Post-Parshah Point: Noach
Over the past two Shabbosim, respectively, the Torah portion has given a precise accounting of each oldest son in the generations between Adam and Noah (Gen 5:3-31) and between Noah and Abraham (11:10-32). Quite noteworthy is the protracted lifespans of each person listed. According to some views, only these specific generational leaders were granted such extraordinary longevity; the rest of humanity - i.e., the "other sons and daughters" indicated for each father - lived more or less typical lifespans.
Be that as may, even within the few individuals listed, there are some interesting patterns. The first group, from Adam up to and including Noah, generally lived into the 900+ age range. The exceptions are Chanoch, whom the Torah makes a point of saying was taken by God well before his time (5:24), and Lamech, Noah's father, who still made it to the age of 777, and passed away just a few years before the Flood. Presumably he was granted a peaceful death a bit prematurely so as not to be swept away in the collective punishment of the generation.
But then, starting with Noah's son Shem - that is, starting with the first generation to live post-deluge - we see a drastic change. Shem himself, who spanned both eras, lived an even 600 years. This is significantly shorter than his fathers, though still longer than the next three generations, all of whom died in their mid-400s. In other words, we see a greater than 50% drop in lifespan after the Flood.
An ingenious theory I heard long ago was that this diminishment was caused by humanity's post-diluvian change from a vegetarian to a carnivorous diet - as indicated in 9:3. Of course, as a devoted carnivore myself, one who barely makes it through the Nine Days each year, I don't approve of this pshat, but I still can admit that it's clever!
Now we come to the 5th generation after Noah - Peleg, he who "b'yamav nifliga ha'aretz", "in whose days the earth was divided" (10:25) - a reference to the Tower of Babel. As I posted two years ago, God's response to the Tower of Babel rebellion was to create what we now call diversity, both linguistically and geographically as the Torah states, and in my opinion, racially and biologically (zoologically) as well. The earth was truly nifliga then, in a very comprehensive manner - it became the separated, fragmented, divisive place that it unfortunately still remains today.
But we also see, starting with Peleg, that this "division" occurred in a mathematical sense as well. Peleg lived a mere 209 years, and the remaining generations between him and Abraham all (with one exception) died in their 200s as well. Thus, in a very literal sense, the lifespan of humanity, or at least its leaders, was "nifliga" - cut in half - after the dispersion.
The exception to the consistent 2xx-year lifespans of this group is Abraham's grandfather, Nachor, who died "young" the age of 148. It is interesting to note that Terach, Abraham's father and the son of this Nachor, named one of his own sons "Nachor" after his father. If you look at the dating given in 11:24-26, it becomes clear that Terach gave his son Nachor this name while his father Nachor was still alive! As far as I know, this is the only case in the Bible of a child being named for a living relative. And that relative then died about 50 years later, or at least 50 years earlier than expected. That is, his remaining lifespan, after receiving the "honor" of having a grandson named for him, was cut in half!
I wonder if this is the ultimate source for Ashkenazic Jewry's taboo against naming children for living relatives?