An omnivore (from Latin: omnis all; vorare to devour) is an animal that
eats both plants and meat. Omnivores lack the specialist behaviour of
carnivores and herbivores, searching widely for food sources, and are
thus better able to withstand changes within their ecological niche.
The digestive systems of omnivores reflect their versatility: they are
able to digest the cellulose of plants in the manner of herbivores but
also readily assimilate protein and other nutrients from meat [1].
Given that brain size correlates to dietary quality (nutritional and
caloric density of the diet) and omnivores have a wide-ranging diet,
this group of animals is generally an intelligent one. The history of
human evolution shows that supplementing our diet with meat allowed the
development of substantially larger brains, a process that consumes
large amounts of energy and nutrients. [2]. Other omnivorous animals
with whom humans interact-raccoons, bears and even crows-often show
remarkable intelligence in their food gathering behaviour.
http://en.wikipedia.org/wiki/Omnivore
Introduction
There are a number of popular myths about vegetarianism that have no
scientific basis in fact. One of these myths is that man is naturally a
vegetarian because our bodies resemble plant eaters, not carnivores. In
fact we are omnivores, capable of either eating meat or plant foods.
The following addresses the unscientific theory of man being only a
plant eater.
Confusion between Taxonomy and Diet
Much of the misinformation on the issue of man's being a natural
vegetarian arises from confusion between taxonomic (in biology, the
procedure of classifying organisms in established categories) and
dietary characteristics.
Members of the mammalian Order Carnivora may or may not be exclusive
meat eaters. Those which eat only meat are carnivores. Dietary
adaptations are not limited by a simple dichotomy between herbivores
(strict vegetarians) and carnivores (strict meat-eaters), but include
frugivores (predominantly fruit), gramnivores (nuts, seeds, etc.),
folivores (leaves), insectivores (carnivore-insects and small
vertebrates), etc. Is is also important to remember that the relation
between the form (anatomy/physiology) and function (behavior) is not
always one to one. Individual anatomical structures can serve one or
more functions and similar functions can be served by several forms.
Omnivorism
The key category in the discussion of human diet is omnivores, which
are defined as generalized feeders, with neither carnivore nor
herbivore specializations for acquiring or processing food, and who are
capable of consuming and do consume both animal protein and vegetation.
They are basically *opportunistic* feeders (survive by eating what is
available) with more generalized anatomical and physiological traits,
especially the dentition (teeth). All the available evidence indicates
that the natural human diet is omnivorous and would include meat. We
are not, however, required to consume animal protein. We have a choice.
The Great Apes
There are very few frugivores amongst the mammals in general, and
primates in particular. The only apes that are predominantly fruit
eaters (gibbons and siamangs) are atypical for apes in many behavioral
and ecological respects and eat substantial amounts of vegetation.
Orangutans are similar, with no observations in the wild of eating
meat.
Gorillas are more typically vegetarian, with less emphasis on fruit.
Several years ago a very elegant study was done on the relationship
between body size and diet in primates (and some other mammal groups).
The only primates on the list with pure diets were the very small
species (which are entirely insectivorous) and the largest (which
specialize in vegetarian diet). However, the spectrum of dietary
preferences reflect the daily food intake needs of each body size and
the relative availability of food resources in a tropical forest. Our
closest relatives among the apes are the chimpanzees (i.e.,
anatomically, behaviorally, genetically, and evolutionarily), who
frequently kill and eat other mammals (including other primates).
Evidence of Humans as Omnivores
Archeological Record
As far back as it can be traced, clearly the archeological record
indicates an omnivorous diet for humans that included meat. Our
ancestry is among the hunter/gatherers from the beginning. Once
domestication of food sources began, it included both animals and
plants.
Cell Types
Relative number and distribution of cell types, as well as structural
specializations, are more important than overall length of the
intestine to determining a typical diet. Dogs are typical carnivores,
but their intestinal characteristics have more in common with
omnivores. Wolves eat quite a lot of plant material.
Fermenting Vats
Nearly all plant eaters have fermenting vats (enlarged chambers where
foods sits and microbes attack it). Ruminants like cattle and deer have
forward sacs derived from remodeled esophagus and stomach. Horses,
rhinos, and colobine monkeys have posterior, hindgut sacs. Humans have
no such specializations.
Jaws
Although evidence on the structure and function of human hands and
jaws, behavior, and evolutionary history also either support an
omnivorous diet or fail to support strict vegetarianism, the best
evidence comes from our teeth.
The short canines in humans are a functional consequence of the
enlarged cranium and associated reduction of the size of the jaws. In
primates, canines function as both defense weapons and visual threat
devices. Interestingly, the primates with the largest canines (gorillas
and gelada baboons) both have basically vegetarian diets. In
archeological sites, broken human molars are most often confused with
broken premolars and molars of pigs, a classic omnivore. On the other
hand, some herbivores have well-developed incisors that are often
mistaken for those of human teeth when found in archeological
excavations.
Salivary Glands
These indicate we could be omnivores. Saliva and urine data vary,
depending on diet, not taxonomic group.
Intestines
Intestinal absorption is a surface area, not linear problem. Dogs
(which are carnivores) have intestinal specializations more
characteristic of omnivores than carnivores such as cats. The relative
number of crypts and cell types is a better indication of diet than
simple length. We are intermediate between the two groups.
Conclusion
Humans are classic examples of omnivores in all relevant anatomical
traits. There is no basis in anatomy or physiology for the assumption
that humans are pre-adapted to the vegetarian diet. For that reason,
the best arguments in support of a meat-free diet remain ecological,
ethical, and health concerns.
http://www.vrg.org/nutshell/omni.htm
An omnivore is a kind of animal that eats either other animals or
plants. Some omnivores will hunt and eat their food, like carnivores,
eating herbivores and other omnivores. Some others are scavengers and
will eat dead matter. Many will eat eggs from other animals.
Omnivores eat plants, but not all kinds of plants. Unlike herbivores,
omnivores can't digest some of the substances in grains or other plants
that do not produce fruit. They can eat fruits and vegetables, though.
Some of the insect omnivores in this simulation are pollinators, which
are very important to the life cycle of some kinds of plants.
http://www.qrg.northwestern.edu/projects/marssim/simhtml/info/whats-an-omnivore....
> No essence. No permanence. No perfection.
