When the Sealand woman describes how human people used to be, it sounds like she is describing out world. This makes the story more believable.
While we might be skeptical that this story is taking place in the future, the Sealand woman’s descriptions of the former people and their limitations will sound familiar.
They were only ingenious half-humans, little better than savages; all living shut off from one another, with only clumsy words to link them. Often they were shut off still more by different languages, and different beliefs. (ch 14)
This is an interesting perspective on our people. We are described as only partially human, and limited by our words. It makes it sound like the development of thought-pictures was evolutionary, like language and writing. This makes the story more believable because we can picture this evolving for us.
Some of them could think individually, but they had to remain individuals. Emotions they could sometimes share, but they could not think collectively. (ch 14)
In a way, this makes sense. A society that could communicate on such an intimate level would be more advanced than ours. The reader will likely accept the story all the more because of this development. It also helps to explain how the Sealand people can swoop in to the rescue, and why some of David’s people are telepathic.