Conversation so far:
is emmett in season 5 of switched at birth
Sean Berdy appears in season 5 of Switched at Birth as Emmett Bledsoe.
is sean berdy deaf
Sean Berdy was born deaf.
does sean berdy know american sign language
Sean Berdy's first language is American Sign Language.
how many american sign language users are there
Reliable estimates for American ASL users range from 250,000 to 500,000 persons.

Question: where did the language come from
Self-contained rewrite: where did american sign language come from