A raw, vegan diet is the natural diet for humans. Note that, despite the above, there are sufficient, powerful, spiritual and ethical reasons to be a vegetarian. Within a given species, diets can and will vary per habitat and territory. If a food is not present in the habitat or territory, the animal cannot eat it. Witness the wide variation in diet among hunter- gatherer societies, and across nations and cultures.
Intelligent adaptation is the key to survival of our species.
It should be noted that it is due to our omnivorous adaptation skills that we survived as a species, and we are alive now, so we can debate the fine points of diet. Simple logic suggests one should eat foods that are agreeable to you, in the form that is easiest to digest. Diet is not so trivial that it can be reduced to inaccurate, simplistic slogans. There's a lesson here, if you are open to receive it. Wild animals die of disease, despite eating a raw, natural diet.