At least, syntactically encoded politeness.
So, I was working on the first section of my Colloquial Scottish textbook, and one of the first lessons involves learning how and when to use formal cases as opposed to informal ones. For instance, if you are speaking to a close friend, you would ask about their health by saying “Ciamar a tha thu?” (How are you?) But if you’re speaking to your professor, you say “Ciamar a tha sibh?” They mean the same thing, one’s just more formal. And a number of words and phrases have a formal and informal version. “Tapadh leibh” and “tapadh leat” both mean thank you, the former is simply more polite.
But that’s nothing new, I speak a bit of German, and the distinction exists there too. “Wie gehen sind Sie?” is the formal version of “Wie gehst du?” (How are you?) And Japanese has formal and informal ways of saying just about everything (though they use suffixes like -san (f) or -chan (i) attached to names rather than pronouns). What struck me as funny was that English doesn’t. So I got curious about how many languages lacked the distinction, it seemed to me it must be pretty rare. Except, according to the World Atlas of Language Structures (WALS) it isn’t rare at all. 136 Languages have no distinction at all, only 49 make a binary distinction, and a teeny tiny 22 use more distinctions or an entirely different system to differentiate.
And here’s where it gets really interesting. Of those 136 languages lacking a formality case, I recognized maybe nine. English is in there (probably because of our utter abandonment of cases after the Great Vowel Shift) and so is Irish Gaelic. The only other major language that makes the list is Hebrew, the rest are tribal languages and creoles. Things like Lakota, Hawaiian, Zulu, Maori, Egyptian. And the languages that do make a distinction? 90% of them are easily recognized. I could point to the geographic region they’re spoken in, unlike the formal-less group. They all come from well-populated and culturally advanced regions. Not just Indo-European either. Persian and Mandarin and Panjabi make the list. (The lists, by the way, are here if you’re interested. Now you can spot unlikely patterns in statistical data too!)
Now, I’m not saying that politeness develops with sociological advancement. I don’t know that the one causes the other, or vice versa. Probably not. It’s likely that the willingness and ability to bother with special phrasing in order to be nice is a side effect of more leisure time and less energy spent worrying about simply survival. And possibly a necessity as people began speaking to strangers on a more regular basis as cities expanded. But the correlation is really really interesting.