Friday, August 27, 2010

List of Physiological Features Indicating Humans are Herbivores

 The dumbest, most cliché thing you could possibly say to a vegetarian: "Hey! So, if we weren't meant to eat meat, what are these for?" (Then point to canine teeth.)

I get stupid comments like that all the time. This list is for those people. And to answer that question (hopefully once and for all, but I'm not holding my breath), those teeth are for display purposes only, with a minimal amount of usefulness in such activities as cracking open seeds and nuts and tearing the rind off of fruit. I challenge you to go take down a buffalo with average human canines. And I'm not joking.

As far as why so many humans are actually eating meat now, that's a question best answered by society and culture rather than biology, but I'll save that for another day. To the list...

Facial Muscles
Carnivore--Reduced to allow wide mouth gape

Jaw Type
Carnivore--Angle not expanded
Herbivore--Expanded angle
Omnivore--Angle not expanded
Human-----Expanded angle

Jaw Joint Location
Carnivore--On same plane as molar teeth
Herbivore--Above the plane of the molars
Omnivore--On same plane as molar teeth
Human-----Above the plane of the molars

Jaw Motion
Carnivore--Shearing; minimal side-to-side motion
Herbivore--No shear; good side-to-side, front-to-back
Omnivore--Shearing; minimal side-to-side
Human-----No shear; good side-to-side, front-to-back

Major Jaw Muscles
Herbivore--Masseter and pterygoids
Human-----Masseter and pterygoids

Mouth Opening vs. Head Size

Teeth (Incisors)
Carnivore--Short and pointed
Herbivore--Broad, flattened and spade shaped
Omnivore--Short and pointed
Human-----Broad, flattened and spade shaped

Teeth (Canines)
Carnivore--Long, sharp and curved
Herbivore--Dull and short or long (for defense), or none
Omnivore--Long, sharp and curved
Human-----Short and blunted

Teeth (Molars)
Carnivore--Sharp, jagged and blade shaped
Herbivore--Flattened with cusps vs complex surface
Omnivore--Sharp blades and/or flattened
Human-----Flattened with nodular cusps

Carnivore--None; swallows food whole
Herbivore--Extensive chewing necessary
Omnivore--Swallows food whole and/or simple crushing
Human-----Extensive chewing necessary

Carnivore--No digestive enzymes
Herbivore--Carbohydrate digesting enzymes
Omnivore--No digestive enzymes
Human-----Carbohydrate digesting enzymes

Stomach Type
Herbivore--Simple or multiple chambers

Stomach Acidity
Carnivore--Less than or equal to pH 1 with food in stomach
Herbivore--pH 4 to 5 with food in stomach
Omnivore--Less than or equal to pH 1 with food in stomach
Human-----pH 4 to 5 with food in stomach

Stomach Capacity
Carnivore--60% to 70% of total volume of digestive tract
Herbivore--Less than 30% of total volume of digestive tract
Omnivore--60% to 70% of total volume of digestive tract
Human-----21% to 27% of total volume of digestive tract

Length of Small Intestine
Carnivore--3 to 6 times body length
Herbivore--10 to more than 12 times body length
Omnivore--4 to 6 times body length
Human-----10 to 11 times body length

Carnivore--Simple, short and smooth
Herbivore--Long, complex; may be sacculated
Omnivore--Simple, short and smooth
Human-----Long, sacculated

Carnivore--Can detoxify vitamin A
Herbivore--Cannot detoxify vitamin A
Omnivore--Can detoxify vitamin A
Human-----Cannot detoxify vitamin A

Carnivore--Extremely concentrated urine
Herbivore--Moderately concentrated urine
Omnivore--Extremely concentrated urine
Human-----Moderately concentrated urine

Carnivore--Sharp claws
Herbivore--Flattened nails or blunt hooves
Omnivore--Sharp claws
Human-----Flattened nails

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