Parolin, Gianluca P. (2009). Citizenship in the Arab World: Kin, Religion and Nation-State. Amsterdam University Press. p. 30. ISBN978-9089640451. "The ‘arabicised or arabicising Arabs’, on the contrary, are believed to be the descendants of Ishmael through Adnan, but in this case the genealogy does not match the Biblical line exactly. The label ‘arabicised’ is due to the belief that Ishmael spoke Hebrew until he got to Mecca, where he married a Yemeni woman and learnt Arabic. Both genealogical lines go back to Sem, son of Noah, but only Adnanites can claim Abraham as their ascendant, and the lineage of Mohammed, the Seal of Prophets (khatim al-anbiya'), can therefore be traced back to Abraham. Contemporary historiography unveiled the lack of inner coherence of this genealogical system and demonstrated that it finds insufficient matching evidence; the distinction between Qahtanites and Adnanites is even believed to be a product of the Umayyad Age, when the war of factions (al-niza al-hizbi) was raging in the young Islamic Empire."
