I knew a Chinese Computer Scientist who was treated with great deference by other Chinese academics because he was (or believed to be) a descendant of Confucius. He never made a big deal of it, but they all seemed to know it about him. Perhaps it was because of his last name.
He was an interesting man. He had a bad stutter, but gave excellent lectures with an overhead projector and slides with moving parts.
For Europe, there’s been a lot of people who have tried to go back to the Roman emperors and further. The term used is Descent from antiquity. As that article notes there’s a lot of conjectures but nothing considered proven. The gap is remarkably small, only a couple hundred years at most.
There’s a ton of people who have taken one of these conjectured lines and thrown it into their GEDCOM files. Some have even extended it further. Since one emperor was descended from Jewish royalty (they say), they then go back thru later Hebrew kings/high priests to Biblical genealogies which then takes them back to good old Adam and Eve. Okaaaay.
Mitochondria only relates to the direct female line. If there’s a man in the line of descent, all bets are off. What are the odds everyone’s G^200grandmother via maternal lines is that one lady or one of her maternal line? How far sepearted before we notice the mutations are too divergent?
So yes, odds are you can find that fellow somewhere in your line. I suppose the other point is it shows the newcomers (Romans, then Angles and Saxons, etc.) rather than pushing out and exterminating the locals, made party time with them.
Right, the mitochondrial match is interesting because it shows a subset of people related to Cheddar Man down the maternal line. But everyone is related to Cheddar Man down some line. Statistically it is vanishingly unlikely at that distance that he is not everyone’s ancestor. At around 5,000 years you reach a point of likely complete common ancestry, where it’s statistically likely that everyone then alive was either the ancestor of everyone alive today or of nobody. At Cheddar Man’s age of 12,000 years complete common ancestry becomes a virtual certainty.
ETA: on reflection of course it’s still possible that he’s nobody’s ancestor, because the mtDNA came from a shared female common ancestor, so all his descendants may have died out. So all we know for sure is that an unknown woman that the mtDNA came from is everybody’s ancestor; while he is either everyone’s ancestor or nobody’s.
This has probably been mentioned elsewhere in this thread but bears repeating: it may be noteworthy to be able to document descent from Charlemagne, but the mere fact of being one of Charlemagne’s descendants is not at all remarkable, because everyone with any European ancestry whatsoever is also one of his descendants.
A whole chapter is devoted to this is this book: A Brief History of Everyone Who Ever Lived: The Human Story Retold Through Our Genes
None of these people was alive in the 10th century.
In a 1987 column, Cecil noted that a UK resident born in 1947 had ancestors in 1200 covering 80% of the population at the time. He also discussed the concept of pedigree collapse, which is the idea that while one’s ancestors first grow exponentially the further you go back (2 parents, 4 grandparents, 8 great-grand parents, etc) eventually the same G^n grandparent takes more than one slot - you become related to them via more than one of their descendants. Go back to 1200 and the great majority (>70%) of your ancestors will be duplicates, with multiple lines of your tree tracing to them.
Before 1200, the number of ancestors in the example decrease the further you go back, along with the general population alive at the time.
I guess the real distinction here is statistics vs. traceability. As I said earlier, for most non-nobility, records in England appear to peter out sometime around the Civil War and the Restoration, when the Puritans were in charge and so the churches appear to be erratic and lax in record-keeping. I imagine on the continent, accumulated damage from assorted wars would have made some record retention spotty at times. (By contrast, I understand the Icelandic records are fairly reliable much further back).
Exactly. The thrust of the OP was about having reasonable records to document your family tree. Not probability or DNA.
apparently, the earliest verifiable ancestors we have were two brothers who managed to get to what would be Michigan/Indiana in the late 1600s. One either kidnapped or convinced one of the local Indian princesses to elope with him and move to what would become central Indiana which started out the branch of the family I’m part of …
How this was verified was a receipt of a payoff years later to settle the feud … apparently said princess was worth a side of beef and 2 kegs of beer…
What exactly is an Indian “Princess”? I don’t think there were any monarchies in the Michigan/Indiana area.
Indians come in only two types: Chiefs and Princesses.
Not senators? 
Most members the royal families of europe can trace back to Charlemagne, and his grandparents are known (with little chance of error… since they weren’t particularly famous )…
.
eg Jacquetta of Luxembourg - Wikipedia is traced back to Charlemagne,
and forward to King Henry VIII …
I’m Jewish. I can trace my ancestry to the people who immigrated to America, because my parents personally knew all of them. But I’m pretty sure the records before that have been lost or destroyed.