Concerning contextualism and the question of human nature. It seems correct to say that speculation about the essence of human nature or the human species is limited by the contextual nature of the concepts involved: they are, fundamentally, concepts that we use to think about the world and about ourselves. So, it seems, it does not make much sense to ask whether these concepts still apply when we have evolved into something altogether different.
However, it would seem that even the latter conclusion might be too rash. It deals with a particular, and easy, situation: here are we, being what we are, and there are ‘they’, being altogether different. In such a situation, it seems indeed correct to say that the usual concepts no longer apply. But what about situations that are not so drastically different, but that represent more gradual differences? Thinking back: there must have been stages in our evolutionary history when language, thought, reason were somewhat different from what they are now. When did language become language-in-our-sense? That seems to be the wrong question to ask, it seems, at least if we think of it as a factual question that could be answered unequivocally. Think ahead: if we contemplate scenarios about cyborgs, brains implanted in machines, etc, then there, too, we are confronted with situations that defy a definite (positive or negative) answer to the question whether there is still a human nature, thinking, language.
So, it seems that not just the concepts, but also the very questions are contextual. This also indicates what is wrong with such considerations as Humboldt’s, who claims that we cannot consider the origin of language as a gradual process, since language constitutes reason and hence must be there as such, not piecemeal. That is a way of looking at it that has what little plausibility it has solely because it looks at the situation from the present perspective. But the point is that the fact that from the present perspective another perspective does not make sense, since it cannot be conceived in present terms, says nothing whatsoever about the other situation.