I vaguely remember reading something similar once about an indigenous people in Brazil, the Tupis I think. It may have been in Jared Diamond's infamous book, but I'm not sure. I'm not sure how complex the book said their societies were either, but I think it was mentioned that they retained the use of royal titles and lineages from that earlier period.

Would this question fit in r/AskAnthropology better?
Edit: I accidentally sent this post three times, but I deleted the other two now.