After a certain point, actual records become scarce. In the absence of a will or land deed transfer, there may be none to prove lineage.
No offense intended but
1. My ancestors were slaves in Alabama and Mississippi. I can't go back further than 1870
2.Jewish children who survived the Holocaust sometimes couldn't remember who their grandparents were. And the Nazis made a concerted effort to destroy the synagogues and temples and the records that were in them.
3. Those of you who can go back and back and back are very fortunate but at some point, all things end.