What's the furthest back a person alive today could trace their ancestry (reliably)

[Northern_Piper]

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Is Julius Caesar's bloodline traceable to present day?

Of course for the average mortal I would never expect to be able to follow a genealogy that far back. But for someone whose lineage was considered as important as Caesar’s, one would think they would have made some effort to keep tracking it. So are the modern-day descendants of Julius Caesar (if any exist) known? And if not, when did they lose track of them? During the fall of Rome? Who was the last known descendant?