The Living Primates

Example One

List some key traits of Prosimians vs. Anthropoids. Focus on a few key differences. Discuss them in terms of primate evolution.

Primates are divided into two large categories: Prosimians and Anthropoids. Prosimians are the earliest primates and are comprised of lemurs, lorises and tarsiers. Anthropoids are comprised of monkeys, apes and humans. Prosimians and Anthropoids each have their own unique differences which are explained below.

Three distinct physical features associated with Prosimians are their teeth, extremities (legs and arms) and eye positioning. As Wendy Birky PhD explained in the video lesson, many Prosimians have a “dental comb” which is comprised of the incisors on the lower jaw that point outward nearly to the point of being positioned horizontal to the jaw. The front teeth may also be used for grooming. Prosimians also have long legs and shorter arms for vertical clinging and leaping. Anthropologist Naomi Bishop stated the structure of the legs is an adaptation for life in the forest, thus allowing for locomotion by pushing off with hind legs. The eyes of Prosimians are off to the side of the head which provides for less developed stereoscopic vision.

The sense of smell is prominent in some Prosimians which depend on smell more than monkeys and apes. Many Prosimians have a moist nose and long mussel to guide odors to the brain. The sense of smell is important for the lemurs because it is used as a communication method to mark territory or during mating season. The behavioral trait of Prosimians are predominantly diurnal which is defined as active during daylight hours, however a few are nocturnal or active at night as well.

In contrast, Anthropoids are larger than Prosimians and have larger brains relative to body size. Whereas Prosimians rely on the sense of smell, Anthropoids depend more on sight. Anthropoids have a boney eye socket, color vision and eyes that are positioned on the front of the skull versus on the side. The offspring of Anthropoids are slower to mature and have a longer dependency on their mother and social groups. In comparison, Prosimians can mature to adulthood in only 20 months and are less dependent on their mother.

When examining these traits in terms of primate evolution, these characteristics developed in response to environmental pressures. For example, the tropical and sub-tropical climates impacted the environment primates evolved in. Primates live primarily where the climate is warm. Over time the early primates became less dependent on smell and increased importance on vision as the Anthropoids evolved. Brain size also increased with the Anthropoids and eyes became positioned on the front of the face.

Vocabulary:

*primates – include humans, prosimians, monkeys and apes; share a grasping hand and foot, nails instead of claws; eyes on front of the face with overlapping visual fields; dependency on vision; larger brain; young that mature slowly.

*arboreal – life in the tree; shaped the form and behavior of all the primates

*stereoscopic vision – eyes that face forward

*morphology – physical characteristics of each primate example: the 5 fingers and toes, hair tell us they are mammals; grasping hand and thumb; lack of a tail characteristics of all apes and humans

*adaptive niche – where a primate spends its time; what they eat and what they need from their environment; a result of specific environmental pressures

*Diurnal - Active during the day – majority of species are diurnal; eyes not as large

*nocturnal – active at night

*New World Monkeys – live in Central and South America; an Anthropoid; exclusively arboreal; diurnal

*Old World Monkeys – live in Africa and Asia; an Anthropoid; diurnal; quadrupedal locomotion

*quadrupedal – move and jump on all four feet; front and hind limbs of almost equal length

*omnivorous – monkeys that eat a large variety of plant and some animal foods, eggs, insects but mostly leaves and fruit

*sexual dimorphism – difference in size, shape and color between the sexes; males can be twice as large as females

*brachiation – uses rotating shoulder to suspend the body - arm hanging and arm swinging; requires a strong stable longer arms to swing; shoulder blades that sit on the back of the body instead of the side;

Example Two

a. List some key traits of Prosimians vs. Anthropoids. Focus on a few key differences. Discuss them in terms of primate evolution.

As discussed in the DVD, Prosimians are the closest living examples we have of the features of the earliest primates. The prosimian radiation occurred between 33 million and 55 million years ago, and a wide variety of prosimian forms emerged at that time. Modern prosimians depend more on smell than monkeys and apes do, which is evident in their moist nose and long muzzle containing a honeycomb of bone that helps to guide odors to the brain. Their eyes tend to be more off to the side with less developed stereoscopic vision. They reproduce more rapidly than anthropoids do. In a number of species, young can mature to adulthood in only twenty months. Many have one or more claws that they use for extracting food or grooming, since they lack the ability to oppose their thumbs and fingers in a precision grip. Some also use their front teeth to groom themselves and others. [Yoana, is this excerpted from the book? If so, we always have to give credit.] As stated by Wendy Birky (Anthropologist – commentator), “One feature that many prosimians share is the presence of a dental comb – the incisors on the lower jaw are pointing outward, almost horizontal to the jaw.” Prosimians tend to have long legs and short arms a morphology evolved for a form of locomotion called vertical clinging and leaping. Per Naomi Bishop, “A vertical climber and leaper sits straight upright on a tree trunk and clings to the tree trunk and pushes off with the hind legs to another tree trunk. It’s basically an adaptation for life in the forest at a level in the canopy where there isn’t any canopy. You’re not running from branch to branch, you’re jumping from trunk to trunk. Prosimian limb proportions give animals a hunched look on the ground. [When your post gets long, please paragraph it, like this here. OK?]

Prosimians can be divided into three groups; lemurs, lorises, and tarsiers. Lemurs are only found in the island of Madagascar. Isolated there with no primate competitors, they diversified into many different species. The majority of these species are diurnal, while some are nocturnal. Many lemurs communicate extensively through smell. Lorises live in Africa and Asia. In these continental areas, they have competition from many diurnal monkeys and apes. Because of this, all loris species today are nocturnal creatures. They use their large moveable ears to locate insects and prey. Tarsiers live in Southeast Asia. These tiny primates got their name from their elongated tarsal (ankle) bone that enables these 3-6 inch tall primates to jump distances of nine feet. Tarsiers are closely related to anthropoids and among the most important characteristic that they share is the absence of a wet nosed snout. Lemurs and lorises are our contemporaries, not our ancestors.

Anthropoids include monkeys, apes, and humans. As explained in the DVD, they tend to be larger than prosimians. They also have larger brains relative to body size than prosimians do. They depend on sight more than smell, with a bony eye socket and color vision. Their nose is not moist and is separated from the mouth by an upper lip. Anthropoids are slower to mature with a longer period of dependency on the mother and social group. As a result, their behavior is shaped by learning to a much greater extent. Eighty-five percent of all living primates are monkeys. Monkeys can be found on four continents occupying all types of forest, grassland, mountains and even urban areas. Morphologically, monkeys are quadrupedal. Whether in trees or on the ground they run and jump along horizontal surfaces. During new world monkeys’ separate evolution, one group evolved a grasping tail that could be used as a fifth arm, allowing them to hang suspended underneath branches, giving them access to a much larger radius of available food in the branches of trees. The tail is also used in locomotion and to stabilize these large monkeys high in the tree tops. New world monkeys can be easily distinguished by [<-- from?] their old world counterparts by the presence of widely separated nostrils. They range from small bodied species, like squirrel monkeys, to large slow howler monkeys. Old world monkeys are the most widely dispersed primates, except for humans. They are found in habitats as diverse as tropical rainforests, savannah grasslands, cities, the high Himalayas, and the mangrove swamps of Southeast Asia, where they swim and eat shellfish. They are group-living, diurnal and mainly arboreal.

N.B. Ok, so what is the source for the foregoing set of information, Yoana? If it's gathered from some source (other than Yoana), then it must be accounted for. Citations and/or summaries must always be documented. This does not mean that your information is incorrect; it does, however, mean that it need to be referenced. Finally, where are your references to the specialists in the lesson?

Primates – a diverse group, including humans, share a grasping hand and foot with nails instead of claws, eyes that sit on the front of the face with overlapping visual fields, and increased dependence on vision, a generalized dentition, a larger brain for their body size, and young who mature slowly. Earlier species show only the beginnings of some of these characteristics, while the later evolving apes and humans demonstrate all of them.

Arboreal – living in trees; life in the trees that shaped the form and behavior of all the primates.

Stereoscopic vision – enabled by eyes that face forward with overlap in the visual field; useful to the early primates in their arboreal habitat; enables a mammal to see in 3D to be able to judge distances very well.

Adaptive niche - The behavior and morphology of each living primate species today also reflects the habitat they occupy. Where a species spends its time, what they eat, and what they need from their environment; the result of specific environmental pressures, and so a species may behave differently in different habitats.

Diurnal – to be active during the day

Nocturnal – to be active at night

New world monkeys – live in central and south America; exclusively arboreal and all but one are diurnal

Old world monkeys – live in Africa and Asia

Quadrupedal – to move and jump on all four feet with front and hind limbs of equal length

Sexual dimorphism – distinct difference in size or appearance between the sexes of an animal in addition to difference between the sexual organs themselves.

Brachiation – upper body anatomy that allows apes to hang and swing by their arms under branches; requires a short immobile trunk, a strong stable shoulder joint, and longer arms relative to legs.