It would be fun to have an activity that shows the furthest back your family tree could be traced, or your earliest ancestor.
If you or a relative has added your earliest known ancestors to Family Tree, you can go to the Landscape view and click away, generation by generation, along the different branches, until you discover your earliest known ancestor for yourself.
Alternatively, there are different Family Tree compatible progams (another user will no doubt be able to provide details) that can work this out for you.
The important thing to remember is the factor of "the furthest back your family tree could be traced" is dependent on the amount of research that has been carried out on the different branches of your tree to date. By next week, another person (possibly a distant relative) could find they could add a further few generations to your tree, so this is an issue you would have to keep under constant review.