In order to read, one needs to write, which was only invented (letters, alphabets, symbols, etc) 6,000-5,000 years ago. This is considered too recent in human evolution to develop a gene for reading.

“The herculean job of educators is no less than to help the brain develop a skill it could not otherwise, which requires creating an entirely new circuit in the brain.” — The Reading League

Then how have we learned to read? Mostly by practice and constant repetition, such as in school, that changes your brain (which is called neuroplasticity).

This makes your brain adapt to letters by using functions meant for recognizing faces, seeing shapes, and hearing sounds (hence why some hear words in their brain as they read).

And yes, writers take this further.

P.S. This post is oversimplified.