This very interesting question helps us understand how consciousness was formed. Let's start with the second part of your question: « Could the ancestor of the man hear himself thinking? ». Language is not the very process of forming thought. It is a translation. read more
Of course, Grandin has language, and knows how to use it, so it is hard to say how much of her thinking has been influenced by it, but it is not unimaginable—and probably likely—that there are people who lack the ability to use language and think in the way she describes. read more