Exactly how old are the Greek texts we use to translate the works of Homer and Hesiod?
Although The Iliad and The Odyssey by Homer are assumed to date from the mid-eighth century BCE (750 BCE), the translations that we are accustomed to seeing today are taken from the earliest known complete manuscripts which are from the eleventh century CE. There are numerous fragments that date from the third century BCE and, from this fragmentary evidence, experts have come to believe that these epic poems were standardized during the rule of the Athenian tyrant, Pisistratus (Peisistratus), i.e. before 527 BCE. In antiquity, the texts were studied and preserved by the librarians of the Library of Alexandria (Egypt) and, due to the efforts of men like Zenodotus, Aristophanes of Byzantium and Aristarchus of Samothrake (Samothrace), we have our earliest commentary and criticism of Homer's poems.
Likewise, the extant poems of Hesiod are taken from manuscripts that date from the eleventh to the fourteenth century CE. The works of Hesiod are assumed to have come after Homer but the two poets are usually placed in the same century, i.e. the eighth century BCE. Like Homer, Hesiod's poems are assumed to have been passed down by some sort of oral tradition before they were committed to paper but that assumption is in no way certain. The length and complexity of the poems leads some researchers to assume that the poems were not passed down from generation to generation as an oral tradition but were written down at the time of their composition.
Let's consider the idea that these ancient poems were actually preserved by an oral tradition. If we choose some arbitrary dates to get a feel for the length of time involved, we might assume that the poems of Hesiod and Homer were composed in 750 BCE. Let's also assume that they were never written down but instead passed from poet to poet by word-of-mouth until 550 BCE, when they were finally committed to paper during the rule of the last tyrant of ancient Greece, Pisistratus. Assuming that each generation is approximately 25 years, that would mean that, in the intervening 200 years, the poems would have to pass through eight generations of poets. (The term generation is defined as the average time between the birth of a parent and the birth of their offspring.) Eight generations is a considerable period of time. There are people alive today who have memorized works far longer than The Iliad, so it is not impossible to believe that the poems of Homer and Hesiod were memorized in their entirety. However, to assume that every succeeding generation devotedly memorized the poems is a leap of faith that not everyone is willing to make.
Another problem also arises when we seriously consider the circumstances involved in the oral tradition hypothesis. It is easy to see in our modern age that artists, and creative people in general, tend to be a bit egotistical. I say this not as a condemnation but simply as an observation. How many times have you seen a movie that was supposedly based on a book and the only thing the movie and book had in common was the title? Usually the differences between the original book and the final screen version are dramatic and not subtle. Making a movie from a book can be viewed as retelling a story in much the same way the oral tradition perpetually retold the poems of Homer and Hesiod. The 2004 movie, Troy, might be used as a relevant example: in the movie, the ten year siege of Troy was reduced to a few days and noble, aristocratic characters like Menelaos (Menelaus) and Agamemnon were portrayed as medieval despots instead of charismatic leaders of nations. You have to ask yourself why the writers and producers of Troy would take a story that has been honored for 2500 years and change it to the point of butchery. The answer is simple: ego (or perhaps more politely, unbridled self expression). Were the storytellers of ancient Greece any different than their modern counterparts? I think not. I can easily imagine the ancient poets hearing the original Iliad and thinking to themselves that they could do better and then proceeding to add and subtract as they thought best.
Regardless of our well reasoned theories as to the origins of these ancient poems, we simply do not know their true genesis.
What we do know:
1) The poems of Homer and Hesiod were composed circa 750 BCE.
2) We know very little about the personal life of Hesiod and nothing about the life of Homer.
3) Fragments of the original poems of Homer and Hesiod date from the third century BCE but complete manuscripts date from no earlier than the eleventh century CE.