Yep, this is why I said "one single thread," because I was hesitating to post this, because there are tons of other threads, like all of the beards that exist for *other* reasons. Greek philosophers and those who followed in their tradition were so big on beards that forcing them to shave was a means of humiliation, and you get philosophers saying they would commit suicide rather than lose their beard! (I forget if anyone actually did--Selena may remember what the source for this is, I'm going from memory.)

By the way, one thing I also meant to add is that in the later empire period, you also start to get the emperors depicted bigger than surrounding figures, as realism becomes less important than "obey us."

(I haven't even talked about Hellenistic trends, but because of the rise of monarchs ruling pieces of Alexander's empire, you get some of the same tendencies, as well as other interesting innovations.)