Elsewhere/Where Else

One book, two stories, each connected to one another, giving the reader the choice of where to begin:

Joshua is a genetically-modified human, created to survive a 490-light-year voyage to another habitable planet after Earth is destroyed by a meteorite. He stumbles upon a genocidal plot among the elites of the ship, and somehow must find a way to survive using only his savant-like intellect.

Marai accompanies her mother on sabbatical to live among a lost tribe, when they encounter another murderous tribe who can see despite sewing their eyes closed. She learns of an ancient prophecy concerning her, and must use her power of belief to survive the impending doom.

How are the two stories connected? You might not know until you finish both