Question

Humans are bipedal, terrestrial omnivores. As a species, we are adapted to quite a range of habitats, from deserts to mountains and from rain forests to tundra. Ultimately, however, we are descended from early hominids who evolved in African plains, and our body systems tend to reflect this. Your job is to determine how humans might be adapted to specific environments if they had evolved to eat a herbivorous diet (grasses or leaves).

Write a brief description of the digestive system, and why it would look the way it does. Consider the following:

• What would be required to eat, chew, swallow, break-up, digest, and extract nutrients? You are encouraged to look up other (non-human; can be non-mammalian) animals that share this diet for ideas.
• What if humans were not omnivores, but had evolved for a different food source? In other words, it would still look *basically* like a human but would have some important differences related to its diet.
• What would the digestive system of a human that adapted to a different food system look like, and why would it look like this?
• You should consider the following parts of the digestive system in your answer: Mouth & teeth, Stomach & upper digestive tract (including crop & gizzard if relevant), Intestines, and Accessory organs (spleen, gall bladder, liver).

Answer 1

Humans are generally omnivorous can eat both plants and meats. If human is converted to eat only the plant materials such as grasses and leaves may lead to evolve as a herbivorous animal. So many anatomical changes will occur in the body based on the diet. They can prefer eat only leaves(Folivores), fruits (Frugivore) , seeds (Granivore) or all on the availability. But in general the following changes will occurs on anatomically

Mouth and Teeth

• Cellulose is the main organic component of the plant material and it is very hard to digest. Cellulose is the primary component in plant cell wall.
• So it is hard to chew and break down many pairs flattened, ridged and strong molars help to grind leaves and shoots very effectively.
• Jaws capable of moving side ways or rotatory
• Canine is reduced or completely absent it is not important in chewing purpose
• Incisors may be only in the lower jaws (Deer) or both (horse)

Stomach

• Several stomach chambers is required to digest the food. For example Ruminants have different chamber and they regurgitate food called Cud. Will move to other chamber and regurgitate then it moves to 3rd chamber and so on.
• Mastication and rumination is important in them.
• Stomach is larger compared to human. The capacity can increase in to 8 1/2 gallons (Sheep) than 4 pints in human.
• The digestion mostly from 12 to 48 hours can take so the stomach will not empties. So no inter digestive rest.
• Protozoa and bacteria is present it is essential for digestion.
• Bacterial flora is fermentative but putrifactive in human
• Gastric acidity will be weak
• Long intestine about 20 times larger than body length.
• colon long and complex acids.
• Long caecum and have vital role in digestion. Which store food material help to digest by bacteria.
• Gross food in faeces after digestion is large amount.

Gall bladder

• Do not have or poorly developed gall bladder. Because herbivores do not eat fat fat in regular basis so they need not require much amount of bile to emulsify food.

Pancreas

• Partial digestion from pancreas

If human is not an omnivorous they could be in different in diet may not be related with their structural posture. For example Gorilla is a frugivore can eat fruits by its hands and we can also acquire food by plucking by hands likes what we now doing. But the enzymes and mechanisms will be changed gradually. But as we are omnivores a higher difference may not be seen if we change into frugivory or granivory.

• The digestive system will be change in a smaller way if we change to another diet completely. Because body is require different mechanisms and enzymes for digestion and absorption.