The stories that have come down to us as Norse myths developed throughout Northern Europe as part of an oral tradition dating from the eighth to the eleventh centuries. The forms of the tales we have today come from the earliest extant manuscripts, dating to the thirteenth century. Encompassing both mythological tales of the gods and heroic tales of warriors and leaders, the Norse mythological tradition offers insights into both the religious beliefs and the history of the cultures of Northern Europe between the fall of the Roman Empire and the birth of early modern national cultures. Its primary myths treat themes common to most cultures: the creation of the world, the nature of good and evil, and the cycles of life, death and regeneration. The heroic tales present glimpses of the daily life and thought, as well as of the significant historical figures and moments of the Northern tribal peoples. The Poetic Edda stands as one of the most significant literary works of the middle ages, and the Eddic tradition as a whole remains valuable not only for research into mythology and literary history, but also for the study of folklore, medieval history, and Scandinavian, Germanic, and Old English culture. Norse myths have their roots in tales told by a variety of Indo-European peoples who populated much of north and central Europe from as early as 600 B. C. These groups moved steadily south from Scandinavia, through what is now central and eastern Europe, toward the ever-expanding border of the Roman Empire. After the fall of Rome, Indo-European peoples migrated further into former Roman territory, and the Angles and Saxons settled in England. Latin culture remained dominant and the fall of the Roman Empire did not stop the spread of Christianity. By the seventh century, Christianity had spread widely throughout the British Isles and Western Europe. It would not arrive in Scandinavia for another three hundred years. It was during these years that the northernmost of the old Indo-European tribes began to move south into England and Western Europe, and as far west as Iceland and the North American continent, in the relentless Viking raids. It is these people, known as the "Northmen," who told and preserved the stories of the old gods and inspired many of the heroic legends that form the basis of Norse mythology. These stories were part of an oral tradition in a pagan culture, but the written versions that have come down to us were written centuries later, in Christianized cultures. Thus, dating the works and separating out differing cultural influences is a difficult, if not impossible, task. The primary literary sources are the Snorra Edda, the Saemander Edda, and the Skaldic poems. Saxo Grammaticus's History of the Danes, Old Icelandic sagas, primarily family histories and genealogies, and other historical accounts round out the picture. The most well known sources are the Eddas. The word Edda is of uncertain and somewhat debated origin; it is most often interpreted as a form of the plac