This is an argument that goes back and forth; all kinds of answerer's are given on both sides of the debate. There is a way to find out and that is to examine the evolutionary anatomy of the human body to see how its digestive track has evolved. This is short compilation of physiology findings concerning carnivores and herbivores. I used the charts provided on http://wiki.answers.com/Q/Are_humans_omnivores_or_herbivores
Here is an answer to the question as to whether or not humans are herbivores or carnivores. Milton R. Mills MD. is the author of "The Comparative anatomy of eating" I suggest that you visit the link to see his chart,
Comparative physiology shows how the human body has evolved. The idea that primitive man ate a diet of primarily of meat appears to be flawed. At best early man was an omnivore with the greatest part of his diet being plant based like we see in gorillas, orangutans and chimpanzees.
Let’s look at comparative anatomy of herbivores and carnivores. There are many similarities, but there are very distinct differences. First off herbivores have no claws; Carnivores have claws, and long sharp teeth on the end of a long snout for ripping and tearing hide and flesh. Herbivores molars are not pointed but flat for grinding. Herbivores jaws have the ability to move sideways to aid in there mastication. Carnivores and omnivores have very little sideways jaw movement and swallow their food whole. Herbivores have pores in their skin to perspire through; Carnivores perspire through the tongue to cool down their bodies. Carnivores have evolved very acid saliva with no enzymes for digestion. Herbivores have alkaline saliva with ptyalin enzymes to help digest fruits and grains. Carnivores have very strong hydrochloric stomach acid to help digest flesh. Herbivores have evolved stomach acid twenty times weaker than carnivores. Carnivores have evolved a relative short digestive track to pass the material through quickly so as to not absorb too many fats. Herbivores have evolved very long digestive tracks in order to aid in extracting nutrition from plants.
Now let’s look at human anatomy and see how the human has evolved. Humans have no claws, their teeth are flat and their jaws move sideways for grinding and chewing their food before swallowing. Humans have pores in their skin that they perspire through to cool themselves. Humans have evolved hydrochloric stomach acid twenty times weaker than carnivores. Humans have alkaline saliva with ptyalin enzymes for digesting fruits and grains. Humans have evolved a very long digestive tract like other herbivores.
When you examine how the human anatomy has evolved it appears obvious that we are herbivores. There is a lot of evidence but one of the most notable is that humans will generally become ill or dye when eating uncooked flesh like a wild carnivore. Humans do not contain the stomach enzymes that kill harmful bacteria and parasites that carnivores do. Also all carnivores produce enzymes that neutralize the uric acid in their diet, humans produce no such enzymes. When a human eats a diet high in animal products they suffer a number of heath problem associated with uric acid. Gout, kidney stones, kidney failure, arthritis, certain cancers, cardio vascular disease and now uric acid has been connected to chronic brain ischemia.
Humans do not digest animal proteins well, and animal based foods cause many detrimental health problems for humans. Second because humans are anatomical herbivores we thrive on plant proteins. Comparative anatomy shows herbivore physiologic evolution in humans. Dennis Renner