"Well we have modern medicine now, too, but still managed without killing unfamiliar tribes literally every time they ran into each other before that. I mean, we had wars, but not that thoroughly."

"We didn't go around killing strangers of our own species in primitive times! Not if they looked healthy. And sick people often went somewhere isolated to kill themselves even before someone else could do it."

"Kin selection," speculates Cam, "for suicidality on sickness, which extends for some reason to suicidality on meeting other species... even though it would have to be one heck of a disease to jump the biosphere barrier."

"I'm not personally acquainted with the theories, but I think something like that is the explanation for why people kill themselves when they feel like they've been irretrievably befouled," says the assistant coordinator. "But the categorization of other sapient species as automatically filth is a separate thing. Ideological rather than biological."

"That's promising. How'd it get so widespread?"

"...It's very hard to go against societal consensus. The purity-keepers of thousands of years ago made a decision, and their decision became the standard for all of civilization."

"Why is it so hard to go against societal consensus?"

"Societal consensus is important. It's how quarantine procedures are decided. If people habitually rebelled against established rules, we would have all died before we ever got around to inventing vaccines."

"Okay... but why does your entire civilization pretty much have just one societal consensus?"

"I'm not a historian; I don't know how it came about. But once it was true, of course very few people were going to do what we did. We might even be the only planet where something like this happened."

"Only one I've found, though I haven't checked them all and one of them wanted eight days to set up a quarantine before talking to me."

"I expect they're worried about catching the contagion."

"Yes, I expect so. Is worrying about sprouting wings, which is not a disease, also ideological?"

"It's known that the wing contagion comes from the - Earth maze people, so treating it that way is an extension of treating outsiders as automatically unclean. But even if it weren't... I think unexpectedly growing new limbs would be very upsetting for most people."

"Well, I'd suggest doing it expectedly instead but somehow I don't think it'd help. Congratulations on not calling them filth creatures!"

Assistant Coordinator Sikyal Tegati makes an alien facial expression. "Thank you. If we understood how it worked, and if people were used to thinking of growing wings as normal, then maybe... but we don't and we aren't."

"There's the planet that wanted eight days... and the ongoing civil wars... and a handful of people who I extracted from a civil war to wait it out on Earth... and you guys. And the places I haven't checked. Do you suppose that from this starting point your society could learn to live with the idea? Because otherwise it's going to be very hard to humanely supervise you and I don't think leaving you unsupervised is the best plan for the next while as things settle out."

"This planet will be fine," they assert. "We succeeded in establishing a new consensus. Even if the wing contagion got loose here... we would have a hard time, but I don't think there would be many deaths. I don't know anything about how the rest of the planets are doing."

"Haven't been talking to them?"

"Someone might be checking the interplanetary communication devices, but it isn't me and I don't know what they're hearing."

...Cam produces transcripts of recorded conversations between this planet and other planets since the end of the world.

Nope.

"Well, if they have been they weren't recording. How do you anticipate that going? What if your societal consensus is outnumbered?"

"I've heard enough to believe we have by far the most stable and functioning society," they say. "If we're lucky, maybe more planets will decide to join our consensus."

"And if they don't?"