One of the National Punctuation Day pages tells us the following "Punctuation Fact":
Punctuation first began to be added to texts because of declining standards of literacy. Readers had become less able to indicate their own punctuation.
English punctuation came about because people didn't know how to use punctuation?
If they mean that punctuation was standardized because of declining standards of literacy, I'm not sure how true this is. There were attempts to reform English spelling, but were there ever attempts to reform or standardize English punctuation?
There's also the implication that there is a correlation between punctuation and level of literacy. I don't know how true that is, but I do know that English writing has always had punctuation. It was sparse in Old English, but it was there. Middle English punctuation included these marks (this is from A Biography of the English Language by C.M. Millward:
By the 18th century, punctuation was much the same as it is today but it was much heavier - just look at a page of Tristram Shandy or Emma to get an idea of how heavy punctuation was then. We're actually using less punctuation now than we used to. But are we less literate?
One of the favourite things punctuation mavens like to do is complain about misused apostrophes. But in the interests of reasonableness, I'd like to point out the following bit of information, from The Oxford Companion to the English Language:
it appears from the evidence that there was never a golden age in which the rules for the use of the possessive apostrophe in English were clear-cut and known, understood, and followed by most educated people.