As the Definition of Man makes clear at the end of Chapter One, this novel invites us to enter a scary world which is a theocracy, and where any deviation of the norm, no matter how small or insignificant such as having a sixth toe, is ruthlessly punished and eradicated. As the story makes clear, babies that have a deviation are killed and adults that are found to have a deviation are sterilised and then expelled from the community of which they are a part to dwell on The Fringes with other deviants. Note how the adult Sophie, whom David meets once more in The Fringes at the end of the novel, comments about her fate and talks about her relationship with Gordon, David's uncle:
You've never known loneliness. You can't understand the awful emptiness that's waiting all round us here. I'd have given him babies glady, if I could... I--oh, why do they do that to us? Why didn't they kill me? It would have been kinder than this...
The fate of deviants then is clearly outlined in this example of ellipsis, where Sophie doesn't say everything she wants to say and leaves us to piece together her background and what happened to her when she was captured after her parents tried to flee with her when she was little.