Atavism is a return to a previous way of doing, saying, or seeing things. It can be casual, like wearing retro clothing and listening to vinyl records, or committed, like living in a straw hut without electricity.
It makes sense that atavism comes from a Latin word meaning “forefather,” since it refers to a way of doing things like our ancestors did them. It’s often used negatively, though, to refer to behavior the speaker finds primitive or unacceptable. Atavists are often called "throwbacks." In biology, the term atavism or “evolutionary throwback” is used when animals are born with features that had disappeared, such as legs on a whale.