Here's a breakdown:
* Natural Development: Sign languages developed organically, much like spoken languages. Deaf individuals, finding spoken language inaccessible, created their own ways to communicate visually.
* Diverse Origins: Different sign languages evolved independently in different regions and cultures. There are hundreds of distinct sign languages, each with its own grammar, vocabulary, and history.
* Influence of Oralism: In the 18th and 19th centuries, the "oralist" movement aimed to teach deaf people to speak and lip-read. This approach discouraged sign language use, but ultimately failed to replace it completely.
* Modern Recognition: In the 20th and 21st centuries, sign languages have gained greater recognition as legitimate languages, leading to their incorporation into education systems and cultural acceptance.
So, while no one "invented" sign language, it's a testament to the ingenuity and adaptability of the deaf community. It's a rich, complex, and fascinating language with a long and ongoing story.