(NSFW) How far In a human Pedigree chart can one go back in time before humans stop doubling? What is the term where the change occurs?

For example a person typically has two parents, four grandparents, eight great grandparents, but what happens to the logic when ones linage exceeds the population of the planet at the time way way back? Does something have to break down and create duplicates? How far can anyone’s Pedigree Chart go before one is certain to have duplicate Pedigree members? What is the Genealogical term and typical historical date for this limit?