The Bible claims Jesus was a descendant of King David. Dr. Yan Wong shows that this is true ("all of Jesus's contemporaries" were as well), and repeats the geneological experiment for today's larger population:
How far do we have to go back to find the most recent common ancestor of all humans alive today? Again, estimates are remarkably short. Even taking account of distant isolation and local inbreeding, the quoted figures are 100 or so generations in the past: a mere 3,000 years ago. And one can, of course, project this model into the future, too. The maths tells us that in 3,000 years someone alive today will be the common ancestor of all humanity.