It is undeniable that these lineages are to some extent fictitious. There was no Pre-islamic science of genealogy, so that the first Muḥammadan investigators had only confused and scanty traditions to work on. They were biassed, moreover, by political, religious, and other considerations.[6] Thus their study of the Koran and of Biblical history led to the introduction of the patriarchs who stand at the head of their lists. Nor can we accept the national genealogy beginning with ‘Adnán as entirely historical, though a great deal of it was actually stored in the memories of the Arabs at the time when Islam arose, and is corroborated by the testimony of the Pre-islamic poets.[7] On the other hand, the alleged descent of every tribe from an eponymous ancestor is inconsistent with facts established by modern research.[8] It is probable that many names represent merely a local or accidental union; and many more, _e.g._, Ma‘add, seem originally to have denoted large groups or confederations of tribes. The theory of a radical difference between the Northern Arabs and those of the South, corresponding to the fierce hostility which has always divided them since the earliest days of Islam,[9] may hold good if we restrict the term 'Yemenite' (Southern) to the civilised Sabæans, Ḥimyarites, &c., who dwelt in Yemen and spoke their own dialect, but can hardly apply to the Arabic-speaking 'Yemenite' Bedouins scattered all over the peninsula. Such criticism, however, does not affect the value of the genealogical documents regarded as an index of the popular mind. From this point of view legend is often superior to fact, and it must be our aim in the following chapters to set forth what the Arabs believed rather than to examine whether or no they were justified in believing it. 'Arabic,' in its widest signification, has two principal dialects:-- 1. South Arabic, spoken in Yemen and including Sabæan, Ḥimyarite, Minæan, with the kindred dialects of Mahra and Shiḥr. 2. Arabic proper, spoken in Arabia generally, exclusive of Yemen. [Sidenote: South Arabic.]