Writing is far too recent for evolution to have given us a reading brain. A 2010 study comparing literate and illiterate adults showed that reading 'recycles' a visual area of the left hemisphere. In readers, it responds more to words and slightly less to faces, whose processing shifts toward the right hemisphere.
In Kuşköy, a mountain village in northern Turkey, people talk across valleys by whistling Turkish. A 2015 study showed that whistled Turkish draws on both hemispheres fairly evenly, whereas spoken Turkish relies mostly on the left. The physical form of the signal, it turns out, matters to the brain.
Speech has no gaps between words. In 1996, researchers played 8-month-old babies a continuous stream of made-up syllables for just two minutes. The infants picked out the 'words' by tracking which syllables tend to follow one another. That's probability calculation, done without a calculator or any visible effort.