To identify crucial features of the evolution of human species, we start by comparing ourselves to our 230 non-human relatives

CHAPTER 6

An Overview of the Primates

Primates

• To identify crucial features of the evolution of human

species, we start by comparing ourselves to our 230

non-human relatives

• 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.

Physical Characteristics of Primates

• Specialized limbs and locomotion

• Lack of dietary specialization, reflected in dentition

• Visual acuity and reduced sense of smell

• Neocortex expansion and greater dependence on

learning

Social Characteristics

• Longer period of gestation and dependency of

offspring

• Dependence on flexible, learned behavior

• Social groups and permanent association of adult

males

• Diurnal activities

Geographical Distribution and Habitats

Primate Habitats

• Most live in tropical or semitropical areas of the new and

old worlds.

• Most are arboreal, living in forest or woodland habitats.

• No nonhuman primate is adapted to a fully terrestrial

environment; all spend some time in the trees.

Primate Diet and Teeth • Omnivorous

• Incisors for biting and cutting; premolars and molars for chewing and grinding

• Dental formula • New World Monkeys have two incisors, one canine, three premolars, and

three molars on each side in both upper and lower jaws: 2.1.3.3. (34 total)

• Old World anthropoids have 2.1.2.3 (32 total)

Primate Limbs

• A tendency towards erect posture.

• Hands and feet possess grasping ability.

• Features of the hands and feet: • 5 digits on hand and feet

• Opposable thumb

• Partially opposable great toe

• Tactile pads enriched with sensory nerve fibers at the ends of digits

Limbs and Evolution

• Many monkeys are able to grasp objects with

an opposable thumb, while others have very

reduced thumbs.

Limbs and Evolution

• Humans are capable of a

“precision grip.”

• Chimpanzees, with their

reduced thumbs, are

also capable of a

precision grip, but they

frequently use a modified

form.

Locomotion

• Quadrupedal, walk on all fours

• Vertical clinging and leaping

• Brachiation

• Knuckle walking

Anatomy, Limb Proportions and Locomotor Patterns

Quadrupedal

• Almost all primates are

at some times

quadrupedal, they walk

on all four legs.

• Apes use specialized

form, knuckle walking,

due to arm length

Quadrupedal

Knuckle walking: Weight is on back of fingers not palms due to arm length

Anatomy, Limb Proportions and Locomotor Patterns

Vertical clinging and leaping.

• Hangs on trees or branches vertically and uses strong hind legs to leap forward or backward.

• Notice long hind legs capable of powerful leaping and shorter front limbs.

• Characteristic of lemurs, and tarsiers

Vertical clinging and leaping

Anatomy, Limb Proportions and Locomotor Patterns

Brachiating • Locomotion by suspending body from one arm and swinging forward and switching to the other arm (think monkey bars) • Semibrachiators also leap and

often use prehensile tail

• All apes are capable of, and occasionally braciate

• Notice arms longer than legs, long curved fingers and shortened thumb, lower back is short and stabilized

• Characteristic of gibbons and siamangs

Brachiating

Primate Senses

• Increased reliance on sight in comparison to other mammals

• Primates have a decreased reliance on the sense of smell.

Vision

• Stereoscopic Vision

• Visual images are superimposed on one another providing depth

perception (three dimensions).

• Stereoscopic vision is partly a function of structures in the brain, visual

input is shared with both hemispheres of the brain.

• Binocular Vision

• Vision characterized by overlapping visual fields provided for by forward-

facing eyes.

• Binocular vision is essential to depth perception

• Color • Color vision is a characteristic of diurnal primates.

• Nocturnal primates lack color vision.

Binocular Vision in Primates

Comparison of Primate Skulls

• The skull of a male baboon compared with that of a red wolf.

• Note the forward-facing eyes above the snout in the baboon, and the lateral position of the eyes of the wolf.

• The baboon’s large muzzle doesn’t reflect a heavy reliance on smell.

Comparison of Primate Skulls

• The skull of a gibbon (left)

compared with that of a

red wolf (right).

• The absolute size of the

braincase in the gibbon is

slightly larger than that of

the wolf, even though the

wolf is six times the size of

the gibbon.

Primate Classification

Survey of Living Primates

• Prosimians

• Lemurs and Lorises

• Tarsiers

• Anthropoids: Monkeys, Apes, and Humans

• New World Monkeys (Platyrrihini)

• Old World Monkeys (Catarrhini)

• Hominoids: Apes and Humans

Lemurs and Lorises

• The most primitive of the primates.

• Characteristics:

• Reliance on olfaction, presence of rhinarium

• Laterally placed eyes

• Shorter gestation and maturation

• Dental specialization called the “dental comb”

Lemur Dental Comb

• Formed by forward-

projecting incisors and

canines.

• This is a derived

characteristic

Rhinarium

• The moist, fleshy pad at the end of the nose seen in most

mammals.

• The rhinarium enhances an animal’s ability to smell.

• This is a primitive (ancestral) characteristic

Lemurs

• Found on the island of Madagascar and other islands off the coast of Africa.

• Extinct elsewhere in the world.

• Characteristics:

• Vertical clingers and leapers with quadrepedialism

• Larger lemurs are diurnal and eat vegetable foods: fruit, leaves, buds, and bark.

• Smaller lemurs are nocturnal and insectivorous (insect -feeding).

Geographical Distribution of

Living Lemurs

Lemurs

Ring-tailed Lemur Sifakas

Aye Aye

Lorises

• Found in tropical forests and woodlands of India, Sri Lanka, southeast Asia, and Africa.

• Characteristics:

• Nocturnal

• Lorises use a climbing quadrupedalism.

• Galagos use clinging and leaping

• Some are insectivorous; others supplement their diet with fruit, leaves, gums, and slugs.

• Females frequently form associations for foraging or in sharing the same sleeping nest.

Slow Loris Slender Loris

Galago or

“Bush Baby”

Lorises

Tarsiers

• Small nocturnal primates found on the islands of southeast Asia.

• Characteristics

• Eat insects and small vertebrates which they catch by leaping from branches (only extant carnivore among the primates).

• Large immobile eyes, 180 degree head rotation

• Basic social pattern appears to be a family unit consisting of a mated pair and their offspring.

Geographical Distribution of Tarsiers

Philippine Tarsier Dian’s Tarsier

Tarsiers

Anthropoids

(Monkeys, Apes and Humans)

• Common traits:

• Larger brain and body size

• Reduced reliance on the sense of smell

• Greater degree of color vision

• Bony plate at the back of the eye socket

• Longer gestation and maturation periods

• Fused mandible

Monkeys

• Represent about 85% of all primate species.

• Divided into two groups separated by geography

and several million years of evolutionary history:

• New World monkeys

• Old World monkeys

New World Monkeys

• 70 species almost exclusively arboreal.

• Found in southern Mexico and Central and South

America.

• Two

• Characteristics:

• Huge variation from tiny marmosets to large howler

monkeys

• Almost all are exclusively arboreal

• All but one are diurnal

Geographical Distribution of

Living New World Monkeys

Marmosets and tamarins

• Eat fruit, leaf buds, insects, and tree sap

• Marmosets and tamarins are unique in that:

• they have claws instead of nails

• bear twins

• live in mated pairs

• males extensively care for their offspring

Golden Lion Tamarin

Pygmy Marmoset

Cebid Monkeys

• Howlers, muiquis, spider monkeys have prehensile tail

used for locomotion and food gathering

• Live in social groups of both sexes and of all ages

Old World Monkeys

• Habitats range from tropical forests to semiarid

desert to snow-covered areas in Japan and

china.

• Characteristics:

• Most quadrupedal and arboreal

• All belong to the Cercopithecidae family.

• Divided into subfamilies, the cercopithecines

and the colobines.

Geographical Distribution of

Living Old World Monkeys

Sexual Dimorphism • Differences in physical characteristics between males and

females of the same species.

• Many old world monkeys and apes display pronounced sexual

dimorphism, this is linked to reproduction strategies

• This will be discussed next week

Orangutan Gelada Baboon Lowland Gorilla

Cercopithecines

• The subfamily of Old World monkeys that includes baboons,

macaques, and guenons.

• Omnivorous: eat fruit, plant matter, insects, small animals and

eggs

• Baboons and guenons are found in Africa

• Macaques are found in southern Asia and India

• Both baboons and macaques live in large social groups of

adults and offspring

Hamadryas Baboon Schmidt’s Guenon

Japanese

Macaque

Colobines

• The subfamily of Old World monkeys that includes the

African colobus monkeys and Asian langurs.

• Primarily leaf eaters

• Live in small groups with one or two adult males

Red Colobus Black and White Colobus Francois’ langur

Hominoids (Apes and Humans)

• Characteristics distinguishing hominoids from monkeys: • Larger body size

• Absence of a tail

• Shortened trunk

• More complex behavior

• More complex brain

• Increased period of infant development

Geographical Distribution of Living Asian Apes

Gibbons and Siamangs

• Found in the tropical areas of southeast Asia.

• Characteristics: • Adaptations for brachiation may be related to feeding while

hanging from branches.

• Diet is largely fruit with leaves, flowers, and insects.

• Basic social unit is a monogamous pair and their offspring with males helping to care for offspring

• Males and females delineate their territories with whoops and “songs”.

White-handed gibbon

• Note the long curved fingers, long arms, and heavily muscled shoulders.

Siamang

• Whooping to mark territory

Orangutans (Pogo pygmaeus)

• Found in heavily forested areas of Borneo and

Sumatra.

• Characteristics:

• Almost completely arboreal.

• Quadrepedal both on the ground and in the trees

• Pronounced sexual dimorphism.

• males = 200 lbs, females = 100 lbs

• Solitary social lives, except mothers with offspring

• Principally frugivorous (fruit-eating).

Orangutans

Female Infant Male

Geographical Distribution

of Living African Apes

Gorillas

• Lowland gorillas are confined to forested areas of

western and eastern equatorial Africa

• Mountain gorillas live in the mountains of central

Africa

• Characteristics:

• Largest of the living primates.

• Males can weigh up to 400 pounds, females 200 pounds.

• Primarily terrestrial, use knuckle –walking.

• Groups consist of one or two large silverback male, a few

adult females, and their sub-adult offspring.

• Vegetarian with some fruit

Western Lowland Gorillas

Male (left) and female with infant (right).

Mountain Gorillas

Female and infant (left) and male (right).

Chimpanzees

• Found in equatorial Africa.

• Characteristics:

• Anatomically similar to gorillas particularly in limb proportions

and upper-body shape.

• Locomotion includes knuckle-walking on the ground and

brachiation in the trees.

• Slightly sexually dimorphic

• Eat a variety of plant and animal foods.

• Large communities of as many as 100 individuals.

• Usually formed around bonded males , but some groups form

around bonded females

Chimpanzees

Male (left) and female and infant (right).

Bonobos (Pan paniscus)

• Only found in an area south of the Zaire River.

• Population is believed to only number a few thousand

individuals.

• Characteristics:

• Less stocky with longer limbs, and less aggressive and more

arboreal than chimpanzees and born with dark face

• Exploit the same foods as chimps, including occasional small

mammals.

• Male-female bonds constitute the societal core.

• Sexuality includes frequent copulations throughout the

female’s estrous cycle.

Female Bonobos With Young

Humans (Homo sapiens)

• The only living species in the family Hominidae.

• Human teeth are typical primate teeth. (2.1.2.3)

• Dependence on vision for orientation to the world

• Flexible limbs and grasping hands

• Omnivorous diet

• Cognitive abilities are the result of dramatic increases in brain size.

• Habitually bipedal

Intelligence

• Mental capacity; ability to learn, reason, or comprehend

and interpret information, facts, relationships, and

meanings.

• The other great apes have been found to have varying levels

• The capacity to solve problems, whether through the

application of previously acquired knowledge or through

insight.

• The other great apes have also shown the ability to problem solve

Endangered Primates

• Over half of all living primates are endangered, many face

immediate extinction.

• Three reasons:

• Habitat destruction

• Hunting for food

• Live capture for export or local trade

Hunting of Primates

• 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.

• Primates are also killed for commercial products.

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