A-Group, C-Group, Kerma) and other Afro-Asiatic speaking populations in Northeast Africa (Tigrean). However, the Egyptian groups were generally distinct from the sampled West and Central African populations. Among the samples included in the study is skeletal material from the , (from the Roman period) which clustered very closely with the Badarian series of the predynastic period. All the samples, particularly those of the Dynastic period, were significantly divergent from a neolithic West Saharan sample from Lower Nubia. Biological continuity was also found intact from the dynastic to the post-pharaonic periods. According to Irish:  Anthropologist Shomarka Keita takes issue with the suggestion of Irish that Egyptians and Nubians were not primary descendants of the African epipaleolithic and Neolithic populations. Keita also criticizes him for ignoring the possibility that the dentition of the ancient Egyptians could have been caused by "in situ microevolution" driven by dietary change, rather than by racial admixture. Eric Crubezy's team showed that Predynastic cemetery in Adaima in Upper Egypt showed "Khoisan" dental markers (formally referred to as "Bushmen canine")    The Ancient Egyptian language is classified into six major chronological divisions: Archaic Egyptian, Old Egyptian, Middle Egyptian, Late Egyptian, Demotic Egyptian and Coptic. The last was used as a working language until the 18th century AD. It is still used as a liturgical language by Egyptian Copts. The Ancient Egyptian language has been classified as a member of the Afroasiatic language family. There is no agreement on when and where these languages originated, though the language is generally believed to have originated somewhere in or near the region stretching from the Levant in the Near East to northern Kenya, and from the Eastern Sahara in North Africa to the Red Sea, or Southern Arabia, Ethiopia and Sudan. The language of the neighbouring Nubian people is one of the Nilo-Saharan languages, and is not one of the Afroasiatic languages.