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 omnivoresEdit

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

  •   Argument forHumans gain significant nutrition and energy from meat.
    •   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 AND anatomical carnivores/omnivores do not develop such issues, this is an argument about anatomy, behavior only tells us what we already know, and I think we are all accutely aware that meat eating is a common practice, but so is traveling via airplane; the fact that so many of us do this however, doesn't mean we have specific physiological adaptations towards this behavior.[2][3]
  •   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 — 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 — 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 — Only a tiny portion of their diet comes from meat, they don't appear to have specific physiological adaptations to the eating of meat, and insectivory is often thought of as being distinct from run of the mill carnivory even tho insects are still in the kingdom of animalia
    •   Objection — They still engage in the act of eating meat so going by their behavior they are still omnivorous and not herbivorous,
      •   Objection — Carnivores have also been reported eating plants.[8][9] They are carnivores nonetheless. The taxonomic classification of omnivore/herbivore/carnivore, is something that biologists have a tendency to make based exclusively on behavior without placing that much weight on anatomy, especially in cases where reports of certain behaviors have their severity or frequency exagerated because they believe them to be out of the norm.
  •   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 — Many herbivores wean earlier than humans, such as cattle and sheep.
  •   Argument for — Humans are able to digest meat and absorb its nutrients, which we would be unable to do if we were herbivores.
    •   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 — 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.

  Objection — This ignore's the portion of the prior argument which mentions animals with the taxonomic classification of herbivory occasionally eating meat yet retaining their classification, and that upon mentioning these animals occasional pedatory behaviors, there was no mention of them experiencing indigestion as a result. Meat is in general, easier to digest than plants on account of being biochemically simpler, and carnivore digestive tracts are often described as being simpler and in some cases described as being more primitive. If specialized adaptations are unecessary to derive nutrition from meat, then being able to derive nutrition from it does not preclude one from being herbivorous.

  •   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 — Many predators don't have forward-facing eyes, and many herbivores have forward-facing eyes.
    •   Objection — Humans descend from tree-dwelling animals, that needed precise forward-looking binocular vision to avoid falling when leaping and moving around.
  •   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 — 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 — 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 — 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 — 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 — 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.

  Objection — Only anatomical herbivores develop atherosclerosis when exposed to high levels of saturated fat and cholesterol, animals with sufficient physiological adaptations to eating meat do not share this trait. We can cook things vegetables and eat them without negative effects on our health, the fact that there are well documented negatives from the consumption of meat which pesist even after cooking it mean its just not what's best for our anatomy, which it just so happens, at least in this regard takes after hebivory.

  •   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 — 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]

  Objection — Sounds like a bunch of word salad, if one wants to determine whether humans have certain genetic traits its better to just look at their genes rather than attending a dog eating festival in Asia and basking in how similar it is to the state fairs in North America where everyone eats hot dogs instead of the real thing. Forgive any lack of professionalism here if it seaped out, but this argument is silly, as far as I know, the human genome has already been sequenced, speculations based on culture are no longer necessary and would only serve as a distraction from more important points of discussion.

Humans are herbivoresEdit

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

Arguments forEdit

  •   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 — Anchovy subsist primarily on zooplankton.[5] Pigs are omnivores. This suggests that humans are omnivores rather than herbivores.
  •   Argument for — Some of our closest evolutionary cousins (chimpanzees, bonobos, gorillas) are herbivores.
    •   Objection — Chimps and bonobos frequently eat termites, ants and other insects, which are still meat.
    •   Objection — Chimps have been documented hunting and eating small mammals.[25]
      •   Objection — This doesn't make them omnivores, but opportunistic feeders.[12]
  •   Argument for — Humans lack claws, sharp teeth or other natural weapons.
    •   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 — Our natural weapon is our brain, which can and is used to make other weapons and strategies.
      •   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 — 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 — 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 — 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 againstEdit

  •   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 — 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.

  Objection — There are different subcategories of herbivores, folivores derive most of their energy from foliage, whereas frugivores derive most of their energy from fruits, frugivores often are monogastic rather than ruminant animals, and they also have a very limited ability to digest celluose, instead their microbiome ferments it and produces metabolites which aid in digestion or offer other benefits to the organism. Humans basically have traits of frugivores but are unique in our ability to digest starches more efficiently, a typical starch-eating animal not only eats it raw but has much less salivary amylase than a human; humans secrete 3 times more salivary amylase than the other great apes, which allows from up to 40% of the breaking down of starch into glucose to happen in the mouth and the rest to be handled by the pancreas. This is a specific adaptation to the consumption of a plant based energy source

  •   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 — 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 — 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.[citation needed]

  Objection — Neither can cattle in the age of chlorinated watter and those are often touted as being the strictest herbivores of all, they are often given b-12 supplements and that's the primary reason why skeletal muscle tissue found in supermarkets contains ample levels of b12. And of course non-herbivorous animals almost exlusively get their vitamin b12 from the consumption of other animals, carnivorous animals often consume the contents of the digestive tracts of such animals, sometimes even going so far as to consume the contents of the colon which is the most concentated source of bacteria which produce B12, omnivores often have similar dietary patterns when chowing down on carcases. Even if an omnivore were to consume more vegetation than animal flesh, fecal matter from the contents of another animals colon is a much more concentrated source than leaves with dirt.

  •   Argument against — If humans were not omnivores why are we attracted to the physical properties of meat?
    •   Objection — We don't necessarily feel the need to chase down animals and feed on their flesh, do we?
      •   Objection — That's exactly what our hunter-gatherer ancestors did for millennia.
        •   Objection — appeal to history is not a reason and they didn't necessarily do that because they were salivating at the mouth thinking of biting into raw deer hide at least, that's not what one would think if one projects one's taste preference for cooked meat onto ancient peoples; one can only speculate, since there is limited data but its likely that was done largely due to the scarcity of calories from ANY source, plant OR animal which demanded that they not be too picky about where their next meal came from. A baby doesn't salivate and think of killing a small animal like a rabbit or turtle when presented with one but will eat or try to eat something like an apple or a bannana most lkely. On the other hand, the desire to hunt is embedded is so deeply embeded in a kitten that they will chase mice or toys humans have fashioned to look like them even in their infancy and without being instructed to do so.
      •   Objection — Being omnivores or carnivores does not necessarily mean being hunters. Humans could have been scavengers.

See alsoEdit

Notes and referencesEdit

  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. 
  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. 
  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. 
  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. 
  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. 
  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. 
  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. 
  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 |". 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. 
  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. 
  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. 
  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. 
  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. 
  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. 
  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. 
  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. 
  22. "Duiker, rhymes with biker | ScienceBlogs". 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. 
  24. 24.0 24.1 Craig, David P. (1998). "Chipmunks Use Leverage to Eat Oversized Eggs: Support for the Use of Quail Eggs in Artificial Nest Studies". The Auk 115 (2): 486–489. doi:10.2307/4089210. ISSN 0004-8038. 
  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. 
  26. "Topic: Global Meat Industry". Statista. Retrieved 2021-03-16.

External linksEdit