Bonobos use a kind of syntax once thought to be unique to humans

Reinforcing my strongly held belief that what fundamentally sets humans apart isn't spoken language, or tools, or any of that, but rather the fact we write down what we know, then make those writings available to future generations to build on. We're a species distinguished from all others by our information-archival and -dissemination practices. We're an archivist species, a librarian species. Homo archivum. In my opinion.

Writing is a new phenomenon. It's certainly a novel ability, but genetically we were around for a few million years before we even developed civilization, tens of thousands more before behavioral modernity, and only in the last 10k years have we developed writing. But other commenters have already said as much.

I would contest that what makes us unique is recursion as a general ability. In that sense, writing is a method of recursively building knowledge. But we also have it with spoken language, as we recursively build vocabulary and grammar into complex communication. We have it with tools, as we are the only species (at least as far as I know) that uses tools to make tools. We also seem to have it with our physical abilities: witness the constantly broken records in competition sports.