Animal Rights and Vegan Advocacy
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Anatomy Objections Section

Reasoned responses, organized as talking points, to common objections, concerns, and questions regarding animal rights and veganism.

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“Eating animals is natural—it’s part of the circle of life and we are apex predators on top of the food chain.”“eating animals is natural—it’s part of the circle of life and we are apex predators on top of the food chain.”“eating animals is natural—it’s part of the circle of life and we are apex predators on top of the food chain.”[toc label="talking points"]in objecting to veganism and animal rights, some invoke a series of statements centering around the idea that eating animals and their secretions is natural. these statements often include a reference to the circle of life, apex predation, and the idea that humans are on top of the food chain—all in an attempt to prove that the eating of animal flesh, chickens' eggs, and cow's milk by humans is as natural as the laws of physics.here we show that these declarations are not germane to the case for veganism. but even if they were, they are still defeated by taking a closer look at the assertions, which we do.

assertions as to what is natural are not pertinent to the validity of veganism.

simply put, the case for veganism is that it’s wrong to cause unnecessary harm to animals. eating products made from animals harms animals, and because we don't need animal products to be healthy, the harm is unnecessary. the issues of harm and necessity are covered in our article "an introduction to veganism."so even if the practice of eating animals were natural, even if it were somehow part of some nebulous circle of life, and even if we were apex predators on top of the food chain—all that would still not justify causing unnecessary harm to others.

naturalness says nothing about rightness.

the occurrence of a behavior in the natural world says nothing about the morality of the behavior. rape, defined as forced sexual intercourse, is not unusual in other species. amphibians, reptiles, birds, fish, and mammals engage in the practice.((palmer, craig t. “rape in nonhuman animal species: definitions, evidence, and implications.” journal of sex research26, no. 3 (august 1989): 355–74. https://doi.org/10.1080/00224498909551520 )) infanticide is committed by dolphins, lions, and baboons.((thompson, helen. “why some mammals kill babies of their own kind.” smithsonian, november 13, 2014. https://www.smithsonianmag.com/science-nature/why-some-mammals-kill-babies-own-kind-180953318/ )) we would not say these behaviors are moral, but we could not deny that they are natural in the sense that they occur in nature.

our natural abilities suggest we are not natural predators, much less apex predators.

we may be apex predators in the sense that we are not eaten by other species, but this is a consequence of our not living in a more natural environment, such as the wilderness, as well as our ability to use our mental faculties to avoid being eaten. it is not because of physical strength or agility, as is the case with other apex predators, such as the african wild dog, the lion, or the tiger.natural predators have physical characteristics that allow them to seize and kill their prey, rip and tear their prey's flesh, and then eat the raw flesh. humans are not so good at this. although we have developed tools that overcome our physical limitations, we don't have what it takes to do this unaided. also, we insist on cooking the flesh we eat, which no other species of flesh eater does.

our physiology and anatomy suggest that flesh is not a natural food for humans.

a comparative review of the physiology and anatomy of animals reveals that humans match closely with herbivores, not omnivores or carnivores. we cover this topic in more depth in our post in response to the assertion that "humans are natural omnivores—we digest meat, have canine teeth, and have front-facing eyes."as that post demonstrates, the length of our intestines, the structure of our teeth, nails, jaw, mouth opening, and facial muscles, our digestive enzymes, our stomach acidity, our ability to detoxify vitamin a, and our urine concentration all point toward humans being herbivorous.((mills, milton r. “the comparative anatomy of eating.” vegsource interactive inc 26 (1996). https://www.scribd.com/doc/94656/the-comparative-anatomy-of-eating ))

there is nothing natural about how we get our meat, dairy, and eggs.

selective breeding has resulted in farmed animals that produce far more flesh, far more eggs, and far more milk than their forebears would produce in a natural environment.dairy cows produce more than three times the amount of milk they did several decades ago, which burdens them and results in their development of unnaturally large udders.((blayney, don p. the changing landscape of us milk production. us department of agriculture, economic research service, 2002. https://www.ers.usda.gov/webdocs/publications/47162/17864_sb978_1_.pdf?v=41056 ))an egg-laying hen produces more than 300 eggs per year, but the jungle fowl from which they were bred lay four to six eggs in a year.((cheng, h.-w. “breeding of tomorrow’s chickens to improve well-being.” poultry science 89, no. 4 (april 1, 2010): 805–13. https://doi.org/10.3382/ps.2009-00361 )) also, laying hens are bred to lay large eggs, which they are not evolved for; this stresses their reproductive system and causes such problems as osteoporosis, bone breakage, and uterus prolapse.((jamieson, alastair. “large eggs cause pain and stress to hens, shoppers are told,” march 11, 2009, sec. finance. https://www.telegraph.co.uk/finance/newsbysector/retailandconsumer/4971966/large-eggs-cause-pain-and-stress-to-hens-shoppers-are-told.html ))the modern broiler chicken is unnaturally large and has been bred to grow at an unnaturally fast rate and have large breasts. this selective breeding causes numerous afflictions: leg disorders; skeletal, developmental, and degenerative diseases; heart and lung problems; breathing difficulty; and premature death.((stevenson, peter. “leg and heart problems in broiler chickens.” compassion in world farming, january 2003. https://www.ciwf.org.uk/media/3818898/leg-and-heart-problems-in-broilers-for-judicial-review.pdf ))farmed animals are far from natural—they could not survive in a natural environment. in our contrived animal agriculture system, the concepts of "natural," "circle of life," "apex predation," and "food chain" simply don't apply.

we shouldn't base our morality on animal behavior.

we humans have moral agency, meaning we can judge the consequences of our actions. this implies a degree of responsibility, or duty, to do what is right. nonhuman animals seem to lack the ability to fully contemplate the moral consequences of their actions.((regan, tom. the case for animal rights. university of california press, 2004. 152-154 ))but even if they could, that does not mean we should model our morality on the behaviors of other species. instead, we should use our moral agency to make ethical decisions, not invoke nebulous and impertinent concepts of what is natural to justify behaviors that unnecessarily harm others.
“Farming animals gives them their lives, protects them, and gives their lives meaning.” To Do“farming animals gives them their lives, protects them, and gives their lives meaning.” to do“farming animals gives them their lives, protects them, and gives their lives meaning.” to do
“Our brains evolved from eating animals.” To Do“our brains evolved from eating animals.” to do“our brains evolved from eating animals.” to do
“Humans are natural omnivores—we digest meat, have canine teeth, and have front-facing eyes.”“humans are natural omnivores—we digest meat, have canine teeth, and have front-facing eyes.”“humans are natural omnivores—we digest meat, have canine teeth, and have front-facing eyes.”[toc label="talking points"]those objecting to veganism often bring up one or more in a series of related complaints: that a vegan diet is not natural, that humans are omnivores and can digest meat, or that canine teeth and front-facing eyes are indications we are predators and not prey.these protests are adequately dismissed with the first point below, which explains why they are not pertinent to the validity of veganism and therefore cannot diminish the case for veganism.although no further exploration of these claims is necessary once their lack of pertinence is demonstrated, we expound on these claims in case you're interested. it turns out that even if the objections were pertinent, they'd be nevertheless weak.

the case for veganism does not depend on humans being natural herbivores or having specific physical traits.

vegan diets are beyond sufficient for human health. even if humans were natural omnivores and our teeth and eye locations supported that assertion, the science is clear that a strictly herbivorous vegan diet is not only adequate but also beneficial to our health.this is confirmed by harvard medical school, mayo clinic, cleveland clinic, kaiser permanente, newyork-presbyterian, the academy of nutrition and dietetics operating in the united states, the dietitians of canada, the british dietetic association, the dietitians association of australia, and others.((see http://justiceforanimals.org/objections/quote-we-need-animal-products-to-be-healthy/ for statements and citations ))these prominent organizations and others could only have made statements declaring the adequacy and salubriousness of a vegan diet if science supported such statements. cleveland clinic even explicitly states, "there really are no disadvantages to a herbivorous diet!"((“understanding vegetarianism & heart health.” cleveland clinic, december 2013. https://my.clevelandclinic.org/health/articles/understanding-vegetarianism-heart-health ))the case for veganism has nothing to do with this issue. simply put, the case for veganism is that it's ethically wrong to cause unnecessary harm to animals. because it's not necessary to eat animal products for nutrition, any claims that we are natural herbivores are rendered meaningless.

the evidence is strong that we lean toward being herbivorous.

the fact that humans are behavioral omnivores and are able to get nutrition from both plants and animals says nothing about what is natural or optimum.our anatomy and physiology suggest that we are more herbivorous than omnivorous. a number of notable people have observed that anatomical and physiological traits of humans closely match herbivores'.dr. mills's the comparative anatomy of eating((mills, milton r. “the comparative anatomy of eating.” vegsource interactive inc 26 (1996). https://www.scribd.com/doc/94656/the-comparative-anatomy-of-eating )) shows we more closely match herbivores in eighteen traits, as summarized below.
  • intestines
    • small intestine
      • carnivore: 3–6 times body length
      • omnivore: 4–6 times body length
      • herbivore: 10–12+ times body length
      • human: 10–11 times body length
    • colon
      • carnivore: simple, short, and smooth
      • omnivore: simple, short, and smooth
      • herbivore: long, complex; may be sacculated
      • human: long, sacculated
  • teeth
    • incisors
      • carnivore: short and pointed
      • omnivore: short and pointed
      • herbivore: broad, flat, and spade shaped
      • human: broad, flat, and spade shaped
    • canines
      • carnivore: long, sharp, and curved
      • omnivore: long, sharp, and curved
      • herbivore: dull and short or long (for defense) or none
      • human: short and blunted
    • molars
      • carnivore: sharp, jagged, and blade shaped
      • omnivore: sharp blades or flattened
      • herbivore: flat with cusps vs. complex surface
      • human: flat with nodular cusps
  • saliva
    • carnivore: no digestive enzymes
    • omnivore: no digestive enzymes
    • herbivore: carbohydrate-digesting enzymes
    • human: carbohydrate-digesting enzymes
  • stomach
    • stomach type
      • carnivore: simple
      • omnivore: simple
      • herbivore: simple or with multiple chambers
      • human: simple
    • stomach acidity with food in stomach
      • carnivore: ≤ ph 1
      • omnivore: ≤ ph 1
      • herbivore: ph 4–5
      • human: ph 4–5
  • chewing
    • carnivore: none; swallows food whole
    • omnivore: swallows food whole or simple crushing
    • herbivore: extensive chewing necessary
    • human: extensive chewing necessary
  • nails
    • carnivore: sharp claws
    • omnivore: sharp claws
    • herbivore: flat nails or blunt hooves
    • human: flat nails
  • jaw
    • type
      • carnivore: angle not expanded
      • omnivore: angle not expanded
      • herbivore: expanded angle
      • human: expanded angle
    • joint location
      • carnivore: on the same plane as molar teeth
      • omnivore: on the same plane as molar teeth
      • herbivore: above the plane of the molars
      • human: above the plane of the molars
    • motion
      • carnivore: shearing; minimal side-to-side motion
      • omnivore: shearing; minimal side-to-side motion
      • herbivore: no shearing; good side-to-side, front-to-back motion
      • human: no shearing; good side-to-side, front-to-back motion
    • major muscles
      • carnivore: temporalis
      • omnivore: temporalis
      • herbivore: masseter and pterygoids
      • human: masseter and pterygoids
  • mouth opening vs. head size
    • carnivore: large
    • omnivore: large
    • herbivore: small
    • human: small
  • facial muscles
    • carnivore: reduced to allow wide mouth gape
    • omnivore: reduced
    • herbivore: well developed
    • human: well developed
  • liver
    • carnivore: can detoxify vitamin a
    • omnivore: can detoxify vitamin a
    • herbivore: cannot detoxify vitamin a
    • human: cannot detoxify vitamin a
  • kidney
    • carnivore: extremely concentrated urine
    • omnivore: extremely concentrated urine
    • herbivore: moderately concentrated urine
    • human: moderately concentrated urine
percy bysshe shelley was a poet, not a scientist, but it's interesting to note that he wrote an entire book, a vindication of natural diet, published in 1884, that drew on comparative anatomy to argue that humans were best suited to a vegetable diet.((shelley, percy bysshe. a vindication of natural diet. percy bysshe shelley. kindle e-book, a public domain book. vegetarian society, 1883. http://amzn.com/b0076qxqji )) this predates dr. milton mills's work, discussed above, by over 100 years.evolution and anthropology may support the contention that we are more herbivorous. biologist rob dunn declares in scientific american that "human ancestors were nearly all vegetarians." in making that assertion, and in questioning the validity of paleo claims, he deems it important to look at the diets of our ancestors at the time our guts were evolving. he states that for primates, a group to which humans belong, plants "were our paleo diet for most of the last thirty million years during which our bodies, and our guts in particular, were evolving. in other words, there is very little evidence that our guts are terribly special and the job of a generalist primate gut is primarily to eat pieces of plants."((dunn, rob. “human ancestors were nearly all vegetarians.” scientific american blog network, july 22, 2012. https://blogs.scientificamerican.com/guest-blog/human-ancestors-were-nearly-all-vegetarians/ ))dr. colin barras, a paleontologist and science writer, believes that "archaeologists tend to emphasise the role of meat in ancient human diets, largely because the butchered bones of wild animals are so likely to be preserved at dig sites. edible plants may have been overlooked simply because their remains don’t survive so well."((barras, colin. “ancient leftovers show the real paleo diet was a veggie feast | new scientist.” new scientist, december 5, 2016. https://www.newscientist.com/article/2115127-ancient-leftovers-show-the-real-paleo-diet-was-a-veggie-feast/ ))our inability to kill and eat animals and process meat without sophisticated tools is telling. omnivores and carnivores who eat animals have the athletic prowess and anatomical features necessary to not only catch and kill their prey but also to tear and rip apart the carcass and process it for eating.humans lack these features and must use sophisticated tools, such as spears and knives, to accomplish these tasks.the adverse effects of eating animal products suggest that we are more herbivorous. supporting the contention that our evolution and physiology are herbivorous is the overwhelming scientific evidence that eating animal products contributes to all manner of health problems, including increased risk for obesity, high blood pressure, diabetes, heart disease, and cancer.((m.d, michael greger, and gene stone. how not to die: discover the foods scientifically proven to prevent and reverse disease. 1 edition. new york: flatiron books, 2015 )) ((“the china study: the most comprehensive study of nutrition ever conducted and the startling implications for diet, weight loss and long-term health: thomas m. campbell ii and t. colin campbell: 8580001064130: amazon.com: books.” accessed january 12, 2018. https://www.amazon.com/china-study-comprehensive-nutrition-implications/dp/b006dukw0e/ref=tmm_hrd_swatch_0?_encoding=utf8&qid=1515791692&sr=1-1 )) ((davis, brenda, and melina vesanto. becoming vegan: the complete reference to plant-based nutrition (comprehensive edition). accessed january 12, 2018. https://www.amazon.com/becoming-vegan-reference-plant-based-comprehensive/dp/1570672970/ref=tmm_pap_swatch_0?_encoding=utf8&qid=1515791822&sr=1-1 )) ((“plantbasedresearch | an online library of research relevant to plant-based nutrition.” accessed january 12, 2018. http://plantbasedresearch.org/ ))

the notion of a natural diet is problematic.

the concept of a natural diet might make some sense in the context of gatherers and hunters. but since the invention of agriculture, with its selective breeding of both plant and animal species, the label loses its meaning.also, to make the claim that humans are natural omnivores, one needs to define what is meant by "natural" in this context. if by "natural" you are referring to the ability to obtain nutrients, then humans are omnivores, as we can digest both plants and meat. but, as shown earlier, that still cannot negate the case for veganism.if you mean it's natural because it's nutritionally the best diet for humans, then you are on shaky ground. there's an increasingly large body of research, as mentioned and cited above, supporting the contention that the closer we are to a varied herbivorous diet, the greater our general health and the lower our risk for a multitude of chronic diseases.finally, the claim that humans are natural omnivores can be thought of as an example of the naturalistic fallacy. that is to say, being natural doesn't make something ethically or nutritionally sound.

canine teeth are not indicators of dietary requirements.

as elaborated on earlier, the argument for veganism does not depend on humans having any specific physical traits. but the part of the objection that pertains to canine teeth is discussed here only because it is frequently voiced.hippopotamuses, gorillas, camels, and saber-toothed deer all have sizable canines, and all are herbivorous. herbivores use canine teeth in various ways. sizable canines in herbivores are often for defense. the relatively short, blunted canines in humans can assist in biting into hard, crunchy plants (such as apples) and ripping vegetable matter, preparing the food for grinding by the other teeth. one thing seems obvious—human canines are not adequate to kill prey or tear raw flesh for eating.

front-facing eyes are not necessarily indicative of predator status.

the claim is made that since many prey animals have eyes on the side of the head and many predator animals have eyes on the front of the head, it follows that humans, who have eyes on the front of the head, are designed to eat copious amounts of meat.the point is made moot, however, not only by the fact that the argument for veganism does not depend on physical traits but also by the fact that our closest relatives in the animal kingdom, the primates, have eyes in the front of the head.at least three advantages of frontal eyes for primates have been proposed.binocular vision is crucial for the manipulation of plant foods. a study titled "binocularity and brain evolution in primates," published by the national academy of sciences, concludes that "fine-grained stereopsis [binocular vision] is likely to be critical for the visually guided, delicate manipulation of plant foods."((barton, r. a. “binocularity and brain evolution in primates.” proceedings of the national academy of sciences of the united states of america 101, no. 27 (july 6, 2004): 10113–15. https://doi.org/10.1073/pnas.0401955101 ))the ability to "see through" foliage is advantageous. theoretical neurobiologist mark changizi proposes in the journal of theoretical biology the "x-ray vision" hypothesis. according to changizi, front-facing eyes gave our ancestors the advantage of being able to "see through" the cluttered foliage in the forest. you can see this effect, he states, by placing a finger in front of your eyes and noting that the finger does not block the view of anything behind it.((changizi, mark a., and shinsuke shimojo. “‘x-ray vision’ and the evolution of forward-facing eyes.” journal of theoretical biology 254, no. 4 (october 21, 2008): 756–67. https://doi.org/10.1016/j.jtbi.2008.07.011 ))arboreal locomotion requires accurate depth and distance perception. the depth and distance perception afforded by front-facing eyes was useful to our ancestors in jumping from branch to branch and tree to tree. this idea was proposed in 1922 by edward collins and has subsequently been expanded and refined.((goldman, jason g. “evolution: why do your eyes face forwards?” bbc, october 28, 2014. http://www.bbc.com/future/story/20141013-why-do-your-eyes-face-forwards ))
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