Linguistic Language Equality

All people have the ability to learn any language if exposed to it (at a young enough age). This is a biological function built into us.

This means that all brains, people and languages (including sign language) are equal.

Like the ability to walk or grow teeth, we all learn a language if exposed to it normally.

Sign Language Phonology:
direction of palm, position of hands, finger position, facial expression

The Innateness Hypothesis supports this.