Humans communicated through images long before writing was even a thing, and some argue we are going back to that, as video story-times and long audio messages become more popular and words are no longer obligatory for communication outside face-to-face encounters.
Of course, simpler examples of memes also existed in ancient times, and they were probably caricatures drawn on the spot that took no longer than 5 minutes to make. I know paintings aren't exactly memes, but it's funny to think of them that way.
What is a meme in the end, if not a visual representation of something usually (not always) funny? Memes can also be disturbing or enigmatic, and some of us react to that with laughter; ancient paintings can work like that as well.
We see them all with a solemn aura they didn't necessarily have at the time. Maybe some of them were painted to express something funny, and the artists knew people at the time would have the tools to interpret them. It's just that today we don't, and we think of them as something very serious.
I'm not saying all of them were made with comedic intent, but I'm sure some of them were. I like to think I can tell by the expressions on some of the characters, but maybe it's just my imagination.
Could you imagine if humans in the future thought of our memes as something really serious? That would be the ultimate joke.
In the meantime, here are some classical art memes to snobishly laugh at.