week 4- Comparative Primates

Primitive Comparative Blog Post

Dentition is the development of teeth and their arrangement in the mouth. The characteristics are the kind and the number of teeth in a given species. Primates have four types of teeth… Incisors are like tiny shovels or spatulas that cut food. Canines are generally pointed, stabbing teeth that can serve as weapons in most primates. Premolars and molars have large crown surfaces that shear and crush food during mastication.

3a) ENVIRONMENT:

As you read through our primates and their dentition characteristics and traits you will notice they all have something in common, they are omnivores. It is my belief that they eat a mixture of plants and meat (mostly plants and alike) because of their environment. They all share a common environment called the rain forest to inhabit. They regions may vary from country to country, coastline to coastline, but they all live in a tropical environment that feeds on plants, seeds, plant matter, and alike. In order to understand their dentition and why it is formed the way it is we must understand, simply, what a rain forest is. The forest grows in a narrow zone close to the equator. The equators have more direct sunlight hitting the lands and sea that any other part of the world. The largest tropical rain forest is known to be the Amazon which lies in South America. Because the rain forest are being cut down and destroyed; most animals and plant life that call the rain forest home are endangered. The seasons in a rain forest do not change. It is hot and wet all year round. The average temperature is 80 degrees (f) and the humidity levels are 90-100% yearly. The tropical rain forest is known to be the wettest place on Earth with an average rain fall of 100-400 inches per year which equals to approximately 9-30 ft of rain/yr. The rainforest is able to create this climate because it recycles its rain! The water evaporates from the forest back into the air and forms clouds above the forests canopy and then the clouds erupt once again causing rainfall and the cycle is continuous. As we continue reading about the dentition traits and characteristics of our primates, we will better understand why they have a diet as they do, why they focus on specific choices of food, and perhaps why their teeth and mouth formation is how it is  =).

Lemurs: Known to live only in Madagascar and Comoro Islands off the coast of Africa. Madagascar is an island in the Indian Ocean off the coast of Africa. Millions of years ago, land separated from African and created Madagascar which is known to be the fourth largest island in the world. This island is called “Great Red Island” because of the prominent red lateritic soils. Lacerites are soil types rich in iron and aluminum, formed in hot and wet tropical areas. Nearly all lateritic are rusty-red because of iron oxides.  These areas are beautiful ranging from coastal beaches to severe grasslands, and raging rivers. One reason the Lemurs are able to flourish in this area is because they are the only primates to inhabit Madagascar. The climate depends greatly on the region. Most Lemurs live in tropical regions but others live in drier areas. The tropical regions have a consistent rain fall and the area is moist most of the year. Other areas have a rainfall from December to April, with drier months from May to November.

Spider Monkey: Known to live in Southern Mexico, the jungles of Central America, and the jungles located in the northern and central regions of South America. They primarily live in the wooded areas rich with high canopy trees. Some Spider Monkeys live off the coast of the Amazon rain forest. These areas have high levels of humidity; they are dense, lush, and high with large amounts of rainfall.

Baboon: Known to live in Africa. They are native to Africa and Asia today. They in habitat a range of environments including tropical rain forest, savannas, shrub land, seashores of Asia, and mountainous terrain. They can be seen on cliff sides off the waters or in trees in the rain forest. Baboons generally prefer savanna and other semi-arid habitats, though they do live in tropical forests.

Gibbon: Known to live in South East Asia; covering ground from China, Burma, North Sumatra, and Malay Peninsula. Gibbons live in the old growth sections of the rainforest much like the other primates mentioned. They spend most of their time in the upper canopies of a lowland rain forest. The upper canopies have tress that reach 60-130 ft tall. This allows for more sunlight. The rainforest in Southeast Asia is known to be the second largest in the world. This region varies, but only slightly, because in the northern region there is mountainous terrain which allows for the climate to be slightly cooler with drier landscapes. The climate in the rain forest of South East Asia is said to be monsoonal which a cause is for drier, warmer seasons.

Chimpanzee: Known to live in western and central Africa. They are rainforest creatures but with most forest dwindling down to nothing, they have scattered from central Africa to the coastal edges. The western side chimpanzees can be found in the savannas; which are a vast, grassy land and treeless. This indicates the chimpanzees are able to adapt to a difference in climate and region if environment demands the migration.

3b) SPECIFIED CHARACTER TRAIT

“The number of teeth of each type is written as a dental formula for one side of the mouth, or quadrant, with the upper and lower teeth shown on separate rows. The number of teeth in a mouth is twice that listed as there are two sides. In each set, incisors (I) are indicated first, canines (C) second, premolars (P) third, and finally molars (M), giving I: C: P: M. So for example, the formula 2.1.2.3 for upper teeth indicates 2 incisors, 1 canine, 2 premolars, and 3 molars on one side of the upper mouth”.

Lemur: Each side of the jaw has two incisors, one canine, three pre-molars, and three molar teeth. The lower incisors are long and narrow. The upper incisors are small. The upper canine are long, broad based, and re-curve. The Lemurs do exhibit sexual dimorphism because the males’ canines are larger than the females. Their dental formula is 2.1.2.3.  The canines are used in combat/fights by slashing the opponents. They are finely spaced and points straight forward in the mouth. The lower incisors and canine teeth are straight forwards and flattened to form a “comb”. This is used to clean or scrap fur. A long, horny filament under the tongue is used to scrape dirt from the teeth. The mandibles move independently because they are not fused. The upper lip is divided and only attaches inside.  The upper lip is attached to the pre-maxilla. This makes it so the Lemur cannot suck; for example, when drinking, they cannot use suction so they have to lap fluids. Lemurs are omnivorous. Lemurs are herbivores. The main diet is of insects. They rely on their moist nose and string sense of smell to locate food.

Spider Monkey: The spider monkey has 36 teeth. They have three pre-molars. They are considered 90% fruigivorous animals because their main dietary focus is of a variety of ripe fruit. Spider monkeys swallow their fruits whole. They also indulge on seeds, nuts, flowers, aerial roots, bird eggs, and honey. Their dental formula is 2.1.3.3. They display high degree of sexual dimorphism with the males having larger teeth than the females.

Baboon: The baboon has 32 teeth. They have two pre-molars. The pre-molar in the mandible is sectional- specialized to sharpen the upper canine teeth. Baboons have a diastema (toothless gap) separating the upper canine from the upper incisors for the lower incisors. Their canines are enlarged and often are mistaken to be “fangs”. Their dental formula is 2.1.2.3. They are partially omnivorous, I say partially because they prefer plants over any other type of food.

Gibbon: They forage for food in the forests hunting for fruits, seeds, leaves, flowers, tree bark, tender plant shoots, insects, spiders, bird eggs, and small birds. From their dietary choices Gibbons are classified as omnivores. Fruit is the main dietary focus but meat from animals counts as 10% of their intake. The Gibbons is an example of an animal that has a unique way of drinking. They drink by dipping a fur hand in the water or by rubbing the hand on wet leaves and then slip the water off the wet fur. Their dental formula is 2.1.2.3.

Chimpanzee: The chimpanzee has 32 teeth (8 teeth x 4 quadrants); with twenty being primary teeth (same as humans). They have two incisors, one canine, two pre-molars, and three molars. Old world apes and humans share this 2.1.2.3 dental formula. The canines are larger, especially larger than humans. Chimpanzees have rounded jaws. They are omnivores and maintain a diet largely consistent with fruits and vegetation. Chimpanzee eats insects including termites, leaves, seeds, tree bark, flowers, and tender plant shoots. They have been known to eat small animals, such as monkeys when they are in groups. They more often than not, drink water by using a chewed leaf as a sponge to sop up the water.

3c) ENVIRONMENTS INFLUENCE ON TRAIT EXPRESSION


The answer to how the dentition trait expresses the influence of the environment may have a simple answer.  There are very little changes seen in evolution in reference to dentition of primates. As already covered, the loss of teeth and the formation of sharper canines and increased incisors is the most profound difference in trait. The trait of this can be demonstrated by the environment our primates reside in. The Lemur is the only primate on the island of Madagascar; hence leaving the need to adapt to more teeth, broader teeth, bigger jaws, and such is not necessary. The environments we see in the primates we studied do not have a need from their environment to change dentition to date. In fact loosing teeth was the need because feeding off of leaves, flowers, small birds, and plants did not constitute the need for more teeth, especially those of the incisors or canines.

3d) IMAGES

baboon

chimp

gibbon

lemur

spider monkey

4) The level of influence the environment has on the dentition patterns is the principal changes in reduction in the number of teeth and an elaboration of the cusp pattern of the molars. As mentioned in my description of traits, I mentioned the dental formula for each primate’s classification.  Because mammalian teeth are specialized for different functions, many mammal groups have lost teeth not needed in their adaptation.” Tooth form has also undergone evolutionary modification as a result of natural selection for specialized feeding or other adaptations. Over time, different mammal groups have evolved distinct dental features, both in the number and type of teeth, and in the shape and size of the chewing surface. “The animals with dentition similar to that of humans are anthropoid apes. These include Chimpanzee, Gibbon, and Gorilla. The shapes of individual teeth in these animals are very close to their counterparts in human mouth. Nevertheless, development of canines, arch form and jaw development are quite different” (drmona.com/detention).

The primitive mammalian formula of 3.1.4.3./3.1.4.3 represents a hypothetical mammalian ancestor with 44 teeth. Whatever the ancestral condition, no living primate has more than three incisors or three premolars on each side in either maxilla or mandible. Prosimians and Platyrrhines have three premolars; Catarrhines have only two. Third molars are often absent in some primate genera. Once a tooth is lost in a species, it is usually not reproduced again. Thus ancestral forms generally may have more teeth, but not fewer teeth of a particular kind than their descendants.
Primitively, eutherian mammals had three incisors in each quadrant (we refer to four quadrants when describing teeth: right side of the upper jaw, left side of the upper jaw, right side of the lower jaw, and left side of the lower jaw), Incisors are usually simple teeth, though the crown is sometimes lobed. In many species, incisors are used as pincers for grasping or picking, both in feeding and in grooming. Primitive eutherians are believed to have had four premolars in each quadrant.
Physical traits such as teeth show a change in the environment for animals. As we noticed, primates lose incisors because those are need for more piercing of meats and alike. Most primates are classified as omnivores (at least the ones we focused on for our study); however, the vast diet is that of plant matter. The increase size in canine teeth is due to adapting to the environments change in the need of survival. Canines are used for defense and attack of an opponent. Thus, canines play an important role in evolutionary change for primates. The teeth are sharper and larger, with the males displaying significant size difference than females. Protection and Prosecution of and from an attacker is essential for reproduction.
In closing I will sum up what is seen as we explore evolutionary dentition changes in primates according to an article…..

 “Common evolutionary trends in the primates: according to Dr. Muna, DrMuna.com/dentition,

I. There was shortening of the jaw due to the decrease in the size of the olfactory organs, upright body position and wide angle of the head to the body.

2. There was decrease in tile tooth size to be accommodated in these jaws, with subsequent elimination of some teeth from the dentition.

3. There was progressive shortening of the arch (in front) and relative widening.

4. Canines reduced in size

5. Lower premolar crowns became more symmetrical from oval.

6. First molars became the dominant cheek teeth.

7. In the upper second and third molars, the dentilingual cusp reduced and often disappeared.

8. Third molars, which were larger than the first molars, were reduced in size and often eliminated”.