How much medieval literature was lost to time?

Hi there, it’s Rose! I write for Datawrapper’s blog, and my subjects today are fish and chivalry.

When you first encounter a new environment, it seems to be full of new things. So many different birds in this field! So many different fish in this lake! And as time goes on and you explore more deeply, you’ll keep finding more that you didn’t notice at first — but the rate of discovery will tend to slow down. It might take a long, long time before you’ve really observed everything there is to see.

That’s a problem for science, because it means that research expeditions have a kind of diminishing returns. We can’t keep sitting in the field for years in the hopes of sighting just one more new bird — eventually we’ll have to go home, knowing that our observations are still a bit incomplete. Ecologists model this incompleteness with a kind of chart known as a species discovery curve:

Every new individual animal sighted could be a member of a new-to-us species — but the likelihood of that happening gets lower and lower as our list of already-sighted species gets longer and longer. As the curve flattens out, it gives a decent estimate of the real number of species present, including the ones we never saw for ourselves.

Ecologists may have been the first to model it, but this dynamic pops up in all kinds of situations, any time we’re trying to account for the full contents of a large, diverse environment. In fact, the data I used to create the curve above isn’t about birds or fish at all. What are we spotting here? Medieval manuscripts, of course:

In this paper (Kestemont et al. 2022), the lake is the whole body of medieval literature as it was actually written, and the fish we get to observe are those manuscripts that survive in today’s libraries and archives. Those surviving manuscripts represent a good variety of “species” — distinct works of literature, many of which exist in more than one copy — but of course there must originally have been even more. Creating this species discovery curves allowed the researchers to estimate that the whole medieval lake once contained about 371 additional works beyond those we know today. Wouldn’t it be exciting if one of them swam to light?

That’s it for today! Come back next Thursday for a Weekly Chart from our visualization developer Elliot.