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; |
No shear; |
Shearing; |
No shear; |
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, |
Long, complex; may be sacculated, may ferment |
Simple, short and smooth, |
Long, sacculated, |
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