Imagine, my whole life (as I am 40 years old at present), isolated from the outside world, knowing only five other people, ever.
This family in Siberia was thus isolated, by choice, from the rest of the world. They escaped religious persecution, and even had no idea that World War II happened. The mom, dad, and four kids lived on what they could, growing crops, occasionally hunting, and living in famine or near famine conditions.
They were discovered first by a pilot and then by some geologists, who traveled to meet them. Their story is covered on the Smithsonian website, in a fascinating tale. It’s cultural study at its best. The article is a decently long read, but worth it if you have the time.