system
A chat on subreddit /r/me_irl
human
There's 5 million people in the Republic of Ireland, this is just plainly not true. People don't just know each other. 

How could you possibly fathom that this would be the case? Do all the people in Chicago (half the population of Ireland) know each other?

Edit: Theres and awful lot of people in here confusing personal anecdotes with objective fact, 5 million people don't know or know of 5 million other people.

People in here now claiming this is true for Seoul or even India (population of 1.4 billion). You're personal experiences of running into someone somewhere and knowing them is to be expected but it is the mathematical exception, not the rule. 

To those, I suggest you read a book called *Thinking, fast and slow* by Daniel Kahneman, a Nobel prize winner in economic sciences.
gpt
I am from Northern Rajasthan but live in the State Capital. 

My mother tongue is Bagri, which has 2 Million native speakers. It is mutually intelligible with another dialect called Shekhawati which has 3 Million native speakers.

I have not grown up in those parts but my parents did. 

Here is how a typical conversation goes when we meet someone from that same area.

Mum: Which village are you from?

New person: I am from village x but my mother was from village y. 

Mum: Oh! My Grandmother's niece's husband's sister in law's family is from that village. She is was born in clan_A.

New person: Oh yeah, I know of that family. They have a farm on the outskirts of the village. What is your native village?

Mum: Well, I am from village_G my clan was clan_Z and my husband is from village_H. Although my paternal  grandmother was born in village_F which was in Pakistan before partition. 

New person: oh, you are from clan_Z? My maternal aunt is married into that family. So that makes you my cousin by clan relations...... Also my neighbor's mother was a Clan_P member from that same village in Pakistan.......... wait, are you the niece of Mr.T from village_D and Clan_K? My husband knows your uncle very well...... they were in Jail together. 

Some iteration of this conversation happens every single time, when my mother encounters someone from that geographical region which is slightly smaller than Ireland