The Seed of Earth

In a dark cave, on a cold planet, in a distant galaxy, four Earthmen sat and pondered the chance that had sent them there. The Computer had picked them to carry human civilization out beyond the limits of the Solar System. They were to be pioneers of a virgin world.
Four humans, imprisoned in a cave by alien raiders, awaiting an unknown fate, watching for the inevitable crackup that would hurl each at the others' throats —knowing that whatever they did would determine the future of their colony...