One of the many unwritten rules of the digital age is this: don’t write an email or a text message entirely in block capitals unless you’re shouting at the other person or sending a distress signal across. Otherwise, it’s just plain rude or a sign of digital illiteracy.
If the ancient Romans were here today to send text messages to each other and to us, they’d type everything out in caps. Not because they’re rude (some certainly were), but because lower-case characters hadn’t been invented yet. Actually, the Romans themselves had developed the ancestor of the Latin block capitals, so perhaps we’d be willing to turn a blind eye on this occasion.
The ancient world didn’t do caps locks and didn’t know the Shift key. Lower-case letterforms emerged during the early Middle Ages and swept the Western literate world. Letters and scripts had previously grown in various ways, but never before had a writing system evolved a letter case, the pairing of upper and lower case letterforms.
Developed in the 8th century and perfected in the 9th, the so-called Carolingian or Caroline minuscule was a big deal. A minuscule is not just a smaller capital letter, as the name suggests, but an astounding invention which shaped the way books were written, information was organised and knowledge was transmitted. Minuscules are faster to write, they require less pen-lift and are more susceptible to ligatures and links between them. The emergence of the minuscule in Western Latin scripts led to the division of labour of the letter case: capital letters are for certain things, lower-case letters for others. And so we get to the no-caps rule in text messages and emails.