Did you know that your teeth were designed to chew up meat?!
Did you know that your teeth were designed to chew up meat?
just a little info for all the vegetarians out there!
Answers:
To: psychoceramics@zikzak.net
Subject: psychoceramics: The Comparative Anatomy of Eating
From: Ernie Karhu
Date: Tue, 26 Mar 1996 08:38:09 -0500
Sender: owner-psychoceramics
NOTE: this author uses the term "herbivore" in the most general sense of eating only plant material, and, unfortunately, does NOT differentiate between the more-restrictive, more common, application of the word "herbivore" to refer to grazing animals only; e.g. cattle, sheep, goats, etc., which have quite special, unique adaptations necessary to eat and properly digest only grasses and leaves, and are therefore quite different in digestive physiology than the frugivorous (eats primarily fruit) apes, in which classification the human species really belongs.[LF]
The Comparative Anatomy of Eating
by Milton R. Mills, M.D.
Humans are most often described as "omnivores". This classification is based on the "observation" that humans generally eat a wide variety of plant and animal foods. However, culture, custom and training are confounding variables when looking at human dietary practices. Thus, "observation" is not the best technique to use when trying to identify the most "natural" diet for humans. While most humans are clearly "behavioral" omnivores, the question still remains as to whether humans are anatomically suited for a diet that includes animal as well as plant foods.
A better and more objective technique is to look at human anatomy and physiology. Mammals are anatomically and physiologically adapted to procure and consume particular kinds of diets. (It is common practice when examining fossils of extinct mammals to examine anatomical features to deduce the animal's probable diet.) Therefore, we can look at mammalian carnivores, herbivores (plant-eaters) and omnivores to see which anatomical and physiological features are associated with each kind of diet. Then we can look at human anatomy and physiology to see in which group we belong.
Oral Cavity
Carnivores have a wide mouth opening in relation to their head size. This confers obvious advantages in developing the forces used in seizing, killing and dismembering prey. Facial musculature is reduced since these muscles would hinder a wide gape, and play no part in the animal's preparation of food for swallowing. In all mammalian carnivores, the jaw joint is a simple hinge joint lying in the same plane as the teeth. This type of joint is extremely stable and acts as the pivot point for the "lever arms" formed by the upper and lower jaws. The primary muscle used for operating the jaw in carnivores is the temporalis muscle. This muscle is so massive in carnivores that it accounts for most of the bulk of the sides of the head (when you pet a dog, you are petting its temporalis muscles). The "angle" of the mandible (lower jaw) in carnivores is small. This is because the muscles (masseter and pterygoids) that attach there are of minor importance in these animals. The lower jaw of carnivores cannot move forward, and has very limited side-to-side motion. When the jaw of a carnivore closes, the blade-shaped cheek molars slide past each other to give a slicing motion that is very effective for shearing meat off bone.
The teeth of a carnivore are discretely spaced so as not to trap stringy debris. The incisors are short, pointed and prong-like and are used for grasping and shredding. The canines are greatly elongated and dagger-like for stabbing, tearing and killing prey. The molars (carnassials) are flattened and triangular with jagged edges such that they function like serrated-edged blades. Because of the hinge-type joint, when a carnivore closes its jaw, the cheek teeth come together in a back-to-front fashion giving a smooth cutting motion like the blades on a pair of shears.
The saliva of carnivorous animals does not contain digestive enzymes. When eating, a mammalian carnivore gorges itself rapidly and does not chew its food. Since proteolytic (protein-digesting) enzymes cannot be liberated in the mouth due to the danger of autodigestion (damaging the oral cavity), carnivores do not need to mix their food with saliva; they simply bite off huge chunks of meat and swallow them whole.
According to evolutionary theory, the anatomical features consistent with an herbivorous diet represent a more recently derived condition than that of the carnivore. Herbivorous mammals have well-developed facial musculature, fleshy lips, a relatively small opening into the oral cavity and a thickened, muscular tongue. The lips aid in the movement of food into the mouth and, along with the facial (cheek) musculature and tongue, assist in the chewing of food. In herbivores, the jaw joint has moved to position above the plane of the teeth. Although this type of joint is less stable than the hinge-type joint of the carnivore, it is much more mobile and allows the complex jaw motions needed when chewing plant foods. Additionally, this type of jaw joint allows the upper and lower cheek teeth to come together along the length of the jaw more or less at once when the mouth is closed in order to form grinding platforms. (This type of joint is so important to a plant-eating animal, that it is believed to have evolved at least 15 different times in various plant-eating mammalian species.) The angle of the mandible has expanded to provide a broad area of attachment for the well-developed masseter and pterygoid muscles (these are the major muscles of chewing in plant-eating animals). The temporalis muscle is small and of minor importance. The masseter and pterygoid muscles hold the mandible in a sling-like arrangement and swing the jaw from side-to-side. Accordingly, the lower jaw of plant-eating mammals has a pronounced sideways motion when eating. This lateral movement is necessary for the grinding motion of chewing.
The dentition of herbivores is quite varied depending on the kind of vegetation a particular species is adapted to eat. Although these animals differ in the types and numbers of teeth they posses, the various kinds of teeth when present, share common structural features. The incisors are broad, flattened and spade-like. Canines may be small as in horses, prominent as in hippos, pigs and some primates (these are thought to be used for defense) or absent altogether. The molars, in general, are squared and flattened on top to provide a grinding surface. The molars cannot vertically slide past one another in a shearing/slicing motion, but they do horizontally slide across one another to crush and grind. The surface features of the molars vary depending on the type of plant material the animal eats. The teeth of herbivorous animals are closely grouped so that the incisors form an efficient cropping/biting mechanism, and the upper and lower molars form extended platforms for crushing and grinding. The "walled-in" oral cavity has a lot of potential space that is realized during eating.
These animals carefully and methodically chew their food, pushing the food back and forth into the grinding teeth with the tongue and cheek muscles. This thorough process is necessary to mechanically disrupt plant cell walls in order to release the digestible intracellular contents and ensure thorough mixing of this material with their saliva. This is important because the saliva of plant-eating mammals often contains carbohydrate-digesting enzymes which begin breaking down food molecules while the food is still in the mouth.
Stomach and Small Intestine
Striking differences between carnivores and herbivores are seen in these organs. Carnivores have a capacious simple (single-chambered) stomach. The stomach volume of a carnivore represents 60-70% of the total capacity of the digestive system. Because meat is relatively easily digested, their small intestines (where absorption of food molecules takes place) are short -- about three to five or six times the body length. Since these animals average a kill only about once a week, a large stomach volume is advantageous because it allows the animals to quickly gorge themselves when eating, taking in as much meat as possible at one time which can then be digested later while resting. Additionally, the ability of the carnivore stomach to secrete hydrochloric acid is exceptional. Carnivores are able to keep their gastric pH down around 1-2 even with food present. This is necessary to facilitate protein breakdown and to kill the abundant dangerous bacteria often found in decaying flesh foods.
Because of the relative difficulty with which various kinds of plant foods are broken down (due to large amounts of indigestible fibers), herbivores have significantly longer and in some cases, far more elaborate guts than carnivores. Herbivorous animals that consume plants containing a high proportion of cellulose must "ferment" (digest by bacterial enzyme action) their food to obtain the nutrient value. They are classified as either "ruminants" (foregut fermenters) or hindgut fermenters. The ruminants are the plant-eating animals with the celebrated multiple-chambered stomachs. Herbivorous animals that eat a diet of relatively soft vegetation do not need a multiple-chambered stomach. They typically have a simple stomach, and a long small intestine. These animals ferment the difficult-to-digest fibrous portions of their diets in their hindguts (colons). Many of these herbivores increase the sophistication and efficiency of their GI tracts by including carbohydrate-digesting enzymes in their saliva. A multiple-stomach fermentation process in an animal which consumed a diet of soft, pulpy vegetation would be energetically wasteful. Nutrients and calories would be consumed by the fermenting bacteria and protozoa before reaching the small intestine for absorption. The small intestine of plant-eating animals tends to be very long (greater than 10 times body length) to allow adequate time and space for absorption of the nutrients.
Colon
The large intestine (colon) of carnivores is simple and very short, as its only purposes are to absorb salt and water. It is approximately the same diameter as the small intestine and, consequently, has a limited capacity to function as a reservoir. The colon is short and non-pouched. The muscle is distributed throughout the wall, giving the colon a smooth cylindrical appearance. Although a bacterial population is present in the colon of carnivores, its activities are essentially putrefactive.
In herbivorous animals, the large intestine tends to be a highly specialized organ involved in water and electrolyte absorption, vitamin production and absorption, and/or fermentation of fibrous plant materials. The colons of herbivores are usually wider than their small intestine and are relatively long. In some plant-eating mammals, the colon has a pouched appearance due to the arrangement of the muscle fibers in the intestinal wall. Additionally, in some herbivores the cecum (the first section of the colon) is quite large and serves as the primary or accessory fermentation site.
What About Omnivores?
One would expect an omnivore to show anatomical features which equip it to eat both animal and plant foods. According to evolutionary theory, carnivore gut structure is more primitive than herbivorous adaptations. Thus, an omnivore might be expected to be a carnivore which shows some gastrointestinal tract adaptations to an herbivorous diet.
This is exactly the situation we find in the Bear, Raccoon and certain members of the Canine families. (This discussion will be limited to bears because they are, in general, representative of the anatomical omnivores.) Bears are classified as carnivores but are classic anatomical omnivores. Although they eat some animal foods, bears are primarily herbivorous with 70-80% of their diet comprised of plant foods. (The one exception is the Polar bear which lives in the frozen, vegetation poor arctic and feeds primarily on seal blubber.) Bears cannot digest fibrous vegetation well, and therefore, are highly selective feeders. Their diet is dominated by primarily succulent lent herbage, tubers and berries. Many scientists believe the reason bears hibernate is because their chief food (succulent vegetation) not available in the cold northern winters. (Interestingly, Polar bears hibernate during the summer months when seals are unavailable.)
In general, bears exhibit anatomical features consistent with a carnivorous diet. The jaw joint of bears is in the same plane as the molar teeth. The temporalis muscle is massive, and the angle of the mandible is small corresponding to the limited role the pterygoid and masseter muscles play in operating the jaw. The small intestine is short ( less than five times body length) like that of the pure carnivores, and the colon is simple, smooth and short. The most prominent adaptation to an herbivorous diet in bears (and other "anatomical" omnivores) is the modification of their dentition. Bears retain the peg-like incisors, large canines and shearing premolars of a carnivore; but the molars have become squared with rounded cusps for crushing and grinding. Bears have not, however, adopted the flattened, blunt nails seen in most herbivores and retain the elongated, pointed claws of a carnivore.
An animal which captures, kills and eats prey must have the physical equipment which makes predation practical and efficient. Since bears include significant amounts of meat in their diet, they must retain the anatomical features that permit them to capture and kill prey animals. Hence, bears have a jaw structure, musculature and dentition which enable them to develop and apply the forces necessary to kill and dismember prey even though the majority of their diet is comprised of plant foods. Although an herbivore-style jaw joint (above the plane of the teeth) is a far more efficient joint for crushing and grinding vegetation and would potentially allow bears to exploit a wider range of plant foods in their diet, it is a much weaker joint than the hinge-style carnivore joint. The herbivore-style jaw joint is relatively easily dislocated and would not hold up well under the stresses of subduing struggling prey and/or crushing bones (nor would it allow the wide gape carnivores need). In the wild, an animal with a dislocated jaw would either soon starve to death or be eaten by something else and would, therefore, be selected against. A given species cannot adopt the weaker but more mobile and efficient herbivore-style joint until it has committed to an essentially plant-food diet test it risk jaw dislocation, death and ultimately, extinction.
What About Me?
The human gastrointestinal tract features the anatomical modifications consistent with an herbivorous diet. Humans have muscular lips and a small opening into the oral cavity. Many of the so-called "muscles of expression" are actually the muscles used in chewing. The muscular and agile tongue essential for eating, has adapted to use in speech and other things. The mandibular joint is flattened by a cartilaginous plate and is located well above the plane of the teeth. The temporalis muscle is reduced. The characteristic "square jaw" of adult males reflects the expanded angular process of the mandible and the enlarged masseter/pterygoid muscle group. The human mandible can move forward to engage the incisors, and side-to-side to crush and grind.
Human teeth are also similar to those found in other herbivores with the exception of the canines (the canines of some of the apes are elongated and are thought to be used for display and/or defense). Our teeth are rather large and usually abut against one another. The incisors are flat and spade-like, useful for peeling, snipping and biting relatively soft materials. The canines are neither serrated nor conical, but are flattened, blunt and small and function Like incisors. The premolars and molars are squarish, flattened and nodular, and used for crushing, grinding and pulping noncoarse foods.
Human saliva contains the carbohydrate-digesting enzyme, salivary amylase. This enzyme is responsible for the majority of starch digestion. The esophagus is narrow and suited to small, soft balls of thoroughly chewed food. Eating quickly, attempting to swallow a large amount of food or swallowing fibrous and/or poorly chewed food (meat is the most frequent culprit) often results in choking in humans.
Man's stomach is single-chambered, but only moderately acidic. (Clinically, a person presenting with a gastric pH less than 4-5 when there is food in the stomach is cause for concern.) The stomach volume represents about 21-27% of the total volume of the human GI tract. The stomach serves as a mixing and storage chamber, mixing and liquefying ingested foodstuffs and regulating their entry into the small intestine. The human small intestine is long, averaging from 10 to 11 times the body length. (Our small intestine averages 22 to 30 feet in length. Human body size is measured from the top of the head to end of the spine and averages between two to three feet in length in normal-sized individuals.)
The human colon demonstrates the pouched structure peculiar to herbivores. The distensible large intestine is larger in cross-section than the small intestine, and is relatively long. Man's colon is responsible for water and electrolyte absorption and vitamin production and absorption. There is also extensive bacterial fermentation of fibrous plant materials, with the production and absorption of significant amounts of food energy (volatile short-chain fatty acids) depending upon the fiber content of the diet. The extent to which the fermentation and absorption of metabolites takes place in the human colon has only recently begun to be investigated.
In conclusion, we see that human beings have the gastrointestinal tract structure of a "committed" herbivore. Humankind does not show the mixed structural features one expects and finds in anatomical omnivores such as bears and raccoons. Thus, from comparing the gastrointestinal tract of humans to that of carnivores, herbivores and omnivores we must conclude that humankind's GI tract is designed for a purely plant-food diet.
Summary
Facial Muscles
CARNIVORE: Reduced to allow wide mouth gape
HERBIVORE: Well-developed
OMNIVORE: Reduced
HUMAN: Well-developed
Jaw Type
CARNIVORE: Angle not expanded
HERBIVORE: Expanded angle
OMNIVORE: Angle not expanded
HUMAN: Expanded angle
Jaw Joint Location
CARNIVORE: On same plane as molar teeth
HERBIVORE: Above the plane of the molars
OMNIVORE: On same plane as molar teeth
HUMAN: Above the plane of the molars
Jaw Motion
CARNIVORE: Shearing; minimal side-to-side motion
HERBIVORE: No shear; good side-to-side, front-to-back
OMNIVORE: Shearing; minimal side-to-side
HUMAN: No shear; good side-to-side, front-to-back
Major Jaw Muscles
CARNIVORE: Temporalis
HERBIVORE: Masseter and pterygoids
OMNIVORE: Temporalis
HUMAN: Masseter and pterygoids
Mouth Opening vs. Head Size
CARNIVORE: Large HERBIVORE: Small OMNIVORE: Large HUMAN:
Small
Teeth: Incisors
CARNIVORE: Short and pointed
HERBIVORE: Broad, flattened and spade shaped
OMNIVORE: Short and pointed
HUMAN: Broad, flattened and spade shaped
Teeth: Canines
CARNIVORE: Long, sharp and curved
HERBIVORE: Dull and short or long (for defense), or none
OMNIVORE: Long, sharp and curved
HUMAN: Short and blunted
Teeth: Molars
CARNIVORE: Sharp, jagged and blade shaped
HERBIVORE: Flattened with cusps vs complex surface
OMNIVORE: Sharp blades and/or flattened
HUMAN: Flattened with nodular cusps
Chewing
CARNIVORE: None; swallows food whole
HERBIVORE: Extensive chewing necessary
OMNIVORE: Swallows food whole and/or simple crushing
HUMAN: Extensive chewing necessary
Saliva
CARNIVORE: No digestive enzymes
HERBIVORE: Carbohydrate digesting enzymes
OMNIVORE: No digestive enzymes
HUMAN: Carbohydrate digesting enzymes
Stomach Type
CARNIVORE: Simple
HERBIVORE: Simple or multiple chambers
OMNIVORE: Simple
HUMAN: Simple
Stomach Acidity
CARNIVORE: Less than or equal to pH 1 with food in stomach
HERBIVORE: pH 4 to 5 with food in stomach
OMNIVORE: Less than or equal to pH 1 with food in stomach
HUMAN: pH 4 to 5 with food in stomach
Stomach Capacity
CARNIVORE: 60% to 70% of total volume of digestive tract
HERBIVORE: Less than 30% of total volume of digestive tract
OMNIVORE: 60% to 70% of total volume of digestive tract
HUMAN: 21% to 27% of total volume of digestive tract
Length of Small Intestine
CARNIVORE: 3 to 6 times body length
HERBIVORE: 10 to more than 12 times body length
OMNIVORE: 4 to 6 times body length
HUMAN: 10 to 11 times body length
Colon
CARNIVORE: Simple, short and smooth
HERBIVORE: Long, complex; may be sacculated
OMNIVORE: Simple, short and smooth
HUMAN: Long, sacculated
Liver
CARNIVORE: Can detoxify vitamin A
HERBIVORE: Cannot detoxify vitamin A
OMNIVORE: Can detoxify vitamin A
HUMAN: Cannot detoxify vitamin A
Kidney
CARNIVORE: Extremely concentrated urine
HERBIVORE: Moderately concentrated urine
OMNIVORE: Extremely concentrated urine
HUMAN: Moderately concentrated urine
Nails
CARNIVORE: Sharp claws
HERBIVORE: Flattened nails or blunt hooves
OMNIVORE: Sharp claws
HUMAN: Flattened nails
Shut up and bring your lies elsewhere.
it doesn't matter what we're designed for, it's our choice.
You must be a genius to know that!
I've been a vegetarian for 12 years now and I thought I needed my teeth to chew my veggie food. Guess I was wrong.
And your appendix was designed to digest tree bark. What's your point?
it is my choice don't worry about my teeth
Well, okay. Fair enough. Let's all assume for one moment that our teeth ARE designed for eating meat.
Well, let's take me, a vegan. I've lived a perfectly normal life for the one year I've been a vegan. I've felt perfectly healthy, and my dentist says my teeth are in fine condition.
I used to eat meat, before I became a vegan, so I know what it's like.
Now, my teeth, which were designed for eating meat, haven't stopped me from leading a healthy, normal life without meat, and they haven't deteriorated since I became a vegan.
I personally don't see any reason to let my meat-eating teeth make me eat meat.
What a silly little (non) question!
Did you know your brain is supposed to be used to think?
yup. we're omnivores. but its our choice to not give in into out nature. as a veggie, my choice is to change what we were meant to do and protect those we call friends
our teeth are ready for chewing and they will adapt in shape, sharpness and form according to diet. if one takes liquid diet for more than 40 days the gums loosen up and teeth falls off, dare do try it and you'll be convinced all aforementioned holds true
No they are not. And get off your soapbox.
Humans are omnivores. Those teeth contain a combination of meat cutters and grain chewers. None of them are specialized to grab and hold prey.
The more important issue here is that vegetarian diet is a choice. Sometimes financial, sometimes cultural, othertimes religious, but everytime it's a personal choice. Don't go knocking other people's culture or religion. Just like it's bad form to tease someone who cannot afford a burger and have to eat leftover tubers.
Remember, it's a diet. Just see how long you last if you tease the women in Jenny Craig diet center.
Look at a dog's mouth or a cat's and tell me that your teeth look like theirs! Tell me! Do they . .. they don't because we are not designed to eat just meat!
Read VeggieRockerDude's answer.
That is if all that reading doesn't make your brain hurt. If it does, you can just go back to watching American Idol.
But I'm fine with your eating meat. As long as you have no problem watching the animal through its development and slaughter process. They don't grow cows in those styrofoam trays in the deli case, you know.
Did you know that we are also designed to be healthy and survive without it? Probably not since you seem to think you are the only one to come in here and share your news.
Last time I checked, my nails and teeth are hardly strong enough to rip apart much of anything. It sure is easy though when it's ground up and put in a nice plastic wrapping for you isnt it?
were omnivores also we dont need to grab and hold prey we have are arms and hands to do that for us
thats why were developed to eat meat and veggys, fruits ,and breads
This is just not true. Human teeth are most similar to those of a herbivore (short "fangs", multiple flat molars designed to grind rather than tear). Whoever fed you this "information"?
And your intestines are like those of a herbivore, too, that's why there are two of them (large and small). A carnivore's instestines are a single unit designed to expel their food out of their bodies in a short time. Yours are designed to digest all the fiber from a plant-based diet, more slowly.
Check your science books and see whether I'm correct or not.
Yep, as well as eat nuts, chew on fresh coconuts, bite into crispy apples, and shred a pineapple. Multi-purpose all right.
Ill put this in a simple way, may all vegetarians continue their lives as that while we carnivorous warriors help to eat them before they eat us.
Either way... less for you, more for us. THANKS!
Last time I checked its the herbivores who "chew" their food. Carnivores like to tear meat from the bones and gulp it down with little or no chewing.
Humans have spade shaped incisors that look far more like a horses or sheep's, not at all like a dog or some other carnivore. Humans also have molars in the back of our mouths made for grinding plant foods. our jaw can move from side to side and up and down. http://www.longhornm.com/images/mouth.jp... http://www.mainlinehealth.org/images/big...
A carnivore or omnivore animal have shart pointed teeth made for tearing and ripping flesh. If you look in the back of their mouths you will see only a few sharp molars. look here http://www.usmc.mil/marinelink/image1.ns... also a carnivores or omnivores jaw can only move up and down.
no, thanks for that. Never heard that from a meat-eater before...Wow what such insight you have.
Did you know you pay for slughter, torture, abuse and cruelty.
Were you designed for that ?
just a little info for all the meateaters out there !
Our teeth are designed for mashing, not so much for chewing meat. If we were natural omnivores we would have been born with much sharper teeth, not to mention the instinctual desire to go out and hunt and kill our prey, and then eat the carcass raw. That is what true meat eaters do. Our bodies are in no way designed to digest and process meat. The average colon is gunked up with years worth of partially digested meat. Disgusting but true.
Yes, that's true, and they aren't the only adaptations to us either. No sensible vegans can contest that we were deigned to eat meat. Even most vegan scientists agree that human's are designed to eat meat.
Unlike some people have said, our teeth are very well adapted to eat meat.
For instance, the post veggierockerdude made was wrong most of the way through.
The main problem is that he consistently compares us to carnivores, like dogs. We aren't carnivores, but omnivores and while we have many adaptations to eat meat we also have many to eat plants. Thus things like molars, movable lower jaw and amylase in the saliva, etc, which many people have cited as reasons we are meant to eat plants, have no bearing on whether or not we should eat meat.
Similarly with intestines. We need a long intestine (although ours is proportionally a bit smaller than a herbivores) because a long intestine is needed to digest plants. A small intestine isn't needed to digest meat but as it is easy to digest a long intestine is unnecessary. That we have a longer intestine than a carnivore also doesn't mean we aren't meat eaters.
On the other hand, look at the many differences with us and herbivores. We don't have a working intestine, or any of the measures some herbivores take to break down cellulose, like multiple stomachs or chewing cud, and nor do we have the bacteria which break it down. We can't digest cellulose because we don't have the capacity. I am yet to find a natural herbivore which cannot do this, because cellulose is so important in their diets. We don't need to however, because of meat in our diet, which is much better.
Also, that we don't have huge, viciously sharp incisors doesn't mean we aren't meant to eat meat.
When early hominids ate meat they scavenged it, as vultures do, using their fingers to get the sinews and meat other animals couldn't. It was only after that that they began to hunt the meat themselves, and only much later they began to cook it.
The last few million years of human evolution have revolved completely around tools. We used advanced stone tools long before we began to hunt our own meat, and as such there was no need for evolution to bestow us with large claws or teeth to kill prey.
It is not only carnivores who have large teeth, but also many herbivores like hippos. Their teeth are weapons and big teeth actually get in the way a bit when eating. A humans weapons are his hands and his tools, and neither do we need to rip flesh of a carcass, with our teeth.
The other problem with comparing us to mammalian carnivores is that almost all mammalian carnivores come from a single order, carnivora, thus names because it contains all the big meat eaters like cats and dogs. We are primates, and not very closely related to cats while all the members of carnivora, and thus most carnivores, are as closely related to each other as we are to monkeys.
As all primates have thumbs all carnivores have adaptations which are similar to each other because they are so closely related. To thus say that we aren't meat eaters because we don't have some of these adaptations is a fallacy.
Yes, we have many things in common with herbivores, because we eat plants. We also have as many things, if not more, in common with carnivores, as we also eat meat. Reasons we are similar to herbivores are not reasons we shouldn't eat meat as we are omnivores.
Pigs are much more similar to your average herbivore than we are, but yet it is indisputable that they are omnivores.
As for in his summary:
'Facial muscles'
We do not need a large mouth gape because we don't rip meat directly off the bone and swallow it whole. We have fingers which work just as well for these functions.
As for all the statements relating to jaws, look at a pig, an omnivore. Does it conform to all the statements there? No. Omnivores as closely related to dogs and cats as bears and badgers, also members of the carnivora order, do conform, but neither we nor pigs are as closely related as that and we are both omnivores. Also, those things aren't essential to meat eating, it just so happens that most carnivores have them though, again, due to being closely related.
'Mouth Opening vs. Head Size'
Again, we don't rip meat off the bone with out mouths (often), we don't need the large mouth that requires. Also note most carnivores kill with their mouths, which also needs a large mouth.
'Teeth'
Any meat eater will tell you our teeth are perfectly adequate at eating meat. However, most carnivores use them for other purposes too, like ripping it off the bone and even killing the prey in the first place. We don't do this and that we don't have large weapon like teeth doesn't make them any less adept at actually eating the stuff.
Looking through the other points, chewing, saliva, colon and stomach acidity can all be explained the same way. When he says omnivores he is basically talking about bears and the like, which are very closely related to dogs and cats. Looking at unrelated omnivores like pigs and you'll find big differences. Also, we use our chewing motion and saliva to deal with plant foods, this doesn't affect our meat eating capabilities.
The statement about us not being able to detoxify vitamin A, this misleading. The vast majority of vitamin A for a person on a normal diet comes from animal products, while very large doses of vitamin A can be toxic, in the amounts we generally eat it isn't at all.
'nails'
Our nails come from millions of years as tree dwellers, where they were very useful. Again, this is simply because we aren't closely related to cats and dogs (although closer than to cows and sheep) and doesn't mean we aren't meant to eat meat. Claws are weapons and many herbivores have them too, they don't directly affect diet, although of course they are often used for hunting.
As mentioned earlier, we don't need claws for hunting.
Simple research into human biology reveals how we are meant to eat meat. For one thing, our body produces hydrochloric acid and meat splitting enzymes that herbivores don't produce and are solely used for the digestion of meat. There are adaptations to our teeth (not incisors, rather the size of the jaw), stomach and intestines which have made a human being very adept at meat digestion. There is nothing wrong with the way our body digests meat, and we are so adept at eating it no scientists are of any doubt we've evolved to eat it.
In contrast, there are many reasons we aren't naturally herbivores. We cannot naturally get all the nutrients we need without animal products naturally. Vitamin B12 cannot be got, even now, without animal products or supplements, and a lack of it can cause anaemia and impending death. 60% of vegans even now have some level of B12 deficiency, as opposed to no meat eaters, which says something about how well adapted we are to a vegan diet.
All other nutrients can be got naturally. That owes to that vegetables can now be sold all year round, even out of season, and can be flown into the country from all over the world. In bygone times people could only eat the relatively small range of plants that grew in their ecosystem, and only when they were in season. Thus many more nutrients would have been unavailable and still more unavailable for most of he year. Until very recently it would have been impossible for a vegan human to live naturally without dying very quickly.
Now, meat makes up for all these lost nutrients very nicely, and it really shows how we aren't naturally vegans, as until very recently it was impossible to live like that.
@ Kelly A
Do you have a natural urge to do out and harvest some wheat? No? The fact is humans aren't rules by instinct as much as animals. On the other hand I think you'll find hunting has been seen as a very enjoyable activity throughout history to this day.
um, not really.
besides, guns are designed to shoot people, but does that make it ok to use one?
But did you know that a person can thrive on a vegetarian diet, eliminating our need for senseless killing?