Before the making of the alphabet, did people have dyslexia? If so, what were they bad at?

What’s bothering me is that letters and the alphabet is created by humans. So what I’m trying say is that dyslexia doesn’t make any sense. Dyscalculia makes sense because math is not a creation, it’s a discovery. We did not discover letters, we created them because we learned to talk. Then someone thought it would be nice to pair a symbol with a sound to form a word later on.