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Comparison Between the Digestive Tracts of a Carnivore, a Herbivore and Man
Part 5: Conclusion
All this evidence points to our being pure carnivores, as are the big cats.
But we also have a sense of taste for sweet things, a sense we would not have if it were not useful in some way. So fruit or honey may have formed part of our diet. But it cannot have been an important part of that diet because fruit contains little or no protein, and honey none at all; and protein on a daily basis is essential for health.
The totality of evidence demonstrates that the human digestive tract is extremely inefficient when coping with foods of vegetable origin. With no bacteria and no enzymes capable of breaking down the cell walls to release the small amounts of nutrients inside, we can only eat many of these foods after they have been cooked. As Nature must have intended that all foods should be eaten raw, they cannot have formed a significant part of our diet during our evolution.
During our evolution, therefore, when we lived well, our diet must have been high in animal protein and fat, supplemented with wild fruit, but only during lean times would it include other foods of vegetable origin. As more than 99.9% of our genetic makeup evolved and was determined before we, as a species, started to heat and cook foods, that must still be the correct diet for us today.
In The Naive vegetarian I compared the size of the gorilla to that of a man. The gorilla is a herbivorous animal with a simple stomach. Robert Yerkes found that, in the wild, this vegetarian animal had many protozoa in its stomach which digested plant proteins and synthesised animal proteins. (3) In captivity, however, Yerkes noted that these protozoa gradually disappeared from the gorilla's stomach. In this state, the gorilla was unable to synthesise its own animal protein, and had to be fed meat, milk, or other animal proteins to remain healthy. This was because, although we think of the gorilla as a herbivore, it actually consumes significant amounts of 'animal' protein and fats in the form of insects and other small creatures that live on or in the leaves the gorilla eats. Like all other primates, therefore, the gorilla is not a strict herbivore.
Reference
3. The Great Apes. Yerkes R M. New Haven-Yale University Press,1929.
Last updated 4 May 2002
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