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.

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

In terms of intelligence, yes, but in terms of what we've achieved then "technology" such as writing/archiving certainly has made a massive difference, else we'd be limited to what could be built by passing down oral history and skills passed from one generation to the next, much like Aboriginal Australians.

I suspect that the neurological (& vocal) differences that make us more intelligent than other apes are likely extremely few - more like "fine tuning" differences than anything major.

The question is whether or not cultures that had no writing systems were limited to the same level of intelligence and/or development that other primates exhibit.

Given that with exception of an interesting knot-encoded (Quipu) system for some period of the Inca empire, the entire human population of the Americas (at least 15-20% of the total human population) fits this description, the answer seems to be "no". These cultures built huge cities (among the largest in the world at the time), used sophisticated irrigation schemes, ceramics technology and more.