When did the Mabul (Deluge) occur? According to a simple reading of the genealogies recorded in Parashot Beresheet and Noah, respectively, the Mabul took place in the Hebrew year 1556 (i.e., 2204 BCE). An individual who is unfamiliar with the basics of history, Ancient Near East literature and geology will be unphased by this conclusion. For millenia, this was the conventional date assigned to the Flood, and for good reason - there was no evidence to suggest otherwise.
The findings of multiple branches of modern scholarship, however, have called this assumption into question on several grounds. From a geological perspective, for example, it seems certain that any cataclysmic flood that may have occurred in Mesopotamia would have taken place thousands of years earlier than the Torah indicates. Similarly, literature from other ancient cultures describes an event strikingly similar to the story of Noah, but seems to date it much earlier in history. This creates a problem for us: How can we accept the traditional dating of the Deluge when it appears to be contradicted by empirical evidence?
I would like to offer an answer to this problem that I believe to be correct, although I have not seen it mentioned in any contemporary Jewish articles on the subject. (A similar approach is alluded to in part by Kenneth Kitchen in The Reliability of the Old Testament).
Notice that the number of generations between Noah and Abraham is exactly ten. Similarly, the number of generations between Adam and Noah is ten. Finally, consider that the number of statements by which Hashem created the world is also ten. Coincidence? I think not.
It is quite reasonable to argue that the genealogies of Genesis and Noah are not exhaustive. They are summaries of the key "players" in the chain of generations, but do not make mention of every link in that chain. The number ten is chosen for its symbolic significance - it is reminiscent of the Creation of the World.
The emergence of Noah is, in a sense, the beginning of a new stage of "creation" after Adam. Thus, it is described as occurring after 10 generations. Similarly, the emergence of Abraham signifies the start of a new era of human history. It makes perfect sense that it should be characterized as the culmination of another 10 generations of human development.
Simply put, a list of ten generations can be understood as a symbolic summary of a genealogy that was in fact much longer. The summary is meant to convey an idea rather than transmit a comprehensive record of historical information.
There is further corroboration for this point from the Book of Ruth, which traces ten generations from Peretz, the son of Judah, down to King David. Many commentators point out that this genealogy stretches our credulity a bit, and that more than ten generations should have elapsed between the lifetimes of these two Biblical figures. Our solution resolves this problem beautifully as well. The ten generations described at the end of the Book of Ruth are not meant to provide an exhaustive list of David's ancestors. On the contrary, their purpose is to teach us that, with the birth of David, the evolution of Jewish leadership that began with Judah has reached a new plateau. A new chapter of Jewish history has been opened and, in what appears to be proper Biblical idiom, this is described as the culmination of a "ten step" process.
This approach allows a degree of flexibility in the interpretation of Biblical genealogy that renders many historical challenges to the Bible obsolete. We can no longer claim with certainty to know the years in which Adam was created or the Deluge occurred. However, we are thereby liberated from the need to "reconcile" the Biblical data with the conclusions of modern science.
This principle of interpreting genealogies of "ten" also explains a Mishnah in Pirke Avot:
"There were ten generations between Adam and Noah, to show God's patience in judgment; for all of those generations were angering Him, yet He waited before bringing the Flood upon them. There were ten generations between Noah and Abraham, to show God's patience in judgment, for all of those generations were angering Him until Abraham our forefather came and received the reward for all of them."
The Mishnah implies that the Torah's purpose in providing genealogies is not historical at all. If the Torah were an historical document, the Rabbis would not have commented on the "significance" of the number of generations between Adam, Noah and Abraham. This detail would have been viewed as an empirical fact like any other.
I believe that the Mishnah means to emphasize that the Torah's motive for presenting genealogies is not historical but philosophical. The Torah shows us that Hashem relates to us mercifully and tolerates our painstakingly slow spiritual progress. He allows us to advance at our own pace, even when He has every reason to expect much more of us.
Adam, Noah and Abraham each represent a distinct stage in the gradual development of mankind's relationship with God. The Torah teaches us that each of these transitions was a major achievement that was a long time in the making. This meant lengthy "Dark Ages" of primitivism, corruption and even paganism in the interim. Nevertheless, Hashem did not intervene until great human beings arose (i.e., Noah and Abraham, respectively) who were prepared to carry civilization along to the next level of enlightenment and growth.
These ideas are brought out by the genealogical record that separates these figures from one another by equal intervals of ten generations.
All in all, the interpretation of genealogies we have suggested underscores the fact that the Torah is a source of philosophical and ethical guidance, not a history book.
After writing this post, I found an interesting argument for this way of looking at Biblical genealogies here.