Antiquity attributed both poems to Homer, a blind poet variously located on Chios or Smyrna, about whom nothing is reliably known. From the eighteenth century scholars argued that the poems were composite, assembled from shorter lays. The decisive intervention came in the 1930s, when Milman Parry and his assistant Albert Lord went to Yugoslavia to record illiterate South Slavic singers performing long heroic songs. Parry had already shown that Homeric diction is systematically formulaic: fixed epithet-and-name combinations that fill particular metrical positions, arranged with great economy and little redundancy. The fieldwork showed living singers doing the same thing, composing in performance from a stock of formulas and typical scenes rather than reciting a memorised text.
That reframed the question. The poems are the product of an oral tradition of long standing, and their unusual composition is a technique, not a symptom of patchwork. It does not settle whether one poet gave each poem its final shape, and most scholars accept a monumental composer for each while disputing whether it was the same person. The Odyssey's language is slightly later than the Iliad's. The written fixing is usually placed in the eighth or seventh century BCE.
The texts were edited at Alexandria by Zenodotus, Aristophanes of Byzantium and Aristarchus, who compared manuscripts and marked suspect lines with critical signs. The division of each poem into twenty-four books, one per letter of the Greek alphabet, comes from this scholarship. The tenth-century Venetus A manuscript of the Iliad preserves, in dense marginal scholia, a great deal of that lost Alexandrian commentary.