Characters don't need a Knowledge skill to know something about a particular field. Basic information should be covered by Common Knowledge assuming it makes sense within a character's background. A mercenary with a penchant for reading or a young history student, for example, doesn't necessarily need Knowledge (History). If tasked with a historical question, however, the two might roll normally while those without such a background roll at a penalty.
Savage Worlds Deluxe Edition p. 26