The Technology Levels of the World

Fantasy writers and people in general who are looking at history have a tendency to assume that people in ancient times had more simple ways of doing things. For example, natural gas as cooking fuel was used in ancient China back in like 3000 BC because they were drilling for salt. That is something that strikes you as a very modern kind of technology to have. And yet there they were. But I think it's a really good thing to remember that regardless of technology level or advancement in knowledge, people are not stupid.