how does travis explain the chain of cause and effect that he says would occur a hunter accidentaly killed even one mouse?

Travis insists that interrupting any of the natural processes in the past could have irreparable repercussions for the future. He draws out the example of killing one mouse and articulates the potential aftershocks of it: "Step on a mouse and you leave your print, like a Grand Canyon, across Eternity. Queen Elizabeth might never be born, Washington might not cross the Delaware, there might never be a United States at all" (4). Stepping on a mouse has a much broader reach than Eckels initially thought.