What are three hints that david's world is unusual in the novel the chrysalids

1. Some people have special things about them that the majority refer to as 'Deviations'. For example: David can communicate through think-talking or telepathy. 

2. Some animals have two heads, or are unusual sizes. (Again, Deviations or Deviants) 

3. Their world is strange, the 'Old People' seem to have been what time we live in now when we had planes, and cars, etc. They seem to live extremely sheltered and cult-like lives.