I am taking this to mean that you are asking if the elves/fairies/huldrefolk/etc. of Northern Europe are some sort of folk recollection of an ancient civilization. This is a fairly old notion, popular in various places in the nineteenth century. Folklorists generally do not regard this as a valid idea. Ireland, Britain, and Scandinavia (including the islands where Scandinavian languages were spoken) had a concept of supernatural beings living in social groups not unlike those of people. They tended to be slightly archaic in dress and other features, but they were really just a reflection of humanity. There is no reason to regard them as any sort of response to a previous indigenous people living in those areas. This is an excellent collection of essays dealing with studies of the fairy folk. If I have misunderstood your question, please let me know.