Laura Spinney in The Guardian:
When the great library at Alexandria went up in flames, it is said that the books took six months to burn. We can’t know if this is true. Exactly how the library met its end, and whether it even existed, have been subjects of speculation for more than 2,000 years. For two millennia, we’ve been haunted by the idea that what has been passed down to us might not be representative of the vast corpus of literature and knowledge that humans have created. It’s a fear that has only been confirmed by new methods for estimating the extent of the losses.
The latest attempt was led by scholars Mike Kestemont and Folgert Karsdorp. The Ptolemies who created the library at Alexandria had a suitably pharaonic vision: to bring every book that had ever been written under one roof. Kestemont and Karsdorp had a more modest goal – to estimate the survival rate of manuscripts created in different parts of Europe during the middle ages.
Using a statistical method borrowed from ecology, called “unseen species” modelling, they extrapolated from what has survived to gauge how much hasn’t – working backwards from the distribution of manuscripts we have today in order to estimate what must have existed in the past. The numbers they published in Science magazine earlier this year don’t make for happy reading, but they corroborate figures arrived at by other methods. The researchers concluded that a humbling 90% of medieval manuscripts preserving chivalric and heroic narratives – those relating to King Arthur, for example, or Sigurd (also known as Siegfried) – have gone.