What does a large neolithic settlement look like in a high-mana world? What spells are most likely to be invented first? How many people actually know one or more spells? What's obviously different? What's subtly different?

One thing I'd like to point out about THAUMATOLOGY as written: This is the academic study of magical theory and the “physics” of mana. Anyone may learn this skill, but it is easier for a mage; add Magery to IQ when learning this skill, just as for spells. The main use for this skill is magical research... Note that this implies a culture that has undertaken a study of principles and is in the process of turning those principles into a science. This does seem to be Tech level oriented in the sense of science needing literacy, for things to have occurred on a regular basis in order to study it in the first place. That it is REQUIRED for spell research introduces a paradox.

My take away from the foregoing is that it is RAW impossible, and House-Rules implausible that anyone in a neolithic setting would ever invent the first magic spell in the standard GURPS system.