Reading and hand signals

The opening paragraph of an article on hand motions and representing arithmetic reasoning

The value of handwaving to arithmetic | A handwaving approach to arithmetic | The Economist

HUMAN language is the subject of endless scientific investigation, but the gestures that accompany speech are a surprisingly neglected area. It is sometimes jokingly said that the way to render an Italian speechless is to tie his wrists together, but almost everyone moves their hands in meaningful ways when they talk...

Is an excuse for me to again reference an old idea that doesn't seem to have caught on.

Almost thirty years ago, puzzling about why humans are able to translate written squiggles into concepts and thoughts, I wondered about evolutionary antecedents. I concluded that we humans are able to interpret letter and word forms because we already had the brain mechanisms to read hand shapes, and that we probably had those mechanisms before we could speak.

So it's not surprising that deaf persons can read; reading may be older than speaking.