Our tapeworm-philosopher gets its teeth into the subject. Given that the human is so clearly designed to be hospitable to tapeworm-kind, then it follows that if there are more humans, other humans out there beyond the anus, then they, too, must be hospitable to tapeworm-kind. Tapeworm-kind has become aware of itself existing in the human; it is logical to assume that if other humans exist then there must be other tapeworms, and if travel between humans is possible -- and we infer that it might be, from the disappearance of our egg sacs through the anus of the human -- then sooner or later humans interacting in the broader universe might exchange eggs from these hypothetical alien tapeworms, in which case, visitors! Because the human was already here before we became self-aware, it clearly existed for a long time before us. So if there are many humans, there has been a lot of time for the alien tapeworm-visitors to reach us. So where are they?

[...] In reality, the human is unaware of the existence of the tapeworm. This would be a good thing, from the worm's point of view, if it had any grasp of the broader context of its existence: it ought by rights to be doing the wormy equivalent of hiding under the bed covers, gibbering in fear. [...] There are vast, ancient, alien intellects in the macrocosm beyond the well-known human, and they are unsympathetic to tapeworms. Intrepid tapeworm cosmonauts seeking to make their way beyond the anus and across the universe to colonize other humans are in for a rough ride indeed, for they are intimately evolved to thrive in one particular environment, and that environment (the mammalian gut) is sparsely distributed throughout the universe. Much of the cosmos is inherently hostile to tapeworms. This is why tapeworms have not, in fact, colonized the universe and converted all available biomass into a constantly spawning Gordian knot of Platyhelminthic life.

The comments are good, too:

• "Ringularity"
• "Arsetronaut"
• "Unbounded meta-gut"
• "Anuses all the way down"

Previously, previously, previously, previously, previously, previously, previously.