Much of the pro-vegetarian research out there will try to convince you that humans are natural herbivores, that we're not meant to eat meat. In reality, our digestive characteristics show we're omnivorous, according to a talk for the Vegetarian Research Group by John McArdle. Nearly all herbivores, like cows, have fermenting vats — large chambers in their stomachs where microbes attack plant material for digestion. Humans don't.
Our jaws have both canines and molars. No, we don't have saber-teeth like many of the more famous (and terrifying) carnivores, but in the days before forks and knives, they did the job. Intestine function relies more on surface area than length. As mentioned earlier, creatures with plant-based diets need larger guts to absorb more energy, while carnivores have rather small intestines. Humans possess intermediate-sized digestive tracts.