This section is from the "Health and Survival in the 21st Century" book, by Ross Horne.
Towards the end of World War II when the Americans invaded the Philippines and recaptured them from the Japanese, a lone Japanese soldier ran off into the jungle there and hid, firmly believing that sooner or later the tide of battle would turn again and Japan would in the end be victorious. He therefore decided to wait things out in the jungle. He waited twenty-five years, all the while avoiding human contact, and then one day emerged from the jungle and surrendered.
Returned to Japan and medically examined, the soldier amazed everybody--he looked so young compared to other middle-aged Japanese men. His teeth were perfect and his eyesight too. He displayed none of the usual signs of degenerative disease considered normal in civilization. And yet his life had not been easy. The only possible explanation for his physical preservation was that his diet for those years had been fruit, berries and various plants eaten raw, a diet similar to that of other wild primates and that of early humans before the discovery of fire.
Life of all kinds is most prolific in tropical regions both on land and sea, and this is not to be wondered at because it is in warm and moist conditions that enzymes work most efficiently. In such a warm, moist environment it is thought that life first appeared on Earth, and it is generally accepted that it was in the tropics that the early primates evolved from lower forms of life, to be followed by the evolution of the apes and then by the first humans.
In the plant kingdom, fruit trees were late arrivals on the evolutionary scene and it is highly probable that both fruit-bearing trees and the primates evolved concurrently, which accounts for the development in the primates of stereoscopic color vision, grasping hands, specialized teeth and jaw structure, appetite for sweet-tasting food, medium-length digestive tract, and so on. In their symbiotic relationship, the fruit trees provided the primates with food and the primates unknowingly spread the fruit seeds wherever they ate or defecated, so ensuring the continued survival of the trees.
The study of comparative anatomy and the different natural diets of animals in the wild indicates strongly that the natural diet of early humans consisted predominantly of sweet fruits, and that even though millions of years have passed, the anatomy and digestive apparatus of humans has not changed and is therefore still best suited to fruit as the most suitable food. That this opinion is not just idle speculation can be quickly proven by any sick person who can break the addiction to our modern taste-stimulating foods and go on a diet of good quality fruit for just a few days. Of course the human digestive system is quite capable of handling foods of animal origin, including animal fats, but in only very limited amounts can it do so without strain, even when the foods are eaten raw as intended by Nature.
Thus it can be surmised that the ideal diet for man is one mainly of sweet fruits supplemented by various berries, green nuts, shoots and occasionally small amounts of foods of animal origin, all eaten raw. This is the sort of food eaten by man's closest relatives in Nature, the orangoutang and chimpanzee, both of which have an anatomy and digestive system almost identical to man's. Neither of these animals in the wild display tooth decay or any of the other diseases common to humans, but soon do so if kept in captivity and fed cooked and processed food.
If this surmise is correct, and if indeed humans can live in better health and for a longer time on such a natural diet, why ever did they change?
There is not a race of people anywhere today who, as a general rule, eat uncooked natural food; the majority of the world's populations base their diets on cooked grains of some kind or other, and the rest base theirs on cooked animal products supplemented by grain, dairy products and vegetables, all cooked. Fruit is looked upon more as a mere accessory to the various traditional diets rather than a sustaining food. How and why did this change come about?
Early man lived in small groups and, before the use of fire, ate his food raw like all the other creatures on Earth have done since life first began, their senses of sight, smell and taste indicating to them the foods most suitable to their systems. Population numbers were restricted by the amount of food available growing wild, but eventually with the discovery of fire it was found that various foods consumed by other animals but which were distasteful to the human palate could be made more edible by cooking, and more tasteful by artificially flavoring them with herbs and salt.
By the use of these new sources of food, greater populations could be supported, not only in areas already occupied, but in territory where food naturally suited for humans was not available.
As population pressures forced surplus people to move into less hospitable territory outside the tropics, they of necessity became reliant on a different diet, and on fire and primitive clothing for warmth. Sickness, when it occurred, was thought to be the work of evil spirits, and so witchdoctors had to be invented.