This is especially surprising because the common idea is that civilization arrived later into northern, colder Europe. Bushcraft like on the wonderful Primitive Technology youtube channel is harder when you don't have a year-round growing period. You need not just warmer clothes, but ways to stockpile and preserve food. Traditional Polish cuisine has many ways - preserves in glass jars, salt, pickling... Actually the cuisine is the aspect that positively surprises visitors the most. So many peoples and empires were present in the region, so many culinary influences. It's only lacking in saltwater fish because historically there was limited sea access.
Maybe the climate was different?