Humans – Carnivore, Herbivore, or Omnivore, by John Coleman

John Coleman: Comparative Anatomy & Taxonomy

Comparative anatomy works on the simple and demonstrable fact that the biological form usually defines function. Human is closest to frugivore animals (fruit eaters), from the anatomic and taxonomic point of view.

Comparative Anatomy & Taxonomy

Comparative anatomy works on the simple and demonstrable fact that the biological form usually defines function. Individual features, or species may break the rules, but a look at many factors will reveal a species true biological role. Certainly science does not really validate the typical vegan diet, as this serves cultural imperatives. Science provides us with an indicator of human nutrition which was not established by culture, but is certainly that of a herbivore or frugivore and not a carnivore or omnivore.

 

Feature

Carnivore

Herbivore

Omnivore

Human

Facial Muscles

Reduced to allow wide mouth gape

Well-developed

Reduced

Well-developed

Jaw Type

Angle not expanded

Expanded angle

Angle not expanded

Expanded angle

Jaw Joint Location

On same plane as molar teeth

Above the plane of the molars

On same plane as molar teeth

Above the plane of the molars

Jaw Motion

Shearing;
minimal side-to-side motion

No shear;
good side-to-side,
front-to-back

Shearing;
minimal side-to-side

No shear;
good side-to-side,
front-to-back

Major Jaw Muscles

Temporalis

Masseter and pterygoids

Temporalis

Masseter and pterygoids

Mouth Opening vs. Head Size

Large

Small

Large

Small

Teeth: Incisors

Short and pointed

Broad, flattened and spade shaped

Short and pointed

Broad, flattened and spade shaped

Teeth: Canines

Long, sharp and curved

Dull and short or long (for defense), or none

Long, sharp and curved

Short and blunted

Teeth: Molars

Sharp, jagged and blade shaped

Flattened with cusps vs complex surface

Sharp blades and/or flattened

Flattened with nodular cusps

 

 

Feature

Carnivore

Herbivore

Omnivore

Human

Chewing

None; swallows food whole

Extensive chewing necessary

Swallows food whole and/or simple crushing

Extensive chewing necessary

Saliva

No digestive enzymes

Carbohydrate digesting enzymes

No digestive enzymes

Carbohydrate digesting enzymes

Stomach Type

Simple

Simple or multiple chambers

Simple

Simple

Stomach Acidity

Less than or equal to pH 1 with food in stomach

pH 4 to 5 with food in stomach

Less than or equal to pH 1 with food in stomach

pH 4 to 5 with food in stomach

Stomach Capacity

60% to 70% of total volume of digestive tract

Less than 30% of total volume of digestive tract

60% to 70% of total volume of digestive tract

21% to 27% of total volume of digestive tract

Length of Small Intestine

3 to 6 times body length

10 to more than 12 times body length

4 to 6 times body length

10 to 11 times body length

Colon

Simple, short and smooth,
no fermentation

Long, complex; may be sacculated, may ferment

Simple, short and smooth,
no fermentation

Long, sacculated,
may ferment

Liver

Can detoxify vitamin A

Cannot detoxify vitamin A

Can detoxify vitamin A

Cannot detoxify vitamin A

Kidney

Extremely concentrated urine

Moderately concentrated urine

Extremely concentrated urine

Moderately concentrated urine

Nails

Sharp claws

Flattened nails or blunt hooves

Sharp claws

Flattened nails

Thermostasis

Hyperventilation

Perspiration

Hyperventilation

Perspiration

 

Adapted from The Comparative Anatomy of Eating by Milton R. Mills