That tree's focused on only one person, Ben Stacy; his ancestors. The entire tree sounds a lot more connected:
> However, by the early 1960s, some members of the Fugate clan had begun to resent their cobalt-tinted skin. Not only did their skin mark them as different, but by that time, people had already begun to associate their skin color with the family’s history of inbreeding.
It’s called pedigree collapse. Your family tree grows exponentially to the second power with each generation. So a mere 50 generations ago, which is to say roughly 1000-1500 years ago, you had 1,125,899,906,842,624 slots in your family tree. Needless to say the vast majority of those slots don't have a unique person in them.
> However, by the early 1960s, some members of the Fugate clan had begun to resent their cobalt-tinted skin. Not only did their skin mark them as different, but by that time, people had already begun to associate their skin color with the family’s history of inbreeding.