“The development of literacy was certainly helped by the introduction of paper, which was made from rags,” says Dr Marco Mostert, a historian at the Centre for Medieval Studies, Utrecht University and one of the organisers of this year’s International Medieval Congress at the University of Leeds.
“These rags came from discarded clothes, which cost much less than the very expensive parchment which was previously used for books. In the 13th century, so it is thought, as more people moved into urban centres, the use of underwear increased — which caused an increase in the number of rags available for paper-making.”
So says a July 6, 2007 press release from the University of Leeds.
(Thanks to investigator L. Turquot for bringing this to our attention.)
UPDATE (Feb 7, 2012): That press release link has gone bad. Here’s a link to essentially the same thing.