Humans are herbivorous by nature based on biological evidence. Humans have longer digestive tracts, weaker jaws and nails, and teeth adapted for grinding plant material unlike carnivores. While early human ancestors ate mostly fruits and bugs, meat became a larger part of the diet more recently. A high meat diet is linked to many modern health issues, and humans are one of the only species that cooks meat for safe consumption. Overall, the evidence suggests humans are best suited for low meat, plant-based diets.

1. Are Humans Vegetarians By Nature?

2. Statement of Reason
Given scientific data on human biology, the theory of
evolution, and scientific studies on what are
documented as human ancestors from the past and
recent history, it stands to reason that humans are
herbivorous (vegetarian) by nature

3. Biological Overview
• Humans have longer digestive tracts
• The teeth and jaw of homo sapiens are just recently
starting to adapt to that of an omnivorous diet
• The jaw, legs, and nails of humans are not strong
enough to capture and immobilize prey without the use
of tools
• All flesh-eating animals can naturally digest their prey
raw, and crave and consume it without seasoning or
preparing it in any fashion

4. A satirical
vegetarian-geared
comic based on
many of the
prominent
biological features
humans do not
have that other
land based
carnivores do
Artist Unknown

5. Digestive Tract
• Carnivores and omnivores have shorter intestines
• Natural meat-eaters have larger stomach capacity
• Stomach acidity in Humans is 20 times weaker than
in carnivores
• Meat needs to digest rapidly, otherwise it will rot
inside the intestinal tract
• Human’s well developed salivary glands are for
breaking down fruits, vegetables, and grains
• Carnivores swallow whole pieces of flesh, and
sometimes, entire animals

6. Digestive Tract
Reference Milton R. Mills, (2009)

7. Teeth and Jaw
• Human teeth are mostly
flat for grinding and
extensive chewing
• Humans have a
carbohydrate digestive
enzyme in their mouth
• Homo sapiens teeth have
adapted more to break
down plant material
• Carnivores have stronger
jaws for tearing flesh
Reference Lewin and Foley, (2004)

8. Teeth and Jaw
In the 2004 edition of “Principles of Human
Evolution,” Lewin and Foley point out that “Only
with the evolution of Homo ergaster (erectus) 1.9
million years ago does the toothwear pattern
make a shift, perhaps indicating the inclusion of a
significant amount of meat in the diet”

9. Teeth and Jaw for Chewing
Reference Milton R. Mills, (2009)

10. Legs, Jaw, and Nails
• Mills (2009) asserts that “An animal which captures, kills
and eats prey must have the physical equipment which
makes predation practical and efficient”
• Human jaw cannot withstand tearing into natural,
unprepared flesh
• Carnivore nails, or claws, are sharp for helping kill and
rip apart prey
• Humans do not have the leg strength or endurance to
constantly chase prey

11. Jaw and Nail Structure
Reference Milton R. Mills, (2009)

12. Early Human Ancestors
• Eaton and Konner (1985) state that “From about 24
to 5 million years ago fruits appear to have been the
main dietary constituent for hominids...since 4.5
million years ago our ancestral feeding pattern
included increasing amounts of meat.”
• The term hominids refers to early cross-evolution
species of humans closest to apes
• Lizard and bug remnants are most commonly found
“meat” particles in fossilized teeth from human
ancestors

13. Modern Human Ancestors
• The vast inclusion of meat in human diet did not
erupt until between the 16th and 18th centuries
• Meat must be cooked to consume in larger quantities
safely, contrary to that of carnivores, which will not
consume “cooked” meat in the wild, such as that
from a forest fire
• Develop more diseases and health issues related to
meat products than any other dietary item

14. Modern Human Necessity
• Even modern food pyramids
indicate that meat intake is
one of the lowest
requirements of human diet,
and can be substituted with
legumes, nuts, and seeds
• The National Cancer Institute
estimates 3 out of 4 health
and disease related deaths
are caused by improper diet

15. Did You Know?
• Dr. John Harvey Kellogg, inventor of the ever-so
popular “Corn Flakes,” also “invented” modern day
vegetarianism
• Dr. Kellogg maintained that a low protein diet
strengthened resistance to disease, promoted
longevity, and increased physical and mental
endurance; whereas a high protein diet overtaxed
the kidneys and liver, and contributed to the
accumulation of toxins in the intestines
• As a surgeon, he restricted his patients to a
vegetarian diet weeks before surgery

16. Conclusion
• Human biology is most similar to herbivores, and is
only recently adapting to a more omnivorous diet
• Highly carnivorous diet in humans attributes to an
estimated 75% of health related deaths and issues
such as heart disease, stroke, cancer, diabetes, and
high blood pressure
• “While carnivores take pleasure in killing animals and
eating their raw flesh, any human who killed an
animal with his or her bare hands and dug into the
raw corpse would be considered deranged”

17. Bibliography
• “The Comparative Anatomy of Eating,” Vegsource, Milton R. Mills, (2009)
• “Fit Food For Humanity,” Natural Hygiene Press, no author cited (1982)
• “Teeth of the Earlier Forms of Prehistoric Man,” Arthur Keith (1913)
• “Paleolithic Nutrition: a Consideration of its Nature and Current
Implications,” The New England Journal of Medicine, Boyd Eaton and
Melvin Konner (1985)
• “Principles of Human Evolution,” Roger Lewin and Robert Foley (2004)
• “The Vegetable Passion,” Janet Barkas, (1975)
• National Cancer Institute
• GoVeg.com