Answer:
It hints to the reader that unexpected changes in the Time Traveller's view may follow.
Step-by-step explanation:
In these lines, the author tells us that he has found some ruins, and that he is wondering the reason for these to be uninhabited. He concludes that the most likely answer is that people had wanted to control the population and their numbers had diminished too much. He explains that this solution was simple, but also wrong. The fact that the hypothesis is wrong means that he will most likely change his mind very soon.