How did people know what was safe to eat in pre historic times? Was it just passed down knowledge or was taste all you needed to be able to tell? Hypothetically speaking, would a caveman get sick if he ate yogurt that fermented too much while straining? What if it is sour and a bit bitter, instead of only a bit sour?
What if the taste was very tolerable, and the caveman could even see himself spreading it on bread or toast?
Would the caveman get sick if he ate it with a bit of honey? What if the initial milk was left fermenting at about 30C for 8h, acquiring the consistency and taste of yogurt, and left to strain for 24h, also at 30C?