Certainly. But what I was commenting on was the claim that, because "there are basically no migration stories in _any_ indo-european mythological cycles or oral traditions," we can conclude, "migration or invasion (...) was a gradual process that wouldn't have been particularly noticeable in any one life time." I don't think that conclusion is justified.

There's one good reason to believe that they wrote it down (mostly) unaltered and continued transmitting it (mostly) unaltered, which is that they continued copying it and reciting it well past the point where they even understood what many of the words meant any more, and they developed a lot of techniques to recite it and memorize it based purely on phonemes and developed ideas about how the sounds themselves carried religious power, divorced of any meaning. That's not to say that they didn't understand it at all, but surely if it were going to be altered, they would have updated the language to something more understandable at some point. Instead they wrote commentaries about the text, reinterpreting it over time.

It wasn't really until the 19th century that it was re-translated and the connection to other indo-european cultures and pantheons was rediscovered.

> Were there such events? [That is, events in early 10th century France that eventually led to English becoming a sort of pidgin French, full of words like "eventually" and "sort" that didn't exist in Beowulf]

There certainly were; quoting https://en.wikipedia.org/wiki/Richard_I_of_Normandy (28 August 0932 – 20 November 0996):

> Richard either introduced feudalism into Normandy or he greatly expanded it. By the end of his reign, the most important Norman landholders held their lands in feudal tenure.

Normandy, as you may or may not know, is in France.

Then, a century later, his great-grandson, Duke of Normandy, conquered England, subjugating the Britons, Anglo-Saxons, et al., under a French-speaking noble elite. If Jarl Rikard had been cut down by bandits in his youth, or had merely failed to enlist the Norman landholders' swords under his banner (and that of his son, grandson, and great-grandson), the Norman invasion would not have happened. Similarly, if Richard's son Richard had been unable to escape from the court of King Louis IV in 0946, or unable to then win back Normandy from the king by force of arms, his grandson William would have been in no position to conquer—and it is unlikely that the subdivided Duchy would have been able to raise an army to successfully invade England, a feat that has not been repeated in the ensuing 959 years. And so on.

> Of course it’s debatable but there is some evidence that oral knowledge can be preserved for thousands of years.

Yes, your comment was written in reply to a comment naming one of the most surprising examples of such preservation, as a result of non-literate societies, as you said, "put[ting] put in massively more effort into preserving oral traditions". Nevertheless, they seem to preserve massively less historical knowledge despite that effort.