An odd hypothesis, I think. I don't think our ancestors were any less practical than us. Probably a great deal more practical, in fact.
You reference Plato, but you could easily phrase it in the other direction. "From Roman engineering to Wittgenstein blithering on about meaning."
> Now I place the concrete over everything else; theory is nice when it can illuminate why the practice works. Otherwise, it’s just words.
That mirrors the trajectory of all humankind, doesn’t it? From lofty Platonic ideals to nitty gritty empiricism and experimentation.