Doubt

Another swarm has returned. It found a deep chasm, went inside, and observed many small animals, some that might be edible. A good discovery, but still not what we want to find. Another place without the Singer in it. This is discouraging progress.

(What if the Singer isn't in the world anymore?)

We didn't know how big the world could turn out to be. We once thought our wall was large, even after we came to the end of it. But now our swarms travel all over the plains, some on such long searches that the parts that go are many generations removed from the parts that come back. The world is unimaginably vast. And so empty.

(Where are the others the Singer spoke of? The Digger? The Spitter? The fast animals the voices eat? Has any swarm had to flee an evertoothed? Why is there nothing else living in the world but stinging bubbles?)

We can't have seen everything in the world yet. Every swarm comes to a point where it has learned all it can remember, and must come back. Each swarm after that can go a little farther, but still turns back while there is more in front of it.

(What will we do when there is no more world to find?)

If a time ever comes when there is no place a swarm can go that another swarm has not already been, then we'll know we have found the edges of the world. And if we haven't found the Singer by then...

(If the Singer left us...)

If we come to the end of the world and the Singer isn't there...we will be forced to stop looking.

(If there is no Singer, what is there?)

But this hasn't happened. We haven't found an end in any direction. We don't know that the world has an end, and we have no reason to give up before we have cause to think otherwise.

Time frame: ~20 million years in the past