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.

If that were the case, then you would expect isolated groups of humans who never developed a writing system to be significantly different from "homo archivum", but we know that's not true.

We also know that groups without writing systems were historically able to adopt writing systems rather quickly, which is, I think, rather good evidence that writing is a technology, not a point of speciation.

Going back to Ancient Greece, Socrates didn't even believe in the effectiveness of writing for communication of knowledge. My poetry professor used to spend some time on this, because it's intimately tied to the art of poetry. He would cite a number of studies showing our emotional responses are intimately tied to our language processing, and that humans are wired to emotionally respond to, and remember, stories.

Even before writing, oral histories were passed down for many generations. For an extreme example, see: https://www.sapiens.org/language/oral-tradition/ .

I won't pretend to know what makes us human, but ultimately I believe it has to be rooted in something neurological, not technological.