I was fascinated to see the world's longest family tree has been updated. The tree is the descendants of Confucius. Since Confucius died about 10 years before Socrates was born, this is an incredibly long time ago, almost 2,500 years. There's nothing in the western world to match it. As far as I'm aware the oldest tree in the west is for the intimately connected European royal families, who can be traced back to the Dark Ages but no further. I'm pretty sure there's no Roman whose descendants can be traced, and certainly no Greek. The reason the Confucius tree is known is his descendants were honoured and ennobled by successive generations of Emperors for so long that there are good records.

Of course, after 83 generations the amount of Confucius DNA in each of those people is a tiny fraction: 1 part in 2 ⁸³ in fact. Since the number of base pairs in human DNA is "only" about 3 billion, which is a mere 2 ³², that means the amount of surviving Confucius DNA is effectively zero for all but those of direct male lineage. They of course will have the same Y chromosome.