When one's family tree resembles a straight line - there is a clearly defined line running down to up but nothing much intersecting to provide movement to the left or right. This phenomenon is most commonly observed in eastern Utah and parts of the Deep South - those other pockets do exist.
Dude, welcome to Utah County, home of the Sister Wives. Hey, I might be a redneck, but even I'm not down with gene pool monopoly. Get me the hell out of this Truman Show.