It seems that some form of bow from the polite nod to the self abnegating kowtow have existed in many times and places. Is this practice as widespread as it seems to me? If it is why and how? If not why does it seem that way?
You may obtain a better response from /r/Askanthropology since this question is more cultural/ethnographic than historical. That said, some here may be able to provide some historical insight into this practice.