Are humans omnivores or herbivores?

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Most humans are behavioral omnivores, but are we naturally so? Are we fit for eating meat and cheese as much as fruits and vegetables? Or are humans natural herbivores?

Humans are omnivores[edit | edit source]

Omnivores are animals anatomically and physiologically adapted to eating both plant and animal matter.

  • Argument for Argument for Humans gain significant nutrition and energy from meat.
    • Objection Objection Animal products contain components which cause many prevalent chronic diseases, amongst which cholesterol, which causes the inflammation of the arteries and can lead to atherosclerosis,[1] cardiovascular disease and strokes; saturated fat; animal protein; heme iron in red meat, which the human body lacks the capacity to regulate and is associated with a higher risk of colorectal cancer.[2][3]
  • Argument for Argument for Humans have a trophic level of 2.21 (same as anchovy and pigs).[4]Anchovy subsist primarily on zooplankton.[5]Pigs are omnivores. Animals with such a trophic level can subsist on a widely varied diet.
    • Objection Objection Level 2 of the trophic level index includes herbivores, level 3 or higher includes carnivores. A trophic level of 2.21 doesn't imply that humans are omnivores.
  • Argument for Argument for Our closest evolutionary relatives, chimpanzees and bonobos, are omnivores.[6][7] As their biology most closely resembles ours, it's more likely that humans are omnivores too.
    • Objection Objection A study from Scientific America states that chimps eat meat on average 9 days a year and bonobos even less.[citation needed] They eat according to their surroundings, if there is no meat they won't eat meat and therefore live herbivorously. Which would lead me to conclude that if we don't need to eat meat, we can be herbivores.
      • Objection Objection The article you mention (which is neither a study nor a review, it's a thought piece) classifies meat as mammalian flesh when referencing the "9 days a year" data point you chose. In the same article it points out how chimps regularly eat termites and ants, which are still meat and eaten much more frequently.
      • Objection Objection Animals cannot eat something that they can't get. A chimpanzee is an omnivore, just because it can survive on plants does not make it a herbivore. Using that logic, the Inuit people are carnivores, because plants are largely unavailable in their lands.
        • Objection Objection Carnivores have also been reported eating plants.[8][9] They are carnivores nonetheless.
  • Argument for Argument for Humans wean earlier than herbivores, a pattern that matches that of carnivores.[10] Chimpanzees (our closest evolutionary cousin) wean their young on average at around 5 years old and orangutans (the apes closest to our body weight) wean on average at 7.7 years old, which almost no human society does. Meanwhile, the average human weaning age is 2 to 4 years old,[11] which is considerably shorter than in chimpanzees and orangutans, even accounting for cultural differences and individual preferences.
    • Objection Objection Many herbivores wean earlier than humans, such as cattle and sheep.
  • Argument for Argument for Humans are able to digest meat and absorb its nutrients, which we would be unable to do if we were herbivores.
    • Objection Objection the capacity that humans have to eat meat does not imply that meat is healthy. It only means it is a reliant source of energy. Many other foods, however, are also energising, but unhealthy. Many other herbivores have been seen eating meat, which makes them opportunistic feeders [12] and not necessarily omnivores.
      • Objection Objection This is not the point of the debate. Anyone can argue that anything has a risk. The point that we are able to use meat's nutrients stands.
  • Argument for Argument for Humans, like many predators, have forward-facing eyes rather than eyes on the side of our head as prey would. This would imply that we were designed to hunt and eat other species.
    • Objection Objection Many predators don't have forward-facing eyes, and many herbivores have forward-facing eyes.
    • Objection Objection Humans descend from tree-dwelling animals, that needed precise forward-looking binocular vision to avoid falling when leaping and moving around.
  • Argument for Argument for The vast majority of humans practice an omnivorous diet and have been doing so for millions of years, and many live a long, healthy life.
    • Objection Objection This does not describe the physiology of humans but only their will. This logic would mean that if humans all decide to eat exclusively meat this makes them carnivores, and if they all decide to eat exclusively vegetables they are now herbivores.
      • Objection Objection For the most part, "omnivore", "carnivore" and "herbivore" have historically been defined by behavioral measures. Numerous species that have previously been defined as herbivores, including hippopotamus,[13][14] white tailed deer,[15] giraffe warthog and waterbuck,[16] sheep,[17][18] cattle,[19][20] rabbits,[21] duikers,[22] bonobos,[23] chipmunks,[24] squirrels,[24]and others, have been shown through behavioral observation, or through fecal and stomach content analysis (both the result of behavior) to deliberately consume meat and carrion, even predating on bird eggs, nestlings, insects, frogs, turtles, lizards and other small animals. These findings cause scientists to rethink the categorization from herbivore to omnivore, or at the very least "Partially omnivorous". If other animal species are defined by their behavioral diet, than so must humans.
        • Objection Objection That would defeat the purpose of this series of these arguments and objections, as it would beg the question: can we really be defined as herbivores/omnivores/omnivores? People have eating what they want for a long time and a plant-based diets / regular omnivorous diets / inuits have demonstrated that it is possible to survive a lifetime under all diets.
    • Objection Objection If humans were meant to eat meat, why would nature dictate that we have to cook or cure to make it safe for consumption?
      • Objection Objection Humans can, and do, consume raw meat. However, cooking has an evolutionary advantage in that it increases food efficiency. It makes the nutrients inside the food more accessible, which allowed the ancestor species of H. sapiens that discovered cooking to spend less time foraging, chewing, and digesting. Thus, humans developed a smaller, more efficient digestive tract, which combined with the more nutritionally accessible food and consequent energy surplus, enabled larger brain growth. While humans can still digest raw meat, our digestive tracts evolved in response to the discovery of cooking and are now adapted to digesting cooked food.
  • Argument for Argument for Omnivorous behavior in humans is a cultural universal (with few exceptions like Jains, Amish and Hindus). There is considerable evidence that such cultural universals can be attributed to our genetics, and in turn to our physiology.[citation needed]
    • Objection Objection It's more the reverse that environment shape genetics: "biology" or "nature" (first opposed to supernatural not cultural/social) as a social construct, epigenetics, nurture or purely cultural/social overdeterminations, etc.[clarification needed]

Humans are herbivores[edit | edit source]

Herbivores are animals anatomically and physiologically adapted to eating plant material as the main component of their diet.

Arguments for[edit | edit source]

  • Argument for Argument for Humans have a trophic level of 2.21 (same as anchovy) and that is an average (some humans have a higher trophic level, like inuits, which means that the majority of humans are indeed plant-based) and like many other studies similarly shows, we were even more plant-based before the industrial revolution.[4]
    • Objection Objection Anchovy subsist primarily on zooplankton.[5] Pigs are omnivores. This suggests that humans are omnivores rather than herbivores.
  • Argument for Argument for Some of our closest evolutionary cousins (chimpanzees, bonobos, gorillas) are herbivores.
    • Objection Objection Chimps and bonobos frequently eat termites, ants and other insects, which are still meat.
    • Objection Objection Chimps have been documented hunting and eating small mammals.[25]
      • Objection Objection This doesn't make them omnivores, but opportunistic feeders.[12]
  • Argument for Argument for Humans lack claws, sharp teeth or other natural weapons.
    • Objection Objection The invention of tools for hunting and killing prey meant there was no longer a need for costly evolutions such as claws and sharp teeth that didn't fit a purpose. No longer requiring claws because easier to craft tools fit the purpose also contributes to increased manual dexterity, which was a key component in human evolution.
    • Objection Objection Our natural weapon is our brain, which can and is used to make other weapons and strategies.
      • Objection Objection Our brain which shows compassion and empathy towards other animals, also great sorrow when they die is an argument for humans being herbivores. Our brain has provided us with the knowledge about nutrition to maintain a long and healthy life without eating meat or dairy. So we therefore do not have the natural weapons anatomically to be carnivorous or omnivorous, our "natural weapon" the brain has worked against the omnivorous argument.
        • Objection Objection Compassion and empathy are subjective and have not been shown to stop humans from "wanting" to eat meat. In fact, by 2022 the meat industry is projected to have grown by double what it was in 2016.[26]
  • Argument for Argument for An average human adult has a 22 feet long intestinal tract, small and long combined. The chest size of an adult is about 26 inches. The ratio is therefore 10.15. Herbivores are known to have an intestinal tract of 10 to 12 times their chest length.
    • Objection Objection Human gut length is much shorter than in other species because of the evolution of cooking. As cooking made food more nutritionally accessible, there was no longer need for evolutionary expensive excess gut tissue.

Arguments against[edit | edit source]

  • Argument against Argument against Humans can't derive energy from cellulose due to a reduced cecum and colon. All other herbivores and plant-based omnivores (e.g. great apes, pigs) can do this [citation needed].
    • Objection Objection Dietary fibers (which include insoluble fibers like "cellulose") count as 2kcal in average and these undigested carbs seems more like a necessity for us and other herbivores in regards to many aspects of health (typical western diet is even deficient in fibers). Herbivores do not create any enzyme that breaks down cellulose. Instead, they eat food that contains these enzymes.
  • Argument against Argument against Humans require vitamin B12 in their diet, unlike herbivores which can make their own in their colon with the help of bacteria.
    • Objection Objection Humans also create vitamin B12 in their colon with the help of bacteria. However, no animal can assimilate their own B12, they must get it from outside of their body. Most animals lick bacteria-rich soils. Humans can cultivate their own vegetables without any chemicals and make sure they grow in rich soil. If they don't wash the vegetables with chlorinated water, B12 will be found on it.
      • Objection Objection Humans cannot get the recommended amounts of vitamin B12 without meat in their diets. Herbivorous animals have both different gut flora, which allow for the production of vitamin B12 and have fore gut fermentation, meaning they can absorb it. Human gut fermentation takes place in the colon, at which point the absorption level is insignificant. All non-herbivorous animals almost exclusively get their vitamin B12 intake from eating other organisms.
  • Argument against Argument against If humans were not omnivores why are we attracted to the physical properties of meat?
    • Objection Objection We don't necessarily feel the need to chase down animals and feed on their flesh, do we?
      • Objection Objection That's exactly what our hunter-gatherer ancestors did for millennia.
        • Objection Objection appeal to history is not a reason.
      • Objection Objection Being omnivores or carnivores does not necessarily mean being hunters. Humans could have been scavengers.

See also[edit | edit source]

Notes and references[edit | edit source]

  1. Ludewig, Burkhard; Zinkernagel, Rolf M; Hengartner, Hans (2002-05-01). "Arterial Inflammation and Atherosclerosis". Trends in Cardiovascular Medicine 12 (4): 154–159. doi:10.1016/S1050-1738(01)00166-9. ISSN 1050-1738. http://www.sciencedirect.com/science/article/pii/S1050173801001669. 
  2. "Mechanism of colorectal carcinogenesis triggered by heme iron from red meat". Biochimica et Biophysica Acta (BBA) - Reviews on Cancer 1873 (1): 188334. 2020-01-01. doi:10.1016/j.bbcan.2019.188334. ISSN 0304-419X. https://www.sciencedirect.com/science/article/pii/S0304419X19301817. 
  3. "Meat, fish & dairy". World Cancer Research Fund. 2018-04-24. Retrieved 2020-09-23.
  4. 4.0 4.1 Bonhommeau, S.; Dubroca, L.; Le Pape, O.; Barde, J.; Kaplan, D. M.; Chassot, E.; Nieblas, A.-E. (2013-12-02). "Eating up the world's food web and the human trophic level". Proceedings of the National Academy of Sciences 110 (51): 20617–20620. doi:10.1073/pnas.1305827110. ISSN 0027-8424. https://www.pnas.org/content/110/51/20617. 
  5. 5.0 5.1 Bacha, M.; Amara, R. (2009-11-10). "Spatial, temporal and ontogenetic variation in diet of anchovy (Engraulis encrasicolus) on the Algerian coast (SW Mediterranean)". Estuarine, Coastal and Shelf Science 85 (2): 257–264. doi:10.1016/j.ecss.2009.08.009. ISSN 0272-7714. https://www.sciencedirect.com/science/article/pii/S027277140900393X. 
  6. Watts, David P.; Potts, Kevin B.; Lwanga, Jeremiah S.; Mitani, John C. (2012). "Diet of chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda, 1. diet composition and diversity". American Journal of Primatology 74 (2): 114–129. doi:10.1002/ajp.21016. ISSN 1098-2345. https://onlinelibrary.wiley.com/doi/abs/10.1002/ajp.21016. 
  7. "Primate hunting by bonobos at LuiKotale, Salonga National Park". Current Biology 18 (19): R906–R907. 2008-10-14. doi:10.1016/j.cub.2008.08.040. ISSN 0960-9822. https://www.sciencedirect.com/science/article/pii/S0960982208011172. 
  8. Lion Eats GRASS, retrieved 2021-03-16
  9. Big Cats Eat Watermelons!?, retrieved 2021-03-16
  10. Psouni, Elia; Janke, Axel; Garwicz, Martin (2012-04-18). "Impact of Carnivory on Human Development and Evolution Revealed by a New Unifying Model of Weaning in Mammals". PLoS ONE 7 (4). doi:10.1371/journal.pone.0032452. ISSN 1932-6203. PMID 22536316. PMC PMCPMC3329511. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3329511/. 
  11. Dettwyler K. A time to Wean: The Hominid Blueprint for the natural age of Weaning in Modern Human Populations. In: Stewart-MacAdam P, Dettwyler KA, editors. Breastfeeding: Biocultural Perspectives. New York: Aldine deGruyter; 1995.
  12. 12.0 12.1 "Opportunistic Organism | Encyclopedia.com". www.encyclopedia.com. Retrieved 2020-09-23.
  13. Dorward, Leejiah Jonathan (2015). "New record of cannibalism in the common hippo, Hippopotamus amphibius (Linnaeus, 1758)". African Journal of Ecology 53 (3): 385–387. doi:10.1111/aje.12197. ISSN 1365-2028. https://onlinelibrary.wiley.com/doi/abs/10.1111/aje.12197. 
  14. Dudley, Joseph P.; Hang'Ombe, Bernard Mudenda; Leendertz, Fabian H.; Dorward, Leejiah J.; Castro, Julio de; Subalusky, Amanda L.; Clauss, Marcus (2016). "Carnivory in the common hippopotamus Hippopotamus amphibius: implications for the ecology and epidemiology of anthrax in African landscapes". Mammal Review 46 (3): 191–203. doi:10.1111/mam.12056. ISSN 1365-2907. https://onlinelibrary.wiley.com/doi/abs/10.1111/mam.12056. 
  15. "Field Cameras Catch Deer Eating Birds—Wait, Why Do Deer Eat Birds?". io9. Retrieved 2021-03-16.
  16. Langman, V. A. (1978). "Giraffe Pica Behavior and Pathology as Indicators of Nutritional Stress". The Journal of Wildlife Management 42 (1): 141–147. doi:10.2307/3800701. ISSN 0022-541X. https://www.jstor.org/stable/3800701. 
  17. Furness, R. W. (1988). "Predation on ground-nesting seabirds by island populations of red deer Cervus elaphus and sheep Ovis". Journal of Zoology 216 (3): 565–573. doi:10.1111/j.1469-7998.1988.tb02451.x. ISSN 1469-7998. https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1988.tb02451.x. 
  18. Furness, R. W. (1988-11). "The predation of Tern chicks by sheep". Bird Study 35 (3): 199–202. doi:10.1080/00063658809476989. ISSN 0006-3657. http://www.tandfonline.com/doi/full/10.1080/00063658809476989. 
  19. PIETZ, P.; GRANFORS, D. (2000). "White-tailed Deer (Odocoileus virginianus) Predation on Grassland Songbird Nestlings". The American Midland Naturalist 144 (2): 419. doi:10.1674/0003-0031(2000)144[0419:WTDOVP]2.0.CO;2. ISSN 0003-0031. https://scienceblogs.com/tetrapodzoology/2010/12/20/carnivory-in-cows-and-deer. 
  20. Nack, Jamie L.; Ribic, Christine A. (2005/03). "APPARENT PREDATION BY CATTLE AT GRASSLAND BIRD NESTS". The Wilson Journal of Ornithology 117 (1): 56–62. doi:10.1676/04-056. ISSN 1559-4491. https://bioone.org/journals/the-wilson-journal-of-ornithology/volume-117/issue-1/04-056/APPARENT-PREDATION-BY-CATTLE-AT-GRASSLAND-BIRD-NESTS/10.1676/04-056.full. 
  21. Clauss, Marcus; Lischke, Andreas; Botha, Heike; Hatt, Jean-Michel (2016-02-01). "Carcass consumption by domestic rabbits (Oryctolagus cuniculus)". European Journal of Wildlife Research 62 (1): 143–145. doi:10.1007/s10344-015-0980-y. ISSN 1439-0574. https://doi.org/10.1007/s10344-015-0980-y. 
  22. "Duiker, rhymes with biker | ScienceBlogs". scienceblogs.com. Retrieved 2021-03-16.
  23. "Primate hunting by bonobos at LuiKotale, Salonga National Park". Current Biology 18 (19): R906–R907. 2008-10-14. doi:10.1016/j.cub.2008.08.040. ISSN 0960-9822. https://www.sciencedirect.com/science/article/pii/S0960982208011172. 
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  25. Watts, David P.; Mitani, John C. (2002-02-01). "Hunting Behavior of Chimpanzees at Ngogo, Kibale National Park, Uganda". International Journal of Primatology 23 (1): 1–28. doi:10.1023/A:1013270606320. ISSN 1573-8604. https://doi.org/10.1023/A:1013270606320. 
  26. "Topic: Global Meat Industry". Statista. Retrieved 2021-03-16.

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