For a modern European, how many centuries back before a decent %age of his....?

[kcguy]

I came across an unpublished academic paper years ago, in which the researchers used computer modelling to simulate ancestry.  On the Common Ancestors of All Living Humans

Quoting from Section 5.3 of the paper, "Figure 14 shows the corresponding ancestry for a randomly selected Norwegian. In this case, 92.3% of the ancestry in the year 5000BC is attributable to the 'country' in which the sim lives, in central Norway, and 96% to Scandinavia as a whole. . ."

[kcguy]

I misunderstood your question the first time.  Instead of "ancestry", you meant "ancestors", as distinct people.  I didn't catch that the first time.

This time, I'm intentionally going off on my own tangent.

Years ago, before the birth of Prince William, I bought a book on the prince's ancestry.  As might be expected, there was a lot of pedigree collapse--it mentions that there are 27 lines of descent from Mary, Queen of Scots--but there were also some ancestors from much further afield.  (Of course, this doesn't really answer your question, since royalty are a bit less likely to marry someone from merely the next village over.)

Anyhow, here are some of the proposed lineages:
* The queen's grandmother, Queen Mary, whose grandmother was a Hungarian noblewoman, was descended from the half-brother of Vlad the Impaler, and through him she was descended from Genghis Khan.
* The queen is descended from a 14th-century count of Savoy, whose wife was from the Byzantine imperial family.
* The queen is descended from a tenth-century Duke of Hungary, whose wife was a Khazar princess and whose father had led the Magyars to Europe from the Asian steppes.
* The queen is descended, through medieval Crusader kings and kings of Armenia, from a second century king of Parthia.
* The author theorizes that one of the queen's ancestors, a tenth-century Spanish nobleman, was descended from the Caliphs of Cordoba, and through them from Abd Shams, the great-granduncle of Mohammed.
* The author also theorizes that another of her ancestors, an eighth-century French nobleman, was actually a Jewish "king" from Baghdad and a descendant of King David.
* The queen's mother was descended from a colonial Virginian, whose great-grandson was George Washington and whose sister was an ancestor of Robert E. Lee.  (OK, this one isn't as exotic, but I don't normally think of Europeans as having American ancestors.)

[kcguy]

The problem with "every living autchthon Central European is a descendant of Charlemagne is that it doesn't take social status in account.

That's probably true.  Americans are used to thinking of English social mobility, but my impression is that Germany worked differently.

Most of England operated on the principle of primogeniture, so that the bulk of the family property went to the eldest son, and younger sons had to fend for themselves.  Similarly, titles of nobility followed the same principle, so that the eldest son of a baron would eventually become a baron himself, but the younger sons would remain commoners.  Because of this, it would become fairly easy for the youngest son of the youngest son of a English nobleman to fall into the middle class or lower.  (For example, Matthew Crawley on Downton Abbey.)

In contrast, my understanding of Germany was that property was much more likely to be divided among all sons.  I also believe that all sons of a German baron would be barons.  So I think the social barriers of marrying outside your class would be a bit more impenetrable than in England, where the social classes were a bit more informal.

At least that's my general impression, that it's much easier to be descended from the English upper classes than the German.