Thomas Thompson reviews the generally accepted reason for the exagerated ages of certain patriarchs in his book "The Mythic Past". Here is a scan:
4 Techniques in writing Genesis
Genesis is a very good text to use when talking about how biblical narratives construct their pictures of the past. For example, three kinds of technical structures can be observed here. These three interrelated techniques are used to create coherence and unity in Genesis' 'history', in fact they offer the essence of Genesis' role as an account of the past. All are very important for the larger discussion. A naive or excessively realistic reading of Genesis can easily cause confusion about what is understood as historical by the tradition.
a) Chronologies The chronology that we find used in the book of Genesis in the Hebrew Bible is based on a very simple system, yet it has little to do with what we would normally understand as either chronology or history, and much more to do with highlighting and emphasizing the importance of events. The system is a construction based on a chronological scheme using the Hellenistic motif of a 'great year' of 4,000 years' duration. The history consists of a chain of traditions reaching back into the past, to a central event that is celebrated as the focus of the tradition's chronology. The projected completion of a 'great year' in the tradition's future allows the whole to be read as an implied prophecy. The identification of the great year's closure provides the hidden key to interpretation. The Hebrew Bible's great year finds its focal point in the year 2666 bce, the date of the Exodus and of the creation of old Israel. The great year of this tradition's future, the equivalent of the year 4,000, which marks the goal of this tradition, is timed to fall in 164 bce, the year in which the temple of Jerusalem was rededicated to Yahweh in the course of the Maccabean revolt. This is the year of the birth of the new Israel that gives meaning to the tradition. The key to this chronological revision of the stories is found in the implicit warning for the new departures that the temple's rededication inaugurates. The pivotal events on which the dating system is based, counting back from the Hellenistic period's Maccabean rededication of the temple, are: the edict of the Persian king Cyrus, who ordered the building of the second temple; the destruction of the first temple and the beginning of exile; the original construction of the temple by Solomon; the exodus of the Israelites from Egypt under Moses (marked with special emphasis); Yahweh's call of Abraham; and finally Abraham's birth. The whole begins with the creation of Adam in anno mundi (am) 1. The known historical information on the basis of which the system begins — that is from the viewpoint of the system's creators — was knowledge of the temple's rededication under the Maccabees (164 bce) and the length of time between that event and the date of the legendary edict of Cyrus (538 bce). This was 374 years, the exact length of time necessary to complete the needed total of a 'great year' of 4,000 years' duration since the beginning of the world. The pivotal date of the structure is the dating of the Exodus to the year 2666 am, representing both two-thirds of a 'great year' and 26 f of the Bible's forty generations, an average of 100 years' duration since the time of Adam. It is for this reason that the antediluvian patriarchs are given such great ages, up to Methuselah's 969 years. We find only a remnant of what appears to be a 100-year generation scheme in Genesis 15: 12-16, where the period of enslavement in Egypt is measured both as 400 years and as four generations long. A similar calculation is found in the frequent forty-year generation scheme in both the wilderness story, the Book of Judges and in the lives of some of Genesis' heroes. For example, Abraham lives for 100 years in Canaan. Isaac is born when Abraham is 100 years old. Isaac marries at the age of forty, and, at the age of sixty, has his first-born son Esau, who in his turn marries at the age of forty when Isaac is 100 years old. From the birth of Abraham in 1946 am to Solomon's temple in 3146 am, we have twelve generations totalling 1,200 years. Similarly we also have twelve generations, but of forty years each, totalling 480 years, from the Exodus to the building of the temple. From that time to the exile we have 430 years + 50 years for the exile itself, to find once again a paired time-span of 480 years. The 430-year period, from the building of the temple to its destruction, occurs again as the length of time from the entrance into Egypt to the exodus. The systemic quality of such calculations is assured when we note that the total length of the time of the patriarchs is exactly half of this total; i.e., 215 years long.
How the Bible talks about the past • 75
Adam...................................................................... 1 am
Birth of Abraham.............................................. 1946 am
Call of Abraham ............................................... 2021 am
Entrance into Egypt.......................................... 2236 am
Exodus from Egypt........................................... 2666 am
Solomon's temple.............................................. 3146 am
Exile to Babylon ............................................... 3576 am
Edict of Cyrus................................ 3626 am = 538 bce
Rededication of temple ................... 4000 am = 164 bce
All the data dependent on the 480-430-215 year scheme, as well as the date of the Exodus in the year 2666 and Abraham's birth in 1946, are explained within this Hellenistic ontology of time.