Genetic ancestry and genealogical ancestry are not the same thing.
That's interesting. I see many well-meaning students of Scripture getting hung up on the word "generation" regarding Jesus' prophecy of the end times. It is my view that the word generation was not referring to the lifespan of a human, but rather an undisclosed "era" of conflict, which is at, or about, 2000 years.
exactly 4,000 years from Abraham to Jesus
I'm not following your timeframe here, but I do know that from Adam to Jesus exceeded 4000 years.
I've been working on a timeline of biblical chronology, which puts most OT books, and chapters within some books, as skewed and mixed up as the bulk of theological interpretation.
I used to see this 4000/2000 pattern; however, I have dismissed the idea of "exactly."
Your point is valid, regardless of accuracy. The switchover to the Gregorian calendar certainly created a disruption in comparing the biblical calendar with the system we are most oriented to.
Many people consider the creation of Adam as the start of the 4000 years, some count from the time of Seth's birth, some to Noah, and perhaps, "from Abraham" deserves a deeper look into how God set this pattern in history.
Thanks for that. I'll look into it, casually, at first, but I'll be able to determine the validity of that when I compare it to the patterns created by the years documented in the family generations and years mentioned in Scripture.