The quote is:
But we should have been wary of answering back (to the questions of aliens), until we have develop a bit further. Meeting a more advanced civilisation (aliens from other planets), at our present stage (at the current stage of the human beings), might be a bit like the original inhabitants of America meeting Columbus. I don't think they were better off for it.
In the last sentence, does the pronoun "they" refer to all humans? or "original inhabitants of America"?