32.

Where late the sweet birds sang by Kate Wilhelm

An unspecified cataclysm has left the world sterile, so humans turn to cloning to reproduce. But they find that this brings up more problems than it solves as they find that their clones are not 'human' in the same way that they are. Far too short, I would have been happy to have been immersed in Wilhelm's world for at least 300 more pages, left me desperate to know more. Loved it.