called nyeenyo or neeno, and a servile category of slaves called jaam. Caste status has been hereditary, and endogamy among the men and women of a particular caste status has been an enduring feature among the Wolof people, states Leonardo Villalón – a professor of Political Science and African Studies. The Wolof's caste status, states Villalón, has been and is a greater barrier to inter-marriage than is either ethnicity or religion in Senegal. The castes have also been hierarchal, with lowest level being those of griots.Judith Irvine (1989), When Talk Isn't Cheap: Language and Political Economy, American Ethnologist, Vol. 16, No. 2 (May, 1989), pages 253-254 Their inherited inferiority has been culturally stated to be close to those of slaves (jaams or kaals). The castes, states David Gamble, were associated with ideas of relative purity-impurity. The leatherworkers, for example, were considered the lowest of the nyenyo because their occupation involving animal skins was considered dirty. Slaves have historically been a separate, endogamous group in the Wolof society. Slavery was either inherited by birth in the Wolof society, or were kidnapped, purchased as children from desperate parents during difficult times such as a famine, or slavery was imposed by the village elders as a punishment for offenses. By the early 18th-century, all sorts of charges and petty crimes resulted in the accused being punished to the slave strata. Slaves acquired by kidnapping, purchase or as captives of war were called jaam sayor in the Wolof society. The geer or "freeborn" too had a hierarchical structure. At the top were the royal rulers, below them were the regionally or locally powerful noble lineages who controlled territories and collected tribute, and below them were commoner freeborn called the baadoolo or "lacking power". Zarma people The Zarma people are an ethnic group predominantly found in westernmost Niger also found in significant numbers in the adjacent areas of Nigeria and Benin, along with smaller numbers in Burkina Faso, Ivory Coast and Ghana. The Zarma people are predominantly Muslims of the Maliki-Sunni school, and they live in the arid Sahel lands, along the Niger River valley which is a source of irrigation, forage for cattle herds, and drinking water. The Zarma people have had a history of slave and caste system, like many West African ethnic groups. The Zarma people have traditionally been a socially stratified society, like the Songhai people, featuring castes, state Jean-Pierre Olivier