I think before modernization, we probably only ate every so often. Not daily like we do now. Hunters would only be able to bring in food every once in a while etc. Meanwhile while fats and meats weren't available we'd eat very low fat foods.
This would cause the bile to build up, and when the hunters would bring home a large fatty meal, our bodies are tuned to the smell fat and we would eat that.
Just saying this because I have fasted for 2-3 days then eaten a very fatty meal and gotten stones out.