1) Human progress arises from the development and improved use of tools/technology (and I'm including concepts like "if", as well as skills, as kinds of technology)
2) Our tool use abilities interact multiplicatively/geometrically. E.g., [what I can do with a hammer and a shovel] is not the sum of the [things I can do with hammers] and [the things I can do with shovels]
3) Our tool-use-abilities started meagre
4) Tool use is not uniquely human, but humans are better at it
5) Accidents of history and human development have allowed for the accumulation of tools (agriculture, e.g.)
... this "explanation" (or what have you) yields exponential growth curves that, I propose, would look very similar to those of humans. If there was a "tipping point" perhaps it was (5) -- the introduction of some substrate upon which cultural knowledge could grow.
Why do we take as the default hypothesis that language is, as you seem to be implying, a monolithic "thing"?
A more plausible hypothesis seems to me to be that language itself is constituted by a suite of cultural tools/skills. A language with a very limited vocabulary (especially one restricted to largely unhelpful words, e.g. "Justin Bieber", or "toe wart") is much weaker than one that has benefited from decades of cultural and generational digestion and iteration (i.e., a language that includes concepts like "however", or "on the condition that", or "art", or "gravity").
Proposal:
1) Human progress arises from the development and improved use of tools/technology (and I'm including concepts like "if", as well as skills, as kinds of technology)
2) Our tool use abilities interact multiplicatively/geometrically. E.g., [what I can do with a hammer and a shovel] is not the sum of the [things I can do with hammers] and [the things I can do with shovels]
3) Our tool-use-abilities started meagre
4) Tool use is not uniquely human, but humans are better at it
5) Accidents of history and human development have allowed for the accumulation of tools (agriculture, e.g.)
... this "explanation" (or what have you) yields exponential growth curves that, I propose, would look very similar to those of humans. If there was a "tipping point" perhaps it was (5) -- the introduction of some substrate upon which cultural knowledge could grow.