The genealogy of Genesis 11: could Shem have met Abram, his grandson of 8 generations?

The dating of those in the genealogy of Genesis 11, including the possibility that greatgrandparents outlived their grandchildren’s children, intrigued me so much that I had to do the math. So I made a chart to find out exactly who would have outlived who. This chart is based on the assumption that no extra generations are skipped in the genealogy, which might have happened (e.g., Shem begetting (i.e., fathering) the father/ancestor of Arphaxad at 100 and not Arphaxad himself)). 

If we number the date of Arphaxad’s birth as 100, this is how the years work:

100	Shem begets Arphaxad (2 years after flood) + lives another 500 years	Shem dies in ‘600’
135	Arphaxad begets Shelah + lives another 403 years	Arphaxad dies in ‘538’
165	Shelah begets Eber + lives another 403 years	Shelah dies in ‘568’
199	Eber begets Peleg + lives another 430 years	Eber dies in ‘629’
229	Peleg begets Reu + lives another 209 years	Peleg dies in ‘438’
261	Reu begets Serug + lives another 207 years	Reu dies in ‘468’
291	Serug begets Nahor + lives another 200 years	Serug dies in ‘491’
320	Nahor begets Terah + lives another 119 years	Nahor dies in ‘439’
390	Terah becomes father of Abram; lives total of 205 years	Terah dies in ‘525’

On the basis of this calculation, Shem would still have been alive when Abram was born and when Nahor died. In fact, all of the first four generations outlive the next five. Only Eber outlives Shem, at least according to the numbers given. This gives a different impression (again) of Abram leaving his family – especially assuming others of the earlier generation also lived so long.

If we include Noah in the genealogy, he would have died in 448 (98 being the year that the flood ended, and he lived 350 more years after the flood). That means Peleg would have died before Noah did, despite Noah. What is more interesting is that Abram could have known Noah since Noah would still have been alive when he was born.