important barrier? Have the important features that promote genetic diversity changed over time? The Federal Democratic Republic of Ethiopian, the Republic of Sudan, and the Republic of South Sudan show great cultural diversity, with for example over 100 different languages spoken and over 100 different ethnic groups living within. The history of many of these peoples are poorly understood, with historical records often incomplete or contradictory. Recent studies have shown that the DNA of these groups are also highly diverse. This DNA provides a powerful means of resolving historical inaccuracies, and identifying the aforementioned features that promote intermixing among the different groups that have shaped the genetic landscape of this region for tens of thousands of years. In this project, we will develop and apply new, state-of-the-art statistical methodology to a novel DNA collection consisting of samples from several hundred Ethiopian and Sudanese individuals. We will identify the features that have shaped the genetic diversity of this unique region of the world, identifying historical events where different ethnic groups within these regions exchanged DNA, as well as DNA contributions from sources outside the countries' borders. Some of this methodology has been successfully used recently to explore the history of the United Kingdom, a part of the world with considerably less cultural and genetic diversity (http://www.peopleofthebritishisles.org/). Elucidating the dynamics of how groups interact genetically will have great implications for understanding how gene flow persists among populations historically and today. Understanding the genetic structure of this diverse region will also help future researchers design sampling strategies for studies testing whether particular regions of the genome are associated with common phenotypes such as height or disease status. This region of east Africa is also vital for studying human origins, housing the earliest known human fossil remains that confirm a history going back approximately 200,000 years. It is well-established that modern humans first arose in sub-Saharan Africa, and it is believed that Ethiopia and the Sudans were the gateway for the initial migrations of peoples out of sub-Saharan Africa when colonizing the rest of the world. By careful comparison of the DNA of the groups from this region with those outside of sub-Saharan Africa, we may be able to infer the routes taken by these early explorers and map out precisely how the world was colonized by migrating humans.