The 'Chinese' Theory: For and Against

[eggyk]

In Post-Post-Post-Medieval manukeyboardscripts, one often see "their" spelled as "there", "it's" spelled as "its", "you're" as "your"...  Should we see those "variants" as the (written) English language changing, or as errors made by people who are not completely fluent in it?

Are these mutually exclusive? 

What is written language evolution, if not the culmination of many common spelling errors over time? So, depending on how common each mistake is, and how negatively people react or teach against it, any one of those may one day be considered (by future historians) to be an example of english evolution.