At the time of Mohammed. . .?

Back then, 99.99% of people were illiterate. Only the wealthy and educated could read. Mohammed was also illiterate. Even 60 years ago, most people in Saudi Arabia were illiterate. Only after the discovery of oil, the oil based economy made it possible to have publicly funded education systems. It is very common in Saudi Arabia that teenagers are able to read, but their parents are completely illiterate.