Humans began to rapidly accumulate technological knowledge 600k years ago

The would strongly point to speech developing around that time, but there's no mention of language or speech in the article - odd.

What durable artifacts of either are presented in the article? It's paywalled, I haven't read the whole thing.

The common ancestor of neanderthals and homo sapiens had a larger than normal hole in the skull (the hypoglossal canal) which contains the nerve bundle going to the tongue. They're pretty sure that was the result of language use before 1M BC. There may have been several stages of later improvement after the initial development.

Yet some other evidence places it much later at around 130ky. Go figure.

It's unclear tech transfer is speech driven. People can read machines and reason about purpose without natural language. We've all learned tricks from undocumented code. I've learned mechanical tricks poking around scrap yards.

maybe unclear to you. may I recommend Orality and Literacy by Walter J. Ong. which talks about how text and writing transformed human culture

the point (which I learned from the book) is how writting transformed human culture but did not define it, humans have a pre-literal (i.e. written) culture whose origin is literally really lost to history

I'm saying that tech transfer can absolutely be speech driven, but I admit that text driven technological transfer is in some ways an improved version of oral-only cultural transmision (i.e. knowledge preservation)

No one is denying that tech transfer can be speech driven, but that doesn't mean that this particular increase in tech transfer was because of speech.

Right, but there are certainly going to be a ceiling to how far one can go. With writing it can be copied nearly verbatim and kept for centuries whereas the human mind is brittle and forgets, fuzzes, and randomly changes knowledge, it can contain only so much data.

That ceiling is pretty high above 18 steps for flint knapping.