science

I was incautious with my phrasing, I should have said something like “humans have a singular capacity” etc. There may well be other storytelling species (in fact, I hope there are!) Whalesong seems like it could have the necessary complexity, for instance. I don't think crows warning each other about particular faces quite constitutes a story, though - that seems more like spreading "we hate that guy!" without any of the context a story would provide. Would be easy to check for storytelling with the species that can imitate speech, though.

I suspect this is a big part of what we're looking for when we're exploring personhood in nonhumans, too - whenever talking to animals, aliens, etc comes up in fiction, people inevitably end up swapping stories with them. Suggests to me that storytelling ability is what people are actually looking for.