In the process of adaptation of humans to their environment, positive or adaptive selection has played a main role. Positive selection has, however, been under-studied in African populations, despite their diversity and importance for understanding human history. Here, we have used 119 available whole-genome sequences from five Ethiopian populations (Amhara, Oromo, Somali, Wolayta and Gumuz) to investigate the modes and targets of positive selection in this part of the world. The site frequency spectrum-based test SFselect was applied to idfentify a wide range of events of selection (old and recent), and the haplotype-based statistic integrated haplotype score to detect more recent events, in each case with evaluation of the significance of candidate signals by extensive simulations. Additional insights were provided by considering admixture proportions and functional categories of genes. We identified both individual loci that are likely targets of classic sweeps and groups of genes that may have experienced polygenic adaptation. We found population-specific as well as shared signals of selection, with folate metabolism and the related ultraviolet response and skin pigmentation standing out as a shared pathway, perhaps as a response to the high levels of ultraviolet irradiation, and in addition strong signals in genes such as IFNA, MRC1, immunoglobulins and T-cell receptors which contribute to defend against pathogens. Signals of positive selection were detected in Ethiopian populations revealing novel adaptations in East Africa, and abundant targets for functional follow-up.

中文翻译：

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埃塞俄比亚混合种群的正向选择

在人类适应环境的过程中，积极或适应性选择发挥了主要作用。然而，尽管非洲人口具有多样性并且对于理解人类历史很重要，但积极选择在非洲人口中的研究还不够。在这里，我们使用了来自五个埃塞俄比亚人群（阿姆哈拉人、奥罗莫人、索马里人、沃莱塔人和古穆兹人）的 119 个可用全基因组序列来研究世界这一地区正选择的模式和目标。基于位点频谱的测试 SFselect 用于识别广泛的选择事件（旧的和最近的），基于单倍型的统计综合单倍型评分用于检测更多最近的事件，在每种情况下都评估候选的显着性通过广泛的模拟信号。通过考虑基因的混合比例和功能类别，提供了额外的见解。我们确定了可能是经典扫描目标的单个基因座和可能经历多基因适应的基因组。我们发现特定人群以及共同的选择信号，其中叶酸代谢和相关的紫外线反应和皮肤色素沉着作为共同途径脱颖而出，可能是对高水平紫外线照射的反应，此外还有基因中的强烈信号例如 IFNA、MRC1、免疫球蛋白和 T 细胞受体，有助于防御病原体。在埃塞俄比亚人群中检测到的正选择信号揭示了东非的新适应，以及丰富的功能性后续目标。