The Human Herbivore

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Humans are often viewed as omnivorous organisms at the top of the food chain.  However, when viewed closely, one must begin to question why that is.  The comparative anatomy of humans seems to suggest that, perhaps, we were designed to be herbivores.  From our dentition to our stomach acidity, all roads point to a vegetarian diet.  However, typical humans eat a wide variety of animal matter.  Is this due to our design or are we meat-eaters because it is available and we were raised on it?  I would like to propose that humans are anatomically herbivorous and opportunistic carnivores.
Herbivores are organisms that feed mainly on plants.  Elephants, rabbits, and sheep are common herbivores.  Herbivores have an extensive digestive system to digest the complex foods that they eat.  It takes a lot to digest plant material, so the herbivores intestines are long to accommodate.  Herbivores have dull, flat teeth for grinding their food.
Carnivores are organisms that feed mainly on other animals.  Lions, dogs, and snakes are common carnivores.  Carnivores have a small digestive tract filled with acid to quickly digest the animal’s flesh before it begins to rot in the intestines.  Carnivores, generally, have sharp teeth and claws to catch their prey and tear its flesh.
While humans can tolerate a variety of different diets, it is a wonder to see that some choose to avoid animal products.  In the United States, about 2.8% of the population claims to be vegetarian.  Humans are the only organisms in which vegetarianism and non-vegetarianism exist.  Some people decide to become vegetarian due to religious conviction, nutritional or medical affects, ethical dilemmas, or psychological discomfort.  When the benefits in health of being a vegetarian are addressed, one begins to wonder why that is not our choice as a species.  Were we made to be herbivores?
Many factors seem to prove as positive evidence to proving that humans were, in fact, designed to be herbivores.  According to Bernard Campbell (1985), our teeth are much more similar to herbivores than to carnivores or omnivores.  Our canines are not sharp, so they cannot tear away flesh, and our back molars are flat and good for grinding vegetables and fruits.  Our fingernails are much more similar to those of herbivores rather than the sharp claws of carnivores and omnivores.  Also, we cannot detoxify vitamin A in our liver, we have moderately concentrated urine, we perspire through the pores in our skin, our colon is long, and our stomach takes up less than a third of our digestive tract.  All of these attributes in our anatomy are similar in herbivores and different in carnivores and omnivores.
Humans, as well as herbivores, possess salivary amylase, an enzyme used to break down carbohydrates in the mouth.  This enzyme is not present in carnivores or omnivores.  Human and herbivore stomach acidity is much more alkalinic in comparison with carnivores (Herrera and Pellmyr 2002).  This is because we do not need the acidic juices to break down as much meat.  Carnivores and omnivores tear away the flesh and blood of their prey and swallow it whole.  The meat is digested mainly by the stomach acid and is passed quickly through the system due to the short intestines.  Human and herbivores have to chew their food, break it down slowly in our long intestines to absorb all nutrients.  The raw meat that carnivores eat would be hard for humans to digest.  We tend to cook our meat, denaturing the proteins, making it easier to chew and also to get rid of the bacteria that could cause illness.  Also, herbivores have a large cecum and an appendix, which is not as large in carnivores.  Our vestigial appendix may show that our ancestors were herbivorous.
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The fossil record of our ancestors seems to prove that we were originally herbivorous.  A. africanus and A. robustus were both herbivores.  A. afarensis is thought to have become bipedal in order to reach fruit from the trees.  This may lead to the conclusion that they were also herbivorous.  However, when we get to Homo habilis, we begin to see adding meat into the diet.  It is believed that Homo habilis scavenged dead animals.  As our ancestors began to live in adverse climactic conditions, we see that they hunted because vegetation was scarce (Harris and Ross 1987).  Also, with the use of tools and control of fire, our ancestors began to cook the meat so they could eat it.  We are the only animal to cook our meat before we eat it.  If a deer is burned in a forest fire, a carnivorous animal will not eat it.  Since our ancestors ate meat when vegetation was scarce and fire was available, it seems viable to claim that humans are opportunistic carnivores.  Even in today’s society, we eat meat because it is readily bought at the grocery store and refrigerated to keep it fresh.  However, the opportunistic feeder theory can not be scientifically proven, because we know that traits can not be acquired.  Therefore, we can claim that we are omnivores by behavior and not be evolution.  We eat meat because we can, but not because we were meant to.
Some humans have eaten meat for so long that they have developed a genetic predisposition to not being vegetarian.  The Tibetans, in the upper Himalayas, are an ethnicity that has subsisted on meat for thousands of years.  They can’t grow much outside of barley.  They use barley to make tsampa, which is dough made with barley flour.  Other than that, they consume many products from the yak.  They use yak milk, yak butter, yak cheese, and the meat of the yak.  Their offspring cannot survive without meat because they have lived with it for so long.  Even the Dalai Lama couldn’t survive without meat.  He tried to give it up once, but became very ill.
Some of our closest relatives are herbivorous.  Gorillas are herbivorous ground feeders.  And our two closest believed relatives eat mainly fruits and vegetables.  The bonobos are mostly frugavorous, while about 5% of the chimpanzee’s diet is composed of meat.  The meat they normally consume is termites, birds, monkeys, and pigs.  Female chimpanzees actually eat about two times as much meat as the males.
Vegetarianism can be very beneficial to a human’s health.  It decreases the chance of colon cancer, which is caused by the putrefication of meat in the colon.  Eating excess meat increases cholesterol.  A high cholesterol diet has no negative effect on a carnivore, however, in a human, high cholesterol can lead to heart disease.  Being a vegetarian can decrease the rate of osteoporosis, which is due to calcium deficiency.  Also, it decreases the chance of kidney damage due to nephritis, which occurs when the uric acid produced during protein digestion attacks the kidneys.  There are many diseases that we can get from eating a carnivorous diet that we are not supposed to.  Natural carnivores do not suffer from heart disease, cancer, diabetes, strokes, or obesity because their bodies are equipped to deal with the saturated fats and cholesterol in meat.  Also, scientists have proven that animal protein can be harmful to our health.  We take in two times more protein than we need on a daily basis.  The protein from plants alone would be sufficient to obtain the amino acids we need to create proteins.
In conclusion, all anatomical and physiological evidence points to herbivorous origin in humans.  Our digestive system was designed to break down plant matter.  It is much harder for us to digest meats than any other source of energy.  The fact that we have to cook our meat in order to digest and receive the proper nutrients from it shows that we were not made to eat meat.  Without cooking the meat or having the proper tools to kill and tear apart the flesh of the animal, we would not be able to eat the meat we do.  It is only because we have a society and culture full of tools that we can even digest the meat.  And at that, the meat that we eat, which contains saturated fats and cholesterol, can lead to heart disease and other illnesses.  Therefore, with the evidence presented relating to comparative anatomy, humans were designed to be herbivores and choose to be omnivores based on opportunity.

Literature Cited
Campbell, Bernard. Human Evolution. 4th. Hawthorne, NY: Aldine De Gruyter, 1985. Print.
Herrera, Carlos, and Olle Pellmyr. Plant-Animal Interactions. Oxford, UK: Blackwell Science Ltd, 2002. Print.
Harris, Marvin, and Eric Ross. Food and Evolution. Philadelphia, PA: Temple University Press, 1987. Print.

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