Literacy isn't genetic.

Yeah, what OZ said! Literacy is not a heritable trait. And anyways, many medieval clergymen were the lesser sons of wealthy individuals; as these monks had older brothers who were busy passing on the family legacy, they weren't "completely" removing their genes from the gene-pool, and if they were at least bright enough to learn how to read and write, then odds are good that their money-and-sex-having older brothers were bright enough, too. In fact, it could even be argued that sticking less-important members of your family in a monastery *improves* the viability of your family's genetic material, on the grounds that every non-cloistered member of a family is a potential competitor over inheritance, and thus, a potential source of murder and instability.

There's also the question of fitness - i.e. what does it mean when we say that a certain trait improves an organism's reproductive fitness? Modern people tend to believe in the progressive narrative of Evolution: "lower" forms give way to "higher", and species "evolve" into even more perfect beings, as defined by the traits contemporary society judges to be valuable (increased intelligence, for example). This is not, however, actually the case. Reproductive fitness is just that, *reproductive* fitness - what makes you better at having sex and ensuring your children have sex, too! Darwinian natural selection is blind and stupid, and while situations we might interpret as "progress" can and do arise by accident, you're just as likely to see less-intelligent segments of the population outbreeding the more-intelligent, IF conditions are such that lower intelligence is selected for, or even simply ignored (e.g. the medieval social order, under which people did not think in Darwinian/ eugenical terms, and physical health was more valuable to survival than idle brain power). Was monastic celibacy dysgenic? No, but even if it were, I don't think it it would matter; "dysgenic", in the context of selecting for potential literacy, amounts to nothing more than a social value judgement, and as such is no less valid than any rival "eugenic" strategy.

I'm inclined to agree with all that, and add that I bet those monks were doing a lot more breeding on the side than went on the record.