Chapter 6
Overview of the Primates
Overview
•
My favorite line in the whole book: Chimpanzees are not monkeys, but ya gotta love the trunk monkey commercials
•
We study primates because we are a primate species and so by studying those species closest to ourselves we gain
understanding.
o
We use this comparative method to explain physiological and behavioral systems evolved as adaptations.
o
We will look at the primates in a very general sense, but with enough detail that we will see certain patterns emerge.
•
Primatologists are:
o
Scientists who study the evolution, anatomy, and behavior of nonhuman primates.
o
Those who study behavior in free-ranging animals are usually trained as physical anthropologists.
o
The three most famous are Jane Goodall (chimpanzees), Dian Fossey (mountain gorillas), and Biruté Galdikas
(orangutans) -- all protégés of Louis Leakey (famous paleoanthropologist)
•
The primates:
o
There are approximately 230 species of nonhuman primates (lemurs, lorises, tarsiers, monkeys and apes).
o
Each species has come to possess unique qualities for a particular habitat and lifestyle.
o
Contemporary primates (including humans) aren’t necessarily a representation of the final stage of a lineage.

Living primates are not “better” than their evolutionary predecessors or other living species.

Each possesses unique qualities that make it better suited to a particular habitat and lifestyle.
Primate Characteristics 1
•
First primates are placental mammals (infraclass called Eutheria) so that they exhibit these traits: body hair, relatively long
gestation period, live birth, mammary glands, heterodont (different types of teeth), constant body temperature
(endothermy), and a strong capacity to learn, thus behavioral flexibility
•
Further, we are part of the order called Primates. So what traits distinguish the primates from other mammals?
o
Because primates are not especially specialized, there are not a few traits that define the order. So there is a group of
traits anthropologists use.
o
But it is a generalized list (not every primate has every trait).
o
This is a good time to mention that you need to know the terms for types of traits that were introduced in Chapter 5:
generalized, specialized, primitive (ancestral), derived, shared, and unique.
•
List of primate characteristics (physical)
o
Limbs and locomotion

Tendency to erect posture based on a flexible, generalized skeleton

Hands and feet with a high level of prehensibility (ability to grasp); not all primates have highly efficient opposable
thumbs

Tactile pads and nails on fingers and toes

Hands are adapted for precision grip and well as power grip and the retention of 5 digits on hands and feet.

Nails, not claws (generally, but some New World monkeys do not and all prosimians have 1 claw on one digit).
Primate Characteristics 2
•
List of primate characteristics (physical) (continued)
o
Diet and teeth

Lack of dietary specialization, means most are omnivorous

Terms: Omnivore (means ‘all eating’); carnivores (including insectivores); herbivores (which include frugivores
(fruit-eaters) and foliovores (leaf-eaters).
o
Teeth are generalized because primates are omnivorous
•
One way to describe the heterodont pattern of primates is by the dental formula.
o
This is the number of each kind of teeth on the upper mouth (one side) with the number of each kind of teeth on the
lower mouth (one side)

Kinds of teeth: incisors, canines, premolars, and molars. Dental formula is largely consistent with that of other
mammals

Not all primates have the human dental formula
o
Notice the gap for the New World monkeys? That is called a diastema and is so the upper canine can fit in many
primates)
Primate Characteristics 3
•
List of primate characteristics (physical) (continued more)
o
The senses and the brain

Nocturnal (night-active) primates are more likely to rely more on the sense of smell
(olfactory sense) than diurnal (day-active) primates, which rely more on the sense of
vision.

Color vision is a characteristic of all diurnal primates. The nocturnal owl monkey
only sees monochromatically. In between these extremes, color vision is variable.

Depth perception (stereoscopic vision) allows primates to see 3-D. Several
mechanisms help this to happen:
•
Binocular vision (two eyes in front that have overlapping visual fields)
•
Visual information is transmitted to both sides of the brain (60 opposite side of
brain-40% on same side).
•
3-D images are produced by specialize d structures in the brain.

Decreased olfaction (see Figure 6-4 and look for position of the eye sockets and the
postorbital bar)

Expansion and increased complexity of the brain
•
Primates have the highest brain to body ratio
•
The expansions are especially in the areas of the neocortex (where different
sensory modalities are processed)
1.
2.
3.
Center your nose over the eye
Focus your eyes on the eye.
Put your free thumb in front of your
nose.
4.
Continue to focus on the eye. If
both eyes are on, you will see two
thumbs framing one eye.
5.
Now, switch your focus to your
thumb. You should see two eyes
framing one thumb.
Source: The framing game
Primate Characteristics 4

List of primate characteristics (social)
o
All primates are social. Even those that live alone successfully
can group together if resources allow (for instance orangutans)
o
Maturation, learning, and behavior

Primates are K-selected species as their reproductive
strategy; basically this requires:
•
More efficient fetal nourishment
•
Longer periods of gestation
•
Reduced number of offspring
•
Delayed maturation
•
Extension of life span
•
Less widely distributed to reduce loss of offspring in novel environments.

The other option a species can use is to be a r-selected species in term of one’s reproductive strategy.
•
Take the list above and think the opposite.
•
If curious, you might watch Nova: Rat attack
o
Greater dependency on flexible, learned behavior
o
Tendency to live in social groups
o
Tendency to diurnal activity patterns (of course some prosimians and one monkey species are nocturnal)
Primate Adaptations 1
•
It is important that we understand the physical and social characteristics of primates as adaptations to environmental
circumstances.
o
The traditional explanation was based on the observation that primates are arboreal and so this is called the arboreal
hypothesis which is the idea that:

These traits appear to be for the adaptive niche that is arboreal

In other words, primates adapted to living in the trees, while other mammals were ground dwellers.

This explains the reliance on vision in the 3-D world of the trees, the omnivorous diet (eat leaves fruits, nuts,
insects, small mammals) and depth perception.
o
A more recent hypothesis is called the visual predation hypothesis which says that:

The forward face of primates is found in all predators

Also suggests that the grasping hands and feet and the presence of nails may be an adaptation to shrubby forest
undergrowth and lowest forest tiers where proto-primates say insects and small prey
o
Mixed diet hypothesis is a third hypothesis and suggests:

Primates adapted to angiosperms (flowering plants) which appeared about 140 mya
115_Chapter 6 Page 2
States that these same traits make for better eating of small food items such as fruits, berries and seeds located
among branches and on stems.
These hypotheses are not mutually exclusive.

•
Primate Adaptations 2
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Geographical distribution and habitats
o
Most modern primates are found in semi-tropical or tropical environments. Geographic regions include southern
Mexico, Central and South America, Africa, India, Southeast Asia (many islands, too) and Japan
•
Environments
o
Most live in arboreal environments and in woodland or forest habitats
o
Exceptions to these rules include:

Baboons, macaques and humans have wide-ranging distributions

Some have voluntarily moved, others relocated as part of research.
Primate Adaptations 3
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Locomotion
o
Generalizations:

All primates are, to some degree, quadrupedal (use all 4 limbs for locomotion)

All primates are bipedal to some degree (use lower limbs for locomotion)
o
Quadrupedal types of locomotion:

Terrestrial quadrupedalism (walking on all 4 limbs as adapted to the ground) (Common in some lemurs, baboons,
and macaques)

Arboreal quadrupedalism (walking on all 4 limbs as adapted to the trees)
o
Knuckle-walking is a type quadrupedalism where the weight of the upper body is supported by the knuckles, not the
palms
o
Vertical clinging and leaping is seen in many prosimians and tarsiers. Extra long lower limbs provide the push and
adaptations of the limbs provide the ‘stick’
o
Brachiation (arm swinging) requires greater upper limb length to lower limb, long, curved fingers, reduced thumb size,
& a short, stable back.

The best primate true brachiator is the gibbon.

Semi-brachiation (although it is not true brachiation) is found in some New World monkeys which are assisted in
their arm swinging by use of a prehensile tail
Primate Classification
•
Your book tends to merge two different taxonomies together so this necessitates introducing both the tradition taxonomy
and the revised taxonomy.
o
The traditional taxonomy puts the tarsiers in with the lorises and lemurs. The alternative taxonomy puts the tarsiers in
with the New World monkeys (NWM), Old World monkeys (OWM), the apes and humans.
o
The alternative taxonomy is more accurate, based on fossil evidence.
•
Traditional taxonomy
o
The 2 suborders of primates (prosimians and anthropoids) represent the traditional classification system.
o
In the traditional taxonomy the suborder Prosimi (prosimians) include lemurs, lorises, and tarsiers.
o
In the traditional taxonomy the suborder Anthropoidea (anthropoids) are monkeys, apes, and humans.
•
Alternative taxonomy
o
Biochemically and genetically, the tarsiers are not prosimians, but they do represent a mixture of anatomical traits of
the prosimians and the anthropoids.
o
If one moves the tarsiers in with the anthropoids, this new taxonomic group is called the suborder Haplorhini
(haplorhines) for their dry noses and the combination of lemurs and lorises is called the suborder Strepsirhini
(strepsirhines) for their wet noses.
Traditional Classification of Primates
Alternative Classification of Primates
115_Chapter 6 Page 3
A Survey of the Living Primates 1
•
This survey of the primates is extremely general. Remember there are about 230 living species.
o
The intent, then, is to give a glimpse concerning the diversity of the order Primates.
o
As we proceed, try to note where the authors shift between the 2 taxonomic systems
•
Lemurs and lorises
o
Lemurs and lorises retain more of the primitive primate traits,

Includes a stronger reliance on olfaction.
•
One example of this reliance on olfaction is the presence of a rhinarium
•
Another example is that there is a more lateral placement of the eyes

Another primitive trait is a shorter gestation and maturation

They also posses dental specialization called the dental comb. This dental comb is used in grooming and feeding

They have a claw on the second toe.

Their faces are less mobile (‘poker-faced’)

Tapetum lucidum or a layer of cells in the eyes of some animals that increases the reflection of light on the retina.

Postorbital bar is not closed.
A Survey of the Living Primates 2
•
Profile of the lemurs
o
Geography/habitat

Lemurs are found only on the island of Madagascar and nearby islands off the east coast of Africa; extinct
elsewhere in the world

Lemurs diversified into ecological niches without competition and number about 60 species today. Some are
arboreal, others (including the ring-tailed lemur) are terrestrial.

Some arboreal species are quadrupeds and others are vertical clingers and leapers (sifakas and indris)

Physical traits
•
Lemurs range in size from the small mouse lemur, with a body length of only 5 inches, to the indri, with a
body length of 2 to 3 feet.
•
Larger lemurs are diurnal and are comparatively omnivorous; The smaller lemurs are nocturnal and
insectivorous.
o
Social behaviors

Some are socially gregarious (ring-tailed lemurs and sifakas) live in groups of 10-25 animals

Others (the indris) live in family units of mated pairs and offspring

Several nocturnal forms are mostly solitary.
A Survey of the Living Primates 3
•
Profile of the lorises
o
Lorises were able to survive in mainland areas of Africa by adopting to nocturnal activity.

Where are they?
•
There are at least eight loris species found in tropical forest and woodland habitats of India, Sri Lanka,
Southeast Asia, and Africa.
•
An additional 6-9 species of galagos (bush babies) are found in the forested/woodland areas of sub-Saharan
Africa

Locomotion is by slow, cautious climbing of quadrapedialism for the lorises, but the galagos are agile vertical
clingers and leapers.

Some lorises and galagos are almost completely insectivorous, Others supplement the diet with fruit, leaves, gums
and slugs.
115_Chapter 6 Page 4
•

Foraging is mostly solitary (females leave infants behind) but ranges may overlap.
Profile of tarsiers
o
There are five recognized tarsier species all in island areas in Southeast Asia.

Tarsiers are nocturnal insectivores that leap onto prey from lower branches and shrubs.

They appear to form stable pair bonds, and the basic social unit is a mated pair and their young offspring.

Tarsiers have only two, rather than four, incisors in their lower jaw. Their dental formula is 2.1.3.3/1.1.3.3
A Survey of the Living Primates 4
•
Profile of tarsiers (continued)
o
Tarsiers are a blend of characteristics.

Prosimian traits include: nocturnal activity, small body size, unfused mandible (lower jaw), relatively large ears,
and a grooming claw.

Anthropoid traits include: lack of naked rhinarium (dry nosed), enclosed bony eye sockets, chromosomal/DNA
arrangements and internal arrangements match those of other anthropoids.
•
In tarsiers, the internal structures of the nose and ears and the blood supply to the brain and to a developing
fetus are more like those of monkeys than of lorises.
•
The monthly sexual swellings of female tarsiers are also similar to those in anthropoids

Unique traits include: large eyes - each is larger than their brain, and they are immobile in their sockets. neck capable of rotation up to 180 degrees. (Tarsiers are primarily insectivores and this eye/neck combination may be
helpful in catching their prey at night.)
Source: PrimatePage (2004).Tarsier. Retrieved from http://www.geocities.com/RainForest/Canopy/3220/IOtarsiiformes.html
Source: Ijsselstein. (2004, April 24). The Philippine tarsier. Retrieved from http://www.bohol.ph/article15.html
A Survey of the Living Primates 5
•
Anthropoids: monkeys, apes & humans
o
General statements, but here are a few points to keep in mind:

Monkeys and apes are often confused in the popular imagination. Monkeys have tails. Apes and humans do not.

Monkeys generally have smaller brains relative to body size that apes or humans.

Monkeys are quadrupedal (all four legs are of equal size and make contact with the ground). Apes have relatively
longer arms than legs; humans have longer legs than arms
•
Features of the anthropoids
o
Generally larger body size and a larger brain
o
Reduced reliance on sense of smell and an increased reliance on vision.
o
Greater degree of color vision with the back of eye socket formed by a bony plate
o
Blood supply to brain different from prosimians
o
Fusion of two sides of the mandible to form one bone.
o
Less-specialized dentition
o
Different female internal reproductive anatomy and longer gestation and maturation periods
o
Increased parental care and more mutual grooming
A Survey of the Living Primates 6
•
Profile of the New World Monkeys (NWM)
o
The New World moneys are the only form of anthropoids found native to the New World (Mexico and Central and
South America) and there are about 70 species

They share many similarities to Old World monkeys, but separate lines of evolution are reflected in several
important differences

They exhibit a wide range of size, diet and ecological adaptation
•
Size ranges from 12 ounces (tiny tamarins and marmosets) to 20-pound howler monkey
•
Almost exclusively arboreal, and some species never come to the ground
•
Mostly found in forested region
•
Only the owl monkey is nocturnal, all others are diurnal
•
Traditional taxonomy is Callitrichidae and Cebidae Today it is disputed, but we will use for now
o
Callitrichidae are the marmosets and tamarins

These are the smallest

Claws instead of nails, which they use to climb

Mostly insectivores, but the marmosets also eat gums
115_Chapter 6 Page 5

Small groups of mated pair or 1 female and 2 males and their offspring (tamarins may have twins)
A Survey of the Living Primates 7
•
Profile of the New World Monkeys (NWM) (continued)
o
Cebidae are all others

Range in size from squirrel monkey (12 inches) to howler (24 inches)

Varied diet with combinations of fruit, leaves with some insects

Most are quadrupedal, with a few semibrachiators (muriquis, howlers, and spider monkeys) The prehensile tail of
New World monkeys is a derived trait. The Howler monkey is an example of a New World monkey.

Socially in groups of both sexes and ages, Some are monogamous pars with subadult offspring (titis)
•
Profile of the Old World Monkeys (OWM)
o
Except for humans, the Old World monkeys are the most widely distributed primates and are found in sub-Saharan
Africa, southern Asia and even Japan.
o
OWM are both biochemically and physically more similar to humans than are New World monkeys.

They share the same 2.1.2.3/2.1.2.3 dental formula has occupy a wide range of environments, including tropical
rain forests and savannas (open grasslands).

Most Old World monkeys are quadruped (moving on all fours) and arboreal, but some are adapted to a terrestrial
life (baboons).
A Survey of the Living Primates 8
•
Profile of the Old World Monkeys (OWM) (continued)
o
The group Cercopithecidae are divided into two subfamilies

The cercopithecines are the more generalized of the two subfamilies, are more omnivorous, using cheek pouches to
store food

Most are found in Africa, but the macaques are in Asia, India and Japan

The species of the subfamily colobine are narrower in food preferences and mainly eat mostly leaves
•
Called foliovores, also called the leaf-eating monkeys
•
Mostly found in Africa, but the red colobus and the white colobus are found in Africa
o
OWM are very sexually dimorphic, especially the baboon and the patas (males as large s 80 pounds, females about
half)

In some species (especially baboons and macaques)

Females in estrus have pronounced external genitalia when in estrus
o
Socially (complicated, but generally):

The colobines tend to live in small groups of 1-2 adult males

Savannah baboons and macaques are in large social units

Monogamous paring is not common in OWM, but is seen in a few langurs and maybe 2 of the guenon species
A Survey of the Living Primates 9
•
Hominoids (Apes and Humans)
o
Apes and humans differ from monkeys in several ways:

Larger body size (except for gibbons and siamangs), along
with absence of a tail

Shortened trunk as well as differences in the shoulder joint

More complex behavior, along with more complex brain and
enhanced cognitive abilities
Source: Wikicommons

Increased period of infant development and dependency.
o
The superfamily Hominoidea includes;

Small gibbons and siamangs in the family Hylobatidae

Some great apes in the family Pongidae (orangutans, gorillas,

New taxonomy puts other great apes (bonobos, and chimpanzees)in same tribe as humans (Hominin). At the
subtribe level (not pictured) they break out into Hominina and Panina
A Survey of the Living Primates 10
Profile of gibbons and siamangs
o
Gibbons and siamangs are the members of the family Hylobatidae
•
115_Chapter 6 Page 6
o
o
o
o
o
o
o
o
These 12 or so species live in the southeastern tropical regions of Asia (Number is debated because of taxonomic
disagreements)
The gibbon and siamangs are the smallest of the living apes. Body size is about 13 pounds for gibbons and 25 pounds
for siamangs
They usually live 80-100 feet up in the trees.

Both are adapted for brachiation.

They can feed while suspended

They eat a variety of leaves, flowers and insects

Can travel 3 meters in one swing up to 10 meters!
Walk using bipedal locomotion if on the ground
They have a monogamous family structure (adult male, adult female and offspring).
Sometimes called ‘monogamous’ but have been seen to mate with others outside the bond.
Males are very involved in child rearing
They actively defend territories. The range can be up to 50 acres. Vocalizations are a part of this protection of range
A Survey of the Living Primates 11
•
Profile of orangutans
o
The word orangutan means “man of the forest” in Malay. Its most obvious physical characteristic is its reddish brown
hair. Orangutans are called the ‘red apes’.
o
The orangutan is a large ape found only in certain areas of Southeast Asia (Sumatra and Borneo).
o
Can reach 200 pounds for males, females about 100 pounds (sexually dimorphic)
o
Orangutans are agile climbers and hangers and are largely arboreal.

They slowly rock the tree they are on in the direction of the next and move over when they are close together.

Bipedal on the ground
o
Orangutans tend to be solitary.

Their primary social group consists of mother & infant.
•
Males are not needed for protection.
•
There is little danger of predation.

Offspring may stay with mother as long as 8 years. Critical in a species that is mostly solitary to learn as much as is
possible.
o
They are polygamous, with the males home range overlapping a number of females’ home ranges
o
Small group size may reflect an environment with widely scattered food resources
A Survey of the Living Primates 12
•
Profile of gorillas
o
The gorilla is the largest living primate.

They are found only in equatorial Africa.

Three subspecies are described by location:
•
Western lowland gorillas in west and central Africa is the most numerous (book reports 110,000, but in 2008
found another 125,000!)
•
Eastern lowland gorillas are fond in the Congo at 12,000
•
Mountain gorillas are found in Rwanda, the Congo, and Uganda at 600

They are predominantly terrestrial and are knuckle-walkers (walk on all fours with the weight of the arms resting
on the knuckles of the hands).

Because of their size, gorillas have few problems with predators (except for armed humans). Poaching and
encroachment by humans has caused their range to rapidly disappear The adult silverback is dominant and can
reach 400 pounds, females 200

Mountain gorillas live in small social groups of an adult male, several adult females, and their immature offspring.
Blackback males, who may be tolerated by the silverback, are likely his sons.

Western lowland gorillas are understudied, but may be socially similar to the mountain gorillas
o
Almost exclusively vegetarian Seen using a long stick to dig
o
Despite many myths concerning their desire for human flesh, they eat a diet of primarily leaves and fruit. Gentle unless
threatened.
A Survey of the Living Primates 13
•
Profile of chimpanzees
115_Chapter 6 Page 7
o
o
o
o
o
o
o
Chimpanzees are probably the best known of primates.
Found in equatorial Africa, but also in laboratory settings
Anatomically similar to gorillas, but some differences as they spend more time in the trees. Younger chimps may
brachiate in the trees, but knuckle-walking is most common form of locomotion
Males may reach 150 pounds, females 100 pounds, so there is sexual dimorphism, but less than seen in orangutans or
gorillas.
Very omnivorous

Known to fish for termites or use rocks to crack nuts

Know to hunt in groups (males)

Now know can make spears to hunt bush babies
Social groups are very fluid (fission-fusion), volatile, and made of bonded males

Tend to forage alone or in small groups

Adult males are generally dominant.
Females in estrus may leave own group temporarily or permanently
o
The most important social behaviors revolve around mother and infant.
A Survey of the Living Primates 14
•
Profile of bonobos
o
Bonobos are the least well known of the African apes.

They are closely related to the chimpanzee, and were commonly considered a separate species of chimpanzee
known as “pygmy chimpanzee.”

They are slightly smaller, have a more linear body build, longer legs to arm ration, a smaller head, dark face from
birth, and tuffs of hair at side of face.

They can walk upright more easily than other apes and are more arboreal than chimpanzees
o
It has been suggested that the first hominoids may have been quite similar in many ways.
o
They are unique to a restricted rainforest region of Zaire, central Africa. There is no accurate count of bonobos.
Estimated to be between 10-20,000
o
They eat a leaf and plant diet

Includes worms and fish

Some examples of hunting monkeys
o
Social structure

Seem to be less violent than chimpanzees; Franz de Waal (well-known primatologist) calls them “hippies” for their
peaceful, sex-focused behaviors

Bonobos live in large multimale / multifemale groups like chimpanzees and also practice fission-fusion during the
day and regroup at night.

The social bond is female core: Strongest social bonds exist between adult females, even though they are not
related (females leave natal group around 8 years of age).
•
Female-male bonds are stronger than seen in chimpanzees. Strongest social bonds exist between adult females.
•
Females may have first baby at about 13 years and may carry an infant for up to 2 years after birth
A Survey of the Living Primates 15
•
Profile of humans
o
Human beings are basically exaggerated African apes.
o
The closeness is poignantly pictured here
o
We are unique (among mammals) in our form of habitual bipedal locomotion.
o
We are adapted to digest a wide assortment of foods
o
Except for reduced canine size, human teeth are typical primate teeth.
o
Dependence on vision, decreased reliance on olfaction, flexible limbs and grasping hands, are rooted in our primate
past.
o
The neurological basis for intelligence is something we share with other primates Defined as:

Mental capacity; ability to learn, reason, or comprehend and interpret information, facts, relationships, and
meanings.

The capacity to solve problems, whether through the application of previously acquired knowledge or through
insight.
115_Chapter 6 Page 8
o
o
There are many kinds of intelligence (others argue these are abilities): Linguistic intelligence, logical-mathematical
intelligence, musical intelligence, spatial intelligence, bodily kinesthetic intelligence, interpersonal intelligence, and
intrapersonal intelligence
Human are completely dependent on culture. Which explains the human paradox (How can a K-selected species like
humans be so widely distributed geographically?)
Endangered Primates
•
Three reasons for the worldwide depletion of nonhuman primates
1.
Habitat destruction
2.
Hunting for food (bushmeat)

In West Africa the most serious problem is hunting to feed the growing human population.

Estimated that thousands of primates, are killed and sold for meat every year.
3.
Primates are also killed for commercial products. Live capture for export or local trade
•
Why primates make bad pets
o
They are too smart to be pets
o
They are aggressive and not domesticated
o
They are endangered; one estimate is that 4 primates die for each that is sold
o
They live a long time (some species nearly as long as humans)
o
They are social so having a single pet makes them insane (literally)
•
Like primates? Support sanctuaries
o
Here is one called Born Free Primate Sanctuary
o
Here is another called OPR Coastal Primate Sanctuary in Washington
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