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]

Omnivores are organisms that feed on both animal tissue and plants.

  • Argument Argument Humans have a trophic level of 2.21 (same as anchovy and pigs)[1] Anchovy subsist primarily on zooplankton, [2] which are generally crustaceans and jellies.[3] Pigs are omnivores.[4] It is suggested that animals with such a trophic level can subsist on a widely varied diet.
  • Argument Argument Our closest evolutionary relatives, chimpanzees (Pan troglodytes) and bonobos (P. paniscus), are omnivorous. [5] as these species' biology most closely resembles that of Homo sapiens, it is more likely that humans share commonalities in digestive physiology.
    • Objection Objection A study from Scientific America states that chimps eat meat on average 9 days a year and bonobos even less. 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.
  • Argument Argument Humans wean earlier than herbivores, a pattern that matches that of carnivores.[6] 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 2.5 years old, which is considerably shorter than in chimpanzees and orangutans, even accounting for cultural differences and individual preferences.
  • Argument Argument Humans are able to digest meat and absorb its nutrients, which we would be unable to do if we were herbivores.
    • Objection Objection Even if humans are able to eat other animals, it does not mean it's best if they do so.
      • Objection Objection That's not an argument regarding if humans are omnivores or herbivores, that's just a statement of uncertainty. What's "best" doesn't even enter into the discussion.
  • Argument Argument 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, need a correct example. (Lemurs eat insects, and are not herbivores). (Aegyptopithecus) that got it in the first place because of the "X-ray vision" advantage.[7] Humans descend from tree-dwelling animals, that needed precise forward-looking binocular vision to avoid falling when leaping and moving around.
  • Argument Argument 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 There is no way to separate behaviour from physiology or biology. All behaviour and will, including feeding behaviour has some kind of biological and physiological basis.
      • Objection Objection For the most part, "omnivory", "carnivory" & "herbivory" have historically been defined by behavioural measures. Numerous species that have previously been defined as herbivores, including: Hippopotomus [8][9], white tailed deer [10], giraffe warthog and waterbuck [11], sheep [12][13] cattle [14][15], rabbits [16], duikers [17], bonobos [18], chipmunks [19], and squirrels [20] (not an exhaustive list) have been shown through behavioural observation, or through fecal and stomach content analysis (both the result of behaviour) 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 categorisation from herbivore to omnivore, or at the very least "Partially omnivorous". If other animal species are defined by their behavioural diet, than so must humans.
    • 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?
  • Argument Argument 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]

Herbivores are organisms that feed exclusively or mainly on plants.

  • Argument Argument 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.[21]
    • Objection Objection The conclusion that humans are herbivorous does not follow from this argument or the citation. The cited paper states "This first estimate of HTL at 2.21, i.e., a trophic level similar to anchoveta and pigs, quantifies the position of humans in the food web.[22] Anchoveta (Anchovy) subsist primarily on zooplankton [23], which are generally crustaceans and jellies [24]. Pigs are omnivores [25]. This is in fact, an argument against human herbivory and for human omnivory.
  • Argument Argument Some of our closest evolutionary cousins (bonobos, gorillas) are herbivores.
    • Objection Objection Chimpanzees have been documented hunting, killing and eating monkeys.
    • Objection Objection Bonobos are omnivorous and predate on other animals [26]
    • Objection Objection Great apes will occasionally eat animal matter like insects or carrion.
  • Argument Argument Humans lack claws, sharp teeth or other natural weapons.
    • 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 ObjectionCompassion 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. [27]
  • Argument Argument 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.
  • 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.
    • 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.
      • Objection Objection This is WRONG. Any 1st year biology student knows this. GOOGLE it for .... We cannot break down cellulose, AT ALL. (Even though we cannot digest cellulose, we find many uses for it including: Wood for building; paper products; cotton, linen, and rayon for clothes; nitrocellulose for explosives; cellulose acetate for films.)[28]
  • 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. [citation needed]
  • Argument against Argument against Humans have a 3 times reduced ability to synthesize taurine compared to herbivores.[citation needed]
  • Argument against Argument against Humans selectively absorb heme iron in the small intestine with specialized receptors, which no herbivore does.[citation needed]
  • 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 Why would I do that when there is readily available meat at the market? If we lived in a different era or environment we certainly would hunt.

See also[edit]

Notes and references[edit]

  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" (in en). 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. 
  2. https://www.sciencedirect.com/science/article/pii/S027277140900393X
  3. https://en.wikipedia.org/wiki/Zooplankton
  4. https://en.wikipedia.org/wiki/Pig
  5. https://www.sciencedirect.com/science/article/pii/S0960982208011172
  6. 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/. 
  7. Changizi, Mark A.; Shimojo, Shinsuke (2008-10-21). ""X-ray vision" and the evolution of forward-facing eyes". Journal of Theoretical Biology 254 (4): 756–767. doi:10.1016/j.jtbi.2008.07.011. ISSN 1095-8541. PMID 18682253. https://www.ncbi.nlm.nih.gov/pubmed/18682253. 
  8. https://onlinelibrary.wiley.com/doi/abs/10.1111/aje.12197
  9. https://onlinelibrary.wiley.com/doi/abs/10.1111/mam.12056
  10. https://io9.gizmodo.com/field-cameras-catch-deer-eating-birds-wait-why-do-deer-1689440870
  11. https://www.jstor.org/stable/3800701?seq=1#page_scan_tab_contents
  12. https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1988.tb02451.x
  13. https://www.tandfonline.com/doi/pdf/10.1080/00063658809476989
  14. https://scienceblogs.com/tetrapodzoology/2010/12/20/carnivory-in-cows-and-deer
  15. 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.short
  16. https://link.springer.com/article/10.1007/s10344-015-0980-y
  17. https://scienceblogs.com/tetrapodzoology/2008/08/08/duiker-rhymes-with-biker
  18. https://www.sciencedirect.com/science/article/pii/S0960982208011172
  19. https://www.jstor.org/stable/4089210?seq=1#page_scan_tab_contents
  20. https://www.jstor.org/stable/4089210?seq=1#page_scan_tab_contents
  21. 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" (in en). 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. 
  22. 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" (in en). 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. 
  23. https://www.sciencedirect.com/science/article/pii/S027277140900393X
  24. https://en.wikipedia.org/wiki/Zooplankton
  25. https://en.wikipedia.org/wiki/Pig
  26. https://www.sciencedirect.com/science/article/pii/S0960982208011172
  27. cycles, This text provides general information Statista assumes no liability for the information given being complete or correct Due to varying update; Text, Statistics Can Display More up-to-Date Data Than Referenced in the. "Topic: Global Meat Industry". www.statista.com. Retrieved 2019-11-06.
  28. http://chemistry.elmhurst.edu/vchembook/547cellulose.html

External links[edit]