Question - Jesus, the "Davidic Line", and Ancestry Calculations

[MadeUpName2]

Jesus’ descent from David sometimes comes up in apologetics discussions. Ancestry calculations may add a wrinkle to the debate.

Mathematicians calculate how far back you’d have to go before EVERYBODY in the past either had a line that died out, or is your ancestor. Everybody alive today is related to pretty much everybody else from mere thousands of years ago. So regardless of where you live, your ancestors probably included Indo-Europeans, ancient American hunters, and the guys who built Khufu’s pyramid.

Here’s a good video explaining this process:

David and his son Solomon both had numerous wives and concubines. The Bible states that Solomon alone had 700 wives and 300 concubines. Rehoboam had 18 wives and 60 concubines, with numerous children. Even from the perspective of a skeptic who doubts the Bible’s exact figures, a Near Eastern monarch from this period would be expected to have large numbers of wives, concubines, and children – Ramesses the Great being an excellent example. Additionally, they belonged to an ethnic group that might have practiced more endogamy (marriage within the group) than other Near Eastern societies. So you might expect the Davidic line to show up as common ancestors to other people in the region.

Would it be possible to run calculations to determine whether most – if not all – of the adult men in Judea during the first century belonged to David’s lineage? (Including Jesus.)

And if so, would such a calculation prove that Jesus belonged to the Davidic line? Or would this sort of calculation miss some crucial element of ancient Jewish or Christian succession rules?

 

[MPat]

Recently, mathematicians have calculated how far back you’d have to go before EVERYBODY in the past either had a line that died out, or is your ancestor.

Yes, starting from some obviously false assumptions.

All that shows is that anything can be derived from a falsehood.

Here’s a good video explaining this process:

One of the first places when it becomes obvious that assumptions are going to be false is about 1:38, when it is claimed that 30 generations ago each of us is going to have more than a billion of ancestors.

That’s about 30 * 25 = 750 years ago. So, about 1250. How many people were alive at that point? Wikipedia (https://en.wikipedia.org/w/index.php?title=World_population&oldid=896031034#Past_population) gives the estimate of 400 millions for year 1000 and 458 millions for year 1500. So, less than 1 billion.

The correct conclusion here is not that we share the same ancestors, but that those ancestors take more than one place in such family tree.

Then he goes to another false assumption of each parent being chosen independently…

Yes, with such assumptions one can “prove” anything.

If you drop those oversimplifying assumptions, no useful conclusion is going to be reached.

Would it be possible to run calculations to determine whether most – if not all – of the adult men in Judea during the first century belonged to David’s lineage? (Including Jesus.)

And if so, would such a calculation prove that Jesus belonged to the Davidic line?

No, if calculations are going to be anywhere near practically possible, they would be completely useless, for some significant simplifying assumptions would have to be made, invalidating everything.

 

[MadeUpName2]

The correct conclusion here is not that we share the same ancestors, but that those ancestors take more than one place in such family tree.

Then he goes to another false assumption of each parent being chosen independently…

Yes, with such assumptions one can “prove” anything.

Thanks for taking the time to answer. One quick note:

The toy models that he used to explain the idea indeed do ignore the things you mentioned.

The Nature paper that he cites, however, claims to model historical world population more realistically: Modelling the recent common ancestry of all living humans | Nature.

My guess is that this will not change your conclusion in light of the quoted text below, but I figured I’d mention it.

No, if calculations are going to be anywhere near practically possible, they would be completely useless, for some significant simplifying assumptions would have to be made, invalidating everything.

Are there any circumstances where this sort of descent modelling is workable for ancient / medieval / early modern history , or is it invalid across the entire stretch of time before modern government recordkeeping to trace descent?

In other words, would simplifying assumptions be less crippling or necessary if we talking about somewhere other than bronze / iron age Israel?