Impossible to truly know. Writing may well have started with doodles, notes, even jokes on materials like leaves or wood that didn’t survive.

What survives are the "important" texts because you would deliberately put them on durable material. That creates a bias where early writing looks purely transactional.

Same reason we think of pyramids when we think of ancient architecture: stone lasts, wood doesn’t.

That's true we don't know anything about markings that were made on organic materials.

We do know that art and other markings date tens of thousands of years before the first proto-writing. Writing is specifically about markings that form a language. So doodles and visual jokes (e.g. phalluses) wouldn't count. I don't know what you mean by notes, but writing notes without a language would be difficult I suspect.

But there could early languages that were written on organic materials. The main problem is there's a bootstrapping problem where you need to account for how the first one developed at all. After that you can continuously improve over time.