Starship

Starship by Brian W. Aldiss. paperback edition. ISBN: 9780380002269.

In the savage world of the Greene tribe, losing a woman was unforgivable, and Roy had lost his while hunting in the jungle called "the ponics". Disgraced, isolated, he joined the disreputable priest Marapper on a forbidden expedition through Deadways to find the legendary land of Forwards. They were to meet mutants, giants, regimented rats and telepathic rabbits, and the fabled Outsiders. Finally they would confront a secret kept hidden for 23 generations - a secret whose discovery would reveal their origins and destiny even as it destroyed their world!