For millennia people with hearing impairments encountered marginalization because it was believed that language could only be learned by hearing the spoken word. Ancient Greek philosopher Aristotle, for example, asserted that “Men that are deaf are in all cases also dumb.” Under Roman law people who were born deaf were denied the right to sign a will as they were “presumed to understand nothing; because it is not possible that they have been able to learn to read or write.”
Pushback against this prejudice began in the Renaissance. The first person credited with the creation of a formal sign language for the hearing impaired was Pedro Ponce de León, a 16th-century Spanish Benedictine monk. His idea to use sign language was not a completely new idea. Native Americans used hand gestures to communicate with other tribes and to facilitate trade with Europeans. Benedictine monks had used them to convey messages during their daily periods of silence. (See also: New device translates brain activity into speech. Here's how.)
Inspired by the latter practice, Ponce de León adapted the gestures used in his monastery to create a method for teaching the deaf to communicate, paving the way for systems now used all over the world.