When our ape ancestors began walking upright 5 million years ago, their diet was certainly all raw: tender, juicy meat worms, crispy and delicious beetles, a handful of strawberries here, a fruit picked there, and sometimes, the scraps left by other carnivores. One thing is certain: our ancestors, for the energy needed to survive, had to put everything edible into their stomachs. At that time, finding food was the entire day's work.
Around 1.5 million years ago, humans learned to use fire. With the use of fire and tools, everything began to become simpler: people started to be able to hunt more prey and could divide it into smaller pieces. Fire helped people make tuber plants and other hard-to-digest plant foods, which were previously inedible, acceptable to the human digestive system. At this evolutionary stage (the era of Homo sapiens), the human brain volume was also expanding rapidly. The reason for this is still just speculation. But one thing is certain: it is closely related to the human nutritional structure. The brain is the organ in the human body that requires the most energy. It is widely believed that meat and easily available carbohydrates, such as the starch in tubers, met the growing energy demands of the brain.
In the process of finding and digesting food, apes spent most of their days. When the proportion of plant-based food in an animal's diet is larger, the animal's intestines will be longer, thus requiring more energy to digest food. Because plants contain resistant substances, they are more difficult to digest compared to meat. Carnivores have shorter intestines. In the course of evolution, the human digestive system evolved into an omnivorous organ form, from the jaw to the teeth to the intestines. The length of the human intestine is between that of herbivores and carnivores. The intestine of a chimpanzee (which mainly eats plant-based foods) is nearly twice as long as that of a human.
This evolution happened because a part of the human digestive work was transferred from the inside of the body to the outside—through roasting and cooking over an open flame. The energy saved in this way could then be supplied to the brain. This promoted more creativity in our ancestors' thinking and further improved the body's ability to digest and absorb plant foods, continuing to reduce the burden on the intestines. Frying, stir-frying, grinding, roasting, fermenting, brewing—all these skills made it easier for modern humans (whom anthropologists call Homo sapiens) to digest and absorb food. Therefore, the advent of cooking was also a decisive step in human evolution, especially as it gave humans more time and energy for other work.
Despite these improvements, our ancestors' work was still quite arduous. It is hard to imagine that this gradual and laborious food processing method did not bring them benefits. If "naturalist food" (referring to a raw food diet) had so many advantages, we would surely see the benefits that this effortless food processing brought to those "people living in nature" (referring to indigenous peoples living in a primitive state). But the opposite is true: the sophistication of these people's food processing is about the same as ours. Although there is certainly a loss of nutrients during food processing, it is a good compromise compared to the toxins or substances that hinder digestion in the food itself.
Whoever today advocates abandoning the wok wants to return to the Stone Age. This person would probably have to sacrifice his brain for a longer intestine!