Paul Neilson Very good question.

A mixture of soot, gum arabic, and vinegar. In Roman times lead-based ink was used (as the Herculaneum scrolls have shown recently).

They used a insect gall from oak or other trees, it was more of a black colored acid and it burned into the skin of the parchment

Papyrus paper was used very early in Egyptian antiquity. 🪔~~📜~~🪔 Ashes and oil are enough for training so find a culture without writing ✍ then perhaps ink would be unknown. Paleolithic cave painting use a form of painting so technically it could be said ink predates cuneiform and hieroglyphics. Unless the argument that in antiquity stone carving is preferred but that is counter-intuitive parents didn't want children running... 🏃‍♂️ around with chisels and carving tools .🔧 🔨 Of course earlier on it was discovered Mud can be formed into tablets and baked on the sun. Certainly some body's forefather tried to make a honey-do🍯 list during a mighty rain storm,🌧 thus discovering baked tablets last longer and by accident invented brick making by default. Before that people played in the ashes of camp fire 🔥 and therefore ink was discovered.