I recently saw a speech of Gary Yourofsky on youtube. He made the claim that humans are physiologically 100 percent herbivores. He supported his claim with the following claims:
1) The human intestine to torso ratio is 7 to13:1; the same as herbivores, while the carnivore ratio is 3 to 6:1.
2) Humans will sweat like herbivores, while carnivores pant.
3) Humans don’t have claws like herbivores, while carnivores have claws.
4) Humans have carbohydrate enzymes in their saliva like herbivores and carnivores do not.
5) Human teeth are broad, short, blunt, flat, are like herbivore and most herbivores have canine teeth.
6) The human jaw moves side to side like herbivores when it chews.
7) Humans have no carnivorous instincts.
I’m not sure about the students in his audience, but I never claimed that humans are 100 percent carnivores. I was always taught that humans are omnivores; we eat plants and animals. An omnivore would have to have a digestive system with the traits of both carnivores and herbivores. I think his claims 2 and 3 are red-herring because they have nothing to do with the digestive system; beside the fact that claim number two is false. His claim 7 is both undefined and unsubstantiated, so it is impossible to address. His claims 4, 5, and 6 prove humans are not carnivores, but don’t prove humans are not omnivores. Omnivores have to be able to breakdown plant material like an herbivore, so they would also have these traits.
I found claim one the most interesting because I own three different herbivores and thought it was time to learn their digestive systems. After a little searching, the first idea that came to my mind was that the characteristic of any given part of the system doesn’t prove anything. His first claim is basically claiming that a wagon is a type of tractor because they both have four wheels. We have to look at the digestive system as a whole.
The herbivore's digestive system is designed to turn plants into nutrition. The process used to release the nutrients is called fermentation. The herbivore's digestive system may be monogastric or ruminants. Monogastric means having a simple stomach like horses, zebra, hippopotamus, and rhinoceros, while ruminants have four part stomachs like giraffes, antelope, camels, sheep, cattle, goats, deer, and bison. In ruminants, the stomach is a large percentage of the digestive system, 60-70 percent, while in herbivores with simple stomachs the percentage is less; 8 percent for a horse. The large intestine of a ruminant is 7-12 percent of the digestive volume while in a horse it is 45 percent. The small intestines are between 15 and 30 percent with ruminants being on the smaller end of the scale. Total volume of a horse’s digestive system is 223 quarts and a sheep is 46.5 quarts. A human has a 6 quart system.
In simple stomach herbivores, fermentation takes place in the large intestine, while in ruminants it takes place in the first two parts of the stomach. Carnivores have no fermentation in their digestive system. Except for absorption of vitamins K, B-12, and biotin in the large intestine, humans have no fermentation in their digestive system either. Humans like other omnivores, and carnivores break our food down by acids while herbivores do it with bacteria.
The herbivore's digestive system is designed to turn plants into nutrition. The process used to release the nutrients is called fermentation. The herbivore's digestive system may be monogastric or ruminants. Monogastric means having a simple stomach like horses, zebra, hippopotamus, and rhinoceros, while ruminants have four part stomachs like giraffes, antelope, camels, sheep, cattle, goats, deer, and bison. In ruminants, the stomach is a large percentage of the digestive system, 60-70 percent, while in herbivores with simple stomachs the percentage is less; 8 percent for a horse. The large intestine of a ruminant is 7-12 percent of the digestive volume while in a horse it is 45 percent. The small intestines are between 15 and 30 percent with ruminants being on the smaller end of the scale. Total volume of a horse’s digestive system is 223 quarts and a sheep is 46.5 quarts. A human has a 6 quart system.
In simple stomach herbivores, fermentation takes place in the large intestine, while in ruminants it takes place in the first two parts of the stomach. Carnivores have no fermentation in their digestive system. Except for absorption of vitamins K, B-12, and biotin in the large intestine, humans have no fermentation in their digestive system either. Humans like other omnivores, and carnivores break our food down by acids while herbivores do it with bacteria.
