So this question really got me to think deeper than I expected it to, because at first my mind went straight to animals, like dinosaurs or something dramatic like that but the more I sat with it, the more I realized what I would actually want to bring back is not a creature..

it is a way of life.. specifically, that whole sense of community that used to exist, especially growing up, where neighbours were basically family and everybody looked out for everybody without it being some big deal.
I remember hearing stories, and even experiencing bits of it myself growing up, where you could literally send your child to the neighbour's house to borrow salt or maggi, and nobody thought twice about it... Stories where if your parents weren't home, your neighbour could correct you, feed you, or even discipline you small and it was not seen as overstepping, it was seen as community doing what community is supposed to do... that kind of closeness, that kind of trust between people who were not even blood related, that is something I feel like has slowly gone extinct, especially with how individualistic everything has become now.
These days, everybody is so locked into their own world, their own business, their own four walls, that we have lost that natural instinct to check up on people just because, social media has made us connected in a weird surface way, but ironically, it's made real connection harder, People can watch your whole life through a screen and still not know how you are actually doing, that realness, that let me stop by and see how you are faring kind of energy, that's the thing I miss, and honestly, that is the thing I would bring back if I had that kind of power.
Why though?... Because I think a lot of what's wrong with how disconnected and lonely people feel today traces back to the erosion of that communal way of living.. back then, you didn't carry your burdens alone the way people do now, there was always someone close by who could either help you carry it or at least remind you that you weren't invisible... nowadays, people can be surrounded by hundreds of friends online and still feel like nobody would notice if they disappeared.. that is heavy and honestly kind of sad when you think about it.
If that sense of community came back, I feel like it would fix a lot more than people realize... not just loneliness, but even things like insecurity, crime, and that general everyone for themselves mentality that's taken over.. when people actually know and look out for each other, there's some kind of accountability that naturally exists, because you are not just a stranger to the person next door, you are someone they would actually notice if something happened to you.
So I wouldn't bring back an extinct animal or some old product as fun as that sounds, i would bring back that old way of living where people genuinely cared about people around them without needing a reason, because at the end of the day, no amount of technology or convenience can replace the feeling of actually being seen by the people around you.
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Its actually a very strong point that you have raised. I think communal living is strongly connected with rural lifestyle as soon as we started shifting to urban centers, we are becoming distant.