Cats are carnivores. Humans are not.
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A Question of Design

                                                          Carnivore


'Animals who eat meat and those who eat plants face very different issues when dinner time arrives. Plants, because they are sedentary, encase their tissues in tough fibrous coverings for support and protection, and thus require a large amount of digestive processing to extract nutritional value from them. By contrast, “meat” (in the form of live animals) usually does not want to be eaten and is, therefore, recalcitrant, combative and uncooperative – it tends to run away.

Accordingly, plant eaters (herbivores) are optimized for foraging, batch feeding and prolonged digestion, whereas meat eaters (carnivores/omnivores) are designed for predation and the consumption of huge, infrequent meals.

Meat eaters are all equipped for short bursts of extreme speed that allows them to ambush and/or run down prey. Their limbs have been lightened to allow for fast running and their paws have been modified into compact clubs armed with claws.

When tackling struggling prey, the most vulnerable parts of their anatomy – the abdomen and gonads – are shielded behind the muscular armored chest. Their incisors have been reduced to short pointed pegs, while their canines are huge sharp elongated daggers used for ripping and killing. Their jaw joint is on the same plane as their cheek teeth, and there is no horizontal side-to-side motion of the lower jaw.
This makes their jaws very stable and allows them to operate like a pair of shears. Their molars are sharp, jagged and blade-shaped. The upper molars vertically slide past the lower molars in a slicing motion when the jaw is closed. These animals do not chew their food. Instead, they slice off huge chunks of meat and swallow them whole. They do not have digestive enzymes in their saliva since flesh-digesting enzymes released in the unprotected mouth would quickly destroy the oral cavity.

Their strongly acidic stomachs are huge storage vats that account for 60-70% of the total capacity of their GI tracts. Meat has no fiber and is, therefore, easily digested. Thus, their small intestines are very short (only 3-6 times their body length) and are optimized for protein and fat absorption. Their large intestines are short straight and smooth and designed for evacuation purposes only.

What about “By-design” Omnivores?

                                                     Omnivore


The one design concession “by-design” omnivores such as bears and raccoons have made to plant eating is that one or more pairs of their molars have modified from sharp blades to flattened grinding surfaces.
This allows them to crush and swallow a limited amount and range of plant foods such as fruits, berries, roots and tubers. However, they otherwise retain the typical carnivore tooth design and jaw mechanics, and their short small intestines do not allow them to adequately handle large amounts of plant fiber. Hence, a true natural omnivore is a carnivore that has been minimally modified to eat a limited range of soft, pulpy plant foods, but is still equipped to run down, kill, dismember and consume prey.

I Herd That!

                                                   Herbivore


Large mammalian herbivores tend to be social animals living in large herds/communities/cities. Because they must cover significant distances looking for and gathering plant foods, their limbs are modified for prolonged energy-efficient standing and walking. Instead of claws, their nails are blunt and used for digging and peeling. They have muscular lips, a small mouth opening and well-developed cheek muscles.
This creates a “walled-in” oral cavity that facilitates the crushing and grinding action of chewing. The jaw joint is above the plane of the cheek teeth and the lower is “L-shaped” causing the upper molars to come to rest on top of the lower molars when the jaw is closed. This allows the jaw to function like a nut cracker rather than a pair of shears.

The upper molars cannot vertically slide past the lower molars. But because the lower jaw has a pronounced horizontal side-to-side motion, the upper and lower molars horizontally slide across one another creating the grinding action of chewing. Accordingly, the molars are not sharp and blade-shaped, but are squared, flat-topped and abut one another forming extended grinding surfaces. The incisors are broad, flattened and spade-shaped and used for cropping and peeling. The canines may be absent, as in cows and sheep; shortened and reduced, as in horses and humans; or dagger-like and used for defense, as in hippos and some primates. Herbivores also usually have carbohydrate digesting enzymes in their saliva that begins the process of digestion while food is still in the mouth. In fact, the purpose of chewing (including chewing the cud) is to mix food with digestive enzymes to facilitate the process of digestion.
Plant tissues contain large amounts of fibrous material. The end result is that plant foods require extensive processing to extract their nutritional content. Because of this, herbivores consume smaller, more frequent meals, and tend to have much longer and, in some cases, much more elaborate digestive tracts than their meat-eating counterparts.

In a typical herbivore, the stomach holds less than 30% of the total capacity of the GI tract. On the other hand, the small intestine is extremely long and is usually more than 10-12 times the body length and has an unlimited capacity for carbohydrate absorption. The large intestine or colon is also relatively long and complex and frequently has a pouched appearance.

Here’s Looking at You

                                                         Human


In every respect, humans show the anatomic and physiologic features typical of an herbivore. A full and complete discussion of these features is well beyond the scope of this short article. What follows is a random sampling of facts.

Upright posture leaves the human abdomen, ovaries and testes completely exposed and, potentially, fatally vulnerable. Whereas standing and walking are very energy-efficient for humans, running is not.

We are extremely slow runners and have very poor stamina. We have a carbohydrate-digesting enzyme in our saliva called salivary amylase.

The human esophagus does not handle poorly chewed food very well. Over 90% of the people who choke to death each year choke on meat.

Human body length (head to tail bone) is typically 2.5 to 3 feet. Thus, at >25-30 feet in length, the human small intestine is clearly designed for digesting plant material.

Only herbivores have an appendix. No matter how much fat and cholesterol you feed carnivores like dogs and cats, they NEVER develop coronary artery disease.

In places where people eat a high fiber, whole food diet, appendicitis and diverticulosis are unknown.
Studies in western countries have shown that on average, vegetarians have smarter children, suffer significantly lower rates of chronic disease, obesity and dementia, and live longer than their meat-eating counterparts.