I actually don't recall where I read that. It was one of the following 2 books: https://www.amazon.com/Sapiens-Humankind-Yuval-Noah-Harari/dp/0062316095 https:

I actually don't recall where I read that. It was one of the following 2 books: https://www.amazon.com/Sapiens-Humankind-Yuval-Noah-Harari/dp/0062316095 https://www.amazon.com/Sapiens-Humankind-Yuval-Noah-Harari/d... https://www.amazon.com/Tribe-Homecoming-Belonging-Sebastian-Junger/dp/144344958X https://www.amazon.com/Tribe-Homecoming-Belonging-Sebastian-... I wouldn't be surprised if the book derived that number from the link you gave either.