Wheat-Eaters or Meat-Eaters?

by Dr Jeanette Di Leo

A common counter-argument to vegetarianism or veganism is that we humans have supposedly evolved to eat meat. If that is true, then one would expect us to have more morphological and physiological traits in common with carnivores or omnivores than with herbivores.

For further information see our Wheat-Eaters or Meat-Eaters guide.

As you can explore in the table below, that is not the case. 

Click on each topic to find out more.

CARNIVORE
Diets compared

OMNIVORE
Diets compared

HERBIVORE
Diets compared

HUMAN
Diets compared

Buccinator muscle (‘cheek muscle’) (buccinator)

Allows wide mouth gape

Allows wide mouth gape

Assists in mastication

Assists in mastication

Jaw type and jaw-closing muscles (jawtype)

Angle not expanded

 

M. temporalis >> M. masseter

Angle not expanded

 

M. temporalis >> M. masseter

Expanded angle

 

M. temporalis << M. masseter

Expanded angle

 

M. temporalis > M. masseter

Jaw joint location (jawtype)

On the same plane as the molars

On the same plane as the molars

Above the plane of the molars

Above the plane of the molars

Jaw motion (jawmotion)

Slicing; minimal side-to-side motion

Slicing; minimal side-to-side motion

No slicing; good side-to-side, front-to-back motion

No slicing; good side-to-side, front-to-back motion

Gape (buccinator)

Large

Large

Small

Small

Teeth: incisors (teeth)

Short and pointed

Short and pointed

Broad, flattened and spade-like

Broad, flattened and spade-like

Teeth: canines (teeth)

Long, sharp and curved

Long, sharp and curved

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

Short and blunted

Teeth: molars (teeth)

Sharp, jagged, and blade-shaped

Sharp blades and/or flattened

Flattened to crush and grind food

Flattened to crush and grind food

Chewing (Mastication) (jawmotion)

Hardly; swallows food whole

Swallows food whole and/or simple crushing

Extensive chewing necessary to process tough plant matter

Extensive chewing necessary to process tough plant matter

Saliva (saliva)

Small parotid salivary gland

 

 

Mucous submandibular saliva

Intermediate to large parotid salivary gland

 

Seromucous submandibular saliva

Large parotid salivary gland

 

 

Mostly serous submandibular saliva

Large parotid salivary gland

 

 

Mostly serous submandibular saliva

Length of digestive tract

Only 2 to 5 times body length (so that rapidly decaying meat can pass out of the body quickly)

Highly variable: between 1.25 and 10 times the body length

7 to more than 20 times body length; allows more time for the breakdown and absorption of nutrients from plant foods

Around 7 times the body length

Colon (colon)

Simple, short, and smooth

Variable across species: short and smooth or medium-sized and sacculated

Long, complex; may be sacculated

Long and sacculated

Body cooling technique (bodycooling)

Panting

Panting

Sweating

Sweating

 

 

What about humans?

As you can see, of the 13 physiological and morphological characteristics we have examined, humans share 12 with herbivores. There are no traits to suggest that we have evolved or adapted to consume meat.

 

Table adapted from Mills, Milton R. "The Comparative Anatomy of Eating." VegSource Interactive Inc., 26 (1996).