Here is the Bible's guidance for reading the genealogies of Genesis 4-5.
- The people mentioned are real, literal, historical people.
- Their actual ages are not important; what is important is that they all died.
- We are not given any indication that we are supposed to treat the genealogies as a means of calculating the age of the earth. No passage of the Bible does this or even hints at it.
- We are not given any indication that we are supposed to treat all the ages as strictly literal. No passage of the Bible does this or even hints at it; even when the genealogies are cited at length, the ages are deliberately omitted.
At a bare minimum, we should treat the genealogies the way the Bible does. For more detail, we should look closely at two points of data which provide interpretive context.
The fact that in these genealogies the emphasis is not on the long lifespans, but on the consistently repeated phrase "and he died". This is radically different from similar genealogies in the Ancient Near East.
The fact that two similar genealogies in the Ancient Near East. Mesopotamian literature also contains records of people with very long lifespans, far longer in fact than those in Genesis 4-5. The Sumerian King List (dating to at least 2,000 BCE), and the account called Rulers of Lagaš (c. 2000 BCE), record kings who reigned for thousands or even tens of thousands of years. However, the context in which these ages are found, it is clear they were not intended to be taken literally.
Let's look at this second point in particular. In the Sumerian King List, En-me-barage-si is said to have ruled for 900 years. His historicity is established by epigraphical evidence, so we know he was a real historical figure. This also means that scribes recording the lives of the kings, were contemporary with En-me-barage-si and knew that he did not literally rule 900 years. There is no epigraphical evidence that people in his day believed he had ruled for centuries; the earliest attribution of a 900 year reign dates to around 600 years after his kingship. As a side note, you can see that historians accept the historicity of En-me-barage-si even though he is said to have ruled for 900 years. Likewise, Gilgamesh is considered a historical figure despite having supposedly reigned for 125 years.
There are other patterns in the Sumerian King List which indicate the numbers are symbolic. In the earliest stage of the king list, rulers reign for up to 43,000 years. Then "the flood swept over", and the next section of the king list describes kings with reigns which are drastically shorter; still centuries long (even over 1,000 years), but on average less than one tenth the length of previous reigns. In a later section, the reigns become much shorter still; down to less than 500 years. Later again, the reigns drop massively, down to less than 100 years, and typically less than 30. Each reduction in the pattern of reign lengths, is preceded by a change of kingship from one city state to another.
So when the city state of Eridug rules, the reigns are tens of thousands of years, when the city state of Kish rules the reigns are rarely over 1,000 years, when the city state of Ur rules the reigns are less than 100 years. The length of rulership is associated with a gradual declining glory of the empire, and indicative of the strength of the prevailing city state. Interestingly, when the when the city state of Kish ruled for the first time the reigns are centuries long though rarely over 1,000 years, but when the city state of Kish ruled for the second time, the reigns are much shorter, less than 500 years. This indicates that the second time Kish ruled, the city state had declined greatly in power and glory.
Another indication that the reigns were not taken literally, is the way in which they are treated by other Sumerian texts. For example, a list extremely similar to the Sumerian King List, was produced by the city state of Lagash. This list, called the Rulers of Lagash, was actually written not as a sober historical document, but was written specifically as a parody of the Sumerian King List, an expression of the feud which Lagash had with the other city states. The Rulers of Lagash is intended to ridicule the Sumerian King List. But a superficial reading of the text does not reveal this. Here's an excerpt from the Rulers of Lagash.
164-172En-entar-zid: his god was Mes-an-du (?), of the seed of ancient days, who had grown together with the city, he acted for 990 years. ......, the son of En-entar-zid: he dug the canal Urmah-banda, and the canal Tabta-kug-jal, his personal god was Mes-an-du (?); his master Nin-jirsu commanded him to build his temple; he acted for 960 years.
173-175En-Enlile-su: he acted for 600 years. ......, the son of En-Enlile-su: his personal god was Ninazu; he acted for 660 years.
176......: he acted for 1110 years.
177-181Puzur-Ninlil: he acted for X x 60 + 1 years. En-Mes-an-du (?), the son of Puzur-Ninlil: his personal god was ......, he acted for 120 years. Dadu, the son of En-Mes-an-du (?): he acted for 160 years. Tuggur, the son of Dadu: he acted for 160 years.
182......: he acted for 120 years.
183-191Puzur-Mama, the scribe of Ninki: his personal god was Zazaru; he acted for ...... years. Lamku-nijgena (?), the administrator of Puzur-Mama, who built the wall of Jirsu, his ......, and the Tirac palace in Lagac: he acted for 280 years. Henjal, the son of Lamku-nijgena (?): his god was Pabilsaj (?), he acted for 140 years. ......, the son of Henjal: he acted for 144 years.
192-199Ur-Ninmarki, the scribe and scholar: ......, his personal gods were Haya and Nisaba, he acted for X + 20 years. Ur-Ninjirsu, the son of Ur-Ninmarki: he acted for X x 60 years. Ur-Bau, the scribe of Ur-Ninjirsu, who ...... in the assembly: he acted for X + 30 years. Gudea, the younger brother of Ur-Bau, ......, who was not the son of his mother nor the son of his father: he acted for ...... years.
200Written in the school. Nisaba be praised!
To us that might look like a formal, straightforward, genealogy including ages. To the original audience it was a very obvious parody which was never intended to be read literally. It was political satire for a very specific purpose.
Genealogies and rulership records could have social, historical, political, theological, and even cosmological significance. They were very important documents. In the case of the Rulers of Lagash record, the parody is identified by comparing the list with the original Sumerian King List. The conflict between Lagash and the other city states is revealed by the fact that the original Sumerian King List does not include Lagash. It has been deliberately omitted. Lagash was a city state which ruled itself independently, and fought with the Akkadian city states (such as Kish), until it was overcome by the Akkadian empire. It exclusion from the list is intended to reinforce its lack of status, even though some of the kings of Lagash had actually been prominent rulers of Sumer.
To omit Lagash from the Sumerian King List was a shocking and brutal reinforcement of its conquest; erased from the cosmos, Lagash is no longer a wealthy and significant city state which fought repeatedly for its independence, it no longer exists. In turn, when the scribes of Lagash re-wrote the Sumerian King List, they deliberately omitted certain of the Sumerian kings, and gave Lagash prominence instead. This is a political feud being waged by the scribal elite, and known only to the highest levels of the aristocracy.
An interesting point about the Rulers of Lagash is that it opens with the description of a golden age in which people lived up to two hundred years. However, it then blithely goes on to speak of kings who ruled over 1,000 years. There is no contradiction here, because the immensely long reigns of the kings were not intended to be understood as literal.
In fact even the two hundred year lifespan is described in formulaic, representative terms which were very likely understood non-literally; "in those days, the carefree youth of man lasted for 100 years and, following his upbringing, he lasted for another 100 years". This is to say "In those days the carefree youth of a man was many years, and his subsequent life many more years". The Egyptians did the same. For them the ideal lifespan was 120 years, but this was achieved only by the most noble, upright, or deserving, so that "a man of 120 years" (no matter how long he actually lived), was understood as a man of great character and worth.