Slow growth of literacy

Thought this was an interesting map from the Wikipedia page on literacy

“The slow spread of literacy in the ancient world. The dark blue areas were literate at around 2300 BCE. The dark green areas were literate at around 1300 BCE. The light green areas were literate at around 300 BCE. Note that other Asian societies were literate at these times, but they are not included on this map. Note also that even in the colored regions, functional literacy was usually restricted to a handful of ruling elite.”