Gallabat slave markets at Ethiopia–Sudan border, as well as the Massawa and Tajura markets on the Red Sea. Somali people The Somalis are an ethnic group of between 15 and 20 million people, constituting the largest ethnicity in Somalia, many of whom also live in Ethiopia, Kenya, and Djibouti. They have historically exhibited social stratification that has included embedded castes referred to as Higal (or Higalki, Argobba). The upper noble strata has been called Gob (or Asha), while the lower servile strata have been referred to as Sáb. The three main Somali castes are called Tumal (sometimes spelled Tomal), Midgan and Yibir (sometimes spelled Yebir). These fell outside of the traditional clan structure. The castes have been endogamous, a person born into it inherited its occupation. The Midgan have been the hunters, Tumal were the smiths, pottery and leatherworking caste, and the Yibir have been the saddle and prayer mat makers and magician caste., Quote: "Many of these items were not made by nomads but by a caste of artisans called the Saab, considered subservient (...) The Yebir, also members of the Saab caste, were responsible for crafting amulets (hardas), prayer mats, and saddles, and for performing rituals designed to protect nomads from snakes and scorpions, illnesses and harm during marriage and childbirth". Below the castes have been the Somali Bantus Jareer community, and these have been descendants of former slaves, including those who were runaway and emancipated slaves. According to Mohamed Eno and Abdi Kusow, the Somali caste communities are ethnically indistinguishable from each other, but upper castes have stigmatized the lower ones with mythical narratives such as they being of unholy origins or being engaged in dirty occupations. The four strata social system – high lineage, low lineage, caste groups and slaves – found among the Somalis has been common in the Horn of Africa region, states Donald Levine, and is also found among ethnic groups such as Afar, Amhara, Borana, Leqa, Sidamo, Kefa, Janjero and other peoples. According to Catherine Besteman - a professor of Anthropology, the widespread purchase of non-Somali African slaves during the medieval age helped structure the complex status hierarchy among the Somalis. However, adds Besteman, the Somali people from the upper strata have also been egalitarian in matters of clan leadership, while they have included concepts of social status, inferiority and exclusion of Sáb and slaves. In the northern regions where Somalis are