With our knowledge of modern-day genetics, we realize that it was possible for God to place the potential for all people throughout history into the genes of Adam and Eve when He created them.
I like the idea of the documentary as a portrait. There's not a chronological beginning, middle, and end structure. You build something in the editing room that's shaped by getting to know the person and digging deeper, unpeeling the layers of them as you get to know them.