One of the comments I get frequently is that “humans are meat-eaters by nature, or else we wouldn’t have the sharp teeth we have for tearing flesh.” This particular argument’s always been flawed because our “sharp” teeth are really far from a true carnivore or omnivore’s equivalent. Nonetheless, for all I know, we could be “meant” to eat meat by our design, but none of the arguments I’ve heard have really swayed me. Not that it ever mattered to me anyway, and not that it would change my mind about how I, personally, want to eat.
Herbivore, Omnivore, or Carnivore? by Milton R. Mills, M.D. outlines the traits of typical plant-eaters, meat-eaters, and ominivores versus our own. His findings are interesting and summarized well at the end of the article. I’m not qualified to verify or debunk any of his logic, but it’s worth taking a look at.