Consider that CTE chronic traumatic encephalopathy was discovered only a couple decades ago, despite the fact it could in principle be physically observed with stone age technology [0]. Knowing and caring where to look are important, and its tricky if there's no conceptual framework for it

[0] gently bash someone on the head for decades, cut out their brain, notice it's all shrunken and weird in composition ... maybe in a culture with strong warrior and ritual cannibalism practices