A comment from a documentary about Rome stuck in my mind, it goes something like : "There is no history of Europe before Rome because for most of Europe, history starts with Rome conquering that region. They were the first to write anything down."

Similarly, we know how slavic peoples migrated into Europe because those regions stopped sending written updates back to Rome. Did they then revert back to pre-history? Or does a region continue to "have history" even if for a few centuries nobody in that area writes anything down?