Are humans omnivores or herbivores?

Resource type : this resource is a wikidebate .

Subject classification : this is a biology resource.

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? Or maybe even carnivores?

Humans are omnivores[ edit ]

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

•  Argument Humans, like other predators have forward facing eyes rather than having eyes on the side of our head as prey would. This would imply that we were designed to hunt and eat other species.
  •  Objection This can be explained by the fact that humans descend from tree-dwelling animals, that needed precise forward-looking binocular vision to avoid falling when leaping and moving around.
•  Argument The vast majority of humans practice an omnivorous diet, 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. This would be self-proclaimed and removes all meaning to the actual question omnivores vs herbivores.
•  Argument Humans have been eating considerable amounts of both animal and plant matter for millions of years.
  •  Objection Doing something is not the same as being physiologically optimized for it. This only describes man’s will and is therefore irrelevant for a question of human physiology (just like the previous argument).
•  Argument Humans wean earlier than herbivores, a pattern that matches that of carnivores. ^[1]
  •  Objection This is highly cultural and mostly determined by the decision of the mother. The modern society strongly influences the reduction of weaning time. Besides, pediatrics rarely agree on how long a baby should be fed breast milk.
    •  Objection 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. So even accounting for cultural differences, humans still wean much earlier than other apes. ^[2]
•  Argument Human omnivory is a cultural universal, making it part of the human species as a whole.
  •  Objection Culture has nothing to do with physiology until otherwise demonstrated.

Humans are herbivores[ edit ]

Herbivores are organisms that feed exclusively or mainly on plants.

•  Argument Our closest evolutionary cousins (chimpanzees, bonobos, gorillas) are all herbivores.
  •  Objection All great apes are actually omnivores; they’re mostly plant-biased omnivores, hence the confusion, but they do still eat animal matter.
•  Argument Humans lack claws, sharp teeth or other natural weapons.
  •  Objection Our evolutionary adaptation is our brain, namely to make suitable weapons and strategies; this adaptation is a valid evolutionary strategy, and should not be discounted. Complex tool-making is intrinsically part of the human species.
•  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. It should exclude the neck or a giraffe would spoil the metrics. The ratio is therefore 10.15. Herbivores are known to have an intestinal tract of 10 to 12 times their chest length.
•  Argument against Humans can’t derive energy from cellulose due to a reduced cecum and colon; all other herbivores and plant-biased omnivores (e.g. great apes, pigs) can do this.
  •  Objection Herbivores do not create any enzyme that breaks down cellulose. Instead, they eat food that contains these enzymes.
•  Argument against Humans require vitamin B12 in their diet, unlike herbivorous animals which can make their own in their colon with the help of bacteria.
  •  Objection All animals and humans create vitamin B12 in their feces. In fact they don’t, a bacteria does. 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.
•  Argument against Humans have a 3 times reduced ability to synthesize taurine compared to herbivores.
•  Argument against Humans selectively absorb heme iron in the small intestine with specialized receptors, which no herbivore does.
  •  Objection Please provide reference to a study where someone tried to give a steak to a herbivore to see if they adsorb heme iron. Nutritionist for 16 years and I never heard of a such study. This seems like a assumption without substance.

Notes and references[ edit ]

External links[ edit ]

• Humans are not herbivores – Vegan biologist argues humans are omnivores
• Are humans omnivores, carnivores or herbivores? – Video discussing the issue
• Image comparing the mouth and teeth of various species of animals

• Wikidebates
• Biology
• Food