I was just looking at some English birth records online for 1835. For the signature of the mother it had an X and said "the mark of Margaret Williams." I've found this also in probate and land records in the United States when doing research in Ohio in the 1800s. Some of my ancestors could not sign their names only an X-usually the women. They had never been to school or only home schooled by their mothers who had little or no education either.
Some how that blew my mind to consider what my life would be like IF I couldn't read or write but only sign my name with an X. Think about it for a moment. How many doors would be closed to you if you weren't literate. No schooling, a menial job, etc. This was the case also with most of the slaves in early America-they weren't literate or educated. So it's a new era we live in where few people are illiterate at least in our country. What would we do without books and the ability to write-to express ourselves with words? And how could we exist without computers?