Do we think even those dots date back to the original, or did they evolve later
For contrast, here's a page from Philodemus' On Choices and Avoidances from P.Herc. 1251. dating to between 50 to 1 BCE.
At that time, everyone just "knew" where to read punctuation and the script was written continuously and in all "capitals" to our way of thinking... But that was just how they wrote. Once Greek started to be a lingua franca among disparate cultures (or just to make it easier to read!), the punctuation and accent marks were "invented" and added to the text.
It's the difference between this:
ITWOULDBEQUITEDIFFIC
ULTBUTNOTIMPOSSIBLE
TOREADTHISWAYINTEXT
and this
It would be quite difficult, but not impossible, to read this way in text.
So, the "punctuation marks" were always there, after a fashion, even if they weren't written. That said, it can be interesting to see how phrases were punctuated. Here's an example from my characteristics of the sage: