Todesking wrote:
I think high fevers can cause infants to go deaf or mute. They really did not have antibiotics back in the ancient times so maybe infections or fevers went unchallenged did major damage to the young.
As a matter of fact it's antibiotics (mainly aminoglycosides) that did and still cause a lot of damage to hearing in children.
But seriously, as ruveyn said above, in quite a number of cases muteness is due to deafness, not to a speech disorder.
It is true that some deaf people can speak but they can't learn on their own if the deafness is prelingual (that is, if the age of onset was before spoken language developed), they need to be taught specifically how to talk without hearing.