Uh...actually our teeth etc are designed around grinding plants...not ripping meat.
You're actually incredibly wrong Bill, and I'd tell you why, but I'm drunk right now. Just know that you're wrong for now.
Good news everybody!: I sobered up and can't sleep. And here's why nobody should care about the "design" of our teeth:
Humans and chimps split from the same ancestral tree 2.5 million years ago, and spurred on the path to a belly 40% smaller than the mostly vegetarian chimpanzee, and a brain 3 times larger. Thus, even though early hominids had teeth very similar to the modern gorilla, modern humans have changed drastically.
Stomach size is markedly different between us and other great apes- humans' stomach small intestine, and colon are 10-24%, 56-67%, and 17-23% of total gut volume in humans, while for orangs and chimps it is 17-20%, 23-28%, 52-54% in orangs and chimps, respectively. In other words, they have massive colons to support fermentation of vegetation, whereas we have comparatively large stomachs, to digest more meat.
The human small intestine, at 23 feet, is a little under eight times body length (assuming a mouth-to-anus "body length" of three feet). This is about midway between cats (three times body length), dogs (3-1/2 times), and other well-known meat eaters on the one hand and plant eaters such as cattle (20 to 1) and horses (12 to 1) on the other. This tends to support the idea that we are omnivores. Herbivores also have a variety of specialized digestive organs capable of breaking down cellulose, the main component of plant tissue. Humans find cellulose totally indigestible, and even plant eaters have to take their time with it. If you were a ruminant (cud eater), for instance, you might have a stomach with four compartments, enabling you to cough up last night's alfalfa and chew on it all over again. Or you might have an enlarged cecum, a sac attached to the intestines, where rabbits and such store food until their intestinal bacteria have time to do their stuff. Digestion in such cases takes place by a process of fermentation--bacteria actually "eat" the cellulose and the host animal consumes what results, namely bacteria dung.
The most recent ancestors to homo sapiens sapiens (modern humans) are homo neanderthalensis (Neanderthals) and homo sapiens (Cro-Magnon Man). The two hominids had extremely similar diets, and both were about as close to pure carnivores as any primate has ever been.
Neanderthals unequivocally ate a diet that consisted of virtually nothing but meat- 10000-12000 calories of it a day. They also lacked sharp teeth and claws, but guess what? They didn't need them, because THEY HAD STONE TOOLS. In fact, hominids have been using tools for over 2 million years- plenty of time for them to develop the requisite biology for the digestion of meat. Neanderthals had even bigger brains than modern humans, which is important due to the fact that their diet was so heavily meat-based, and the metabolic requirements of larger brains would necessitate calorically-dense food consumption, which means they had to eat meat, or they'd die. This is why gorillas are lazy mother****ers, and exhibit very little social interaction, whereas humans have stuff like Facebook. The adoption of carnivory by Oldowan hominins can be linked directly to the evolution of the hominin brain and social systems and the very fact that this was facilitated by the use of stone tools distinguishes us from non-human primates, as their lack of tool use limits the usefulness of their predation.
At one point in history, the Earth's total population of humans dropped to between 5,000 and 10,000 individuals, due to the eruption of Mt. Toba in Sumatra, which killed off most of the available plant and animal life on Earth in 71,000 BC. During this period of time, humans were confined to an extraordinarily small area of Africa that escaped glaciation, where they subsisted on a diet that was approximately 50-70% meat and 50-30% plants, respectively. This diet was necessitated by the die-off of plants and animals, and the lack of a varied diet that could have been otherwise obtained though plant gathering. It was at this time that the Neanderthal diet came to consist of naught but meat, due to the complete lack of availability of edible vegetation, which likely lasted for at least 1000 years.
