Modern man is accustomed to a constant regular intake of food - external nutrition. But nutrition can also be internal, it happens during fasting.
Even primitive man was familiar with hunger. His well-fed days were replaced by starvation, which is why our ancestors, whenever possible, tried to eat more than the body needs, that is, they gorged on a "rainy" day. Thus, primitive man created reserves of glycogen and fat, which helped him to survive in difficult times.
