After the identical ancestors point, your set of ancestors no longer overlaps exactly with everyone else’s, but it still includes a lot of people. Before the identical ancestors point, your family tree resembles a braided stream. Only in the final millennium or so does it shrink to resemble a tree. Over this time, you probably add another 5 to 10 billion ancestors. All in all, your family tree likely includes 10 to 15 billion humans out of the 120 billion or so who have ever lived. That means that, under a modern calendar, 33 million of them have a birthday today. Unless it’s February 29.
