Ten generations, from you to over a thousand
By generation 6–8 (the mid-1700s), the tree demands 64–256 unique ancestors. Before railways, partnering was overwhelmingly local — parish records show median distances of around 5–10 miles between partners' birthplaces, with longer journeys rare. Your ancestors were drawn from a pool of a few hundred to a few thousand possible partners, not from the population of England. The same individual inevitably appears in multiple branches: the theoretical 2n folds back on itself, and the real count falls to perhaps 600–800 by generation 10. The more constrained the geography, the sharper the collapse.