H. Beam Piper 
Genesis [EPUB ebook] 

Was this ill-fated expedition the end of a proud, old race—or the beginning of a new one? There are strange gaps in our records of the past. We find traces of man-like things—but, suddenly, man appears, far too much developed to be the ‘next step’ in a well-linked chain of evolutionary evidence. Perhaps something like the events of this story furnishes the answer to the riddle. Aboard the ship, there was neither day nor night; the hours slipped gently by, as vistas of star-gemmed blackness slid across the visiscreens. For the crew, time had some meaning—one watch on duty and two off. But for the thousand-odd colonists, the men and women who were to be the spearhead of migration to a new and friendlier planet, it had none. They slept, and played, worked at such tasks as they could invent, and slept again, while the huge ship followed her plotted trajectory.
Kalvar Dard, the army officer who would lead them in their new home, had as little to do as any of his followers. The ship’s officers had all the responsibility for the voyage, and, for the first time in over five years, he had none at all. He was finding the unaccustomed idleness more wearying than the hectic work of loading the ship before the blastoff from Doorsha. He went over his landing and security plans again, and found no probable emergency unprepared for. Dard wandered about the ship, talking to groups of his colonists, and found morale even better than he had hoped. He spent hours staring into the forward visiscreens, watching the disc of Tareesh, the planet of his destination, grow larger and plainer ahead…