The Evolution of Primates

Chapter 22

Learning Objective 1

• What structural adaptations do primates have for life in treetops?

Primates (1)

• Placental mammals • evolved from arboreal shrewlike mammals • Five grasping digits • including opposable thumb or toe

Five Grasping Digits

Hand Foot (a) Lemur (Eulemur mongoz) Fig. 22-1a, p. 467

Hand Foot (b) Tarsier (Tarsius spectrum) Fig. 22-1b, p. 467

Hand Foot (c) Woolly spider monkey (Brachyteles arachnoides) Fig. 22-1c, p. 467

Hand Foot (d) Gorilla (Gorilla gorilla) Fig. 22-1d, p. 467

Primates (2)

• Long, slender limbs • move freely at hips and shoulders • Eyes located in front of head

Learning Objective 2

• What are the three suborders of primates?

• Give representative examples of each

Suborders of Primates

• Prosimii • lemurs, galagos, and lorises • Tarsiiformes • tarsiers • Anthropoidea (anthropoids) • monkeys, apes, and humans

Primate Evolution

Suborder Prosimii Suborder Tarsiiformes Suborder Anthropoidea Hominoids (Anthropoids) Lemurs Tarsiers New World monkeys Old World monkeys Gibbons Orangutans Gorillas Humans Chimpanzees 3 2 1 Common Common anthropoid hominoid ancestor ancestor Common primate ancestor Fig. 22-2, p. 468

KEY CONCEPTS

•

Humans are classified in the order Primates, along with lemurs, tarsiers, monkeys, and apes

•

This classification is based on close evolutionary ties

Learn more about primate evolution by clicking on the figure in ThomsonNOW.

Learning Objective 3

• What is the difference between anthropoids , hominoids , and hominids ?

Anthropoids

• Include monkeys, apes, and humans • Branched into 2 groups: • • New World monkeys Old World monkeys

New World and Old World Monkeys

Hominoids

• Include apes and humans • arose from Old World monkey lineage • 4 modern genera of apes: • • • • gibbons orangutans gorillas chimpanzees

Ape Evolution

(a) Fossils of Aegyptopithecus, a fairly primitive anthropoid, were discovered in Egypt.

(c) Dryopithecus, a more advanced ape, may have been ancestral to modern hominoids.

Fig. 22-5a/c, p. 470

Apes

Fig. 22-6a, p. 471

Fig. 22-6b, p. 471

Fig. 22-6c, p. 471

Fig. 22-6d, p. 471

Hominids

• Humans and their ancestors

KEY CONCEPTS

•

The study of living primates provides clues to help scientists reconstruct the adaptations and lifestyles of early primates, some of which were ancestors of humans

Learning Objective 4

• What are the skeletal and skull differences between apes and hominids ?

Hominid Skeletons

• Adaptations for standing erect and walking on two feet • • • • complex curvature of the spine short, broad pelvis foramen magnum at base of skull first toe aligned with other toes

Gorilla and Human Skeletons

Simply curved spine Foramen magnum at the center rear of skull Foramen magnum at the center base of skull Complex curvature of human spine Tall, narrow pelvis (front view) First toe not aligned with others Gorilla skeleton pelvis (front view) Human skeleton Shorter, broader First toe not opposable, and all toes aligned Fig. 22-7, p. 472

Human Skeleton

• Human skull • • • • • lacks pronounced supraorbital ridge flatter than ape skulls in front has a pronounced chin larger brain than apes jaw structure with teeth arranged in U shape

Human Skull

Supraorbital ridge Incisors Rectangular shape Fig. 22-8a, p. 473

Incisors U-shape Fig. 22-8b, p. 473

KEY CONCEPTS

•

The human brain did not begin to enlarge to its present size and complexity until long after human ancestors had evolved bipedal locomotion

Learn more about monkey, gorilla, and human skeletons by clicking on the figure in ThomsonNOW.

Learning Objective 5

• Describe the following early hominids:

Sahelanthropus, Orrorin, Ardipithecus ramidus ,

and

Australopithecus anamensis, A. afarensis,

and

A. africanus

Sahelanthropus

• Hominid Evolution began in Africa • 6 to 7 million years ago •

Sahelanthropus

• • small brain face and teeth had many characteristics of larger brained human ancestors

Orrorin

• Early hominid • about 6 mya •

Orrorin

• • probably walked upright and was bipedal based on fossil leg bones

Australopithecines (1)

• Include •

Ardipithecus

and

Australopithecus

species •

Australopithecus

species • bipedal (a hominid feature)

Australopithecines (2)

•

Ardipithecus ramidus

• about 5.8 mya to 5.2 mya •

Australopithecus anamensis

•

Australopithecus afarensis

•

Australopithecus africanus

Genus Homo

• Genus

Australopithecus

contains the immediate ancestors of genus

Homo

Possible Evolutionary Relationships

H. sapiens Archaic H. sapiens A. boisei H. erectus A. aethiopicus ?

H. ergaster H. habilis A. africanus H. neanderthalensis A. afarensis A. anamensis A. ramidus Homo Ardipithecus Australopithecus

Fig. 22-9, p. 473

H. sapiens Archaic H. sapiens H. erectus A. boisei A. aethiopicus H. ergaster H. habilis ?

A. africanus H. neanderthalensis A. afarensis A. anamensis A. ramidus Homo Ardipithecus Australopithecus

Stepped Art Fig. 22-9, p. 473

Learning Objective 6

• Distinguish among the following members of genus

Homo : H. habilis, H. ergaster, H. erectus, H. neanderthalensis ,

and

H. sapiens

Homo habilis

• Earliest known hominid with some human features lacking in australopithecines • including slightly larger brain •

H. habilis

fashioned crude tools from stone

Homo erectus

(1)

• Larger brain than

H. habilis

• • made more sophisticated tools may have worn clothing, built fires, lived in caves or shelters

Pronounced supraorbital ridge Receding forehead Projecting face/jaws Fig. 22-10, p. 475

Homo erectus (2)

• Fossils may actually be 2 species •

Homo ergaster

• • earlier African species gave rise to archaic

H. sapiens

•

H. erectus

• • later Asian offshoot may be evolutionary dead end

Archaic Homo sapiens

• Regionally diverse descendants of

H. erectus

or

H. ergaster

• • in Africa, Asia, and Europe about 400,000 to 200,000 years ago • Brains about same size as our brains • • skulls retained some ancestral characters rich and varied cultures

Neandertals

• 230,000 to 30,000 years ago • Short, sturdy builds • • • • receding chins and foreheads heavy supraorbital ridges and jawbones large front teeth nasal cavities with triangular bony projections

Neandertal Tools

Homo sapiens

•

A

natomically modern humans • in Africa about 195,000 years ago • Only members of genus

Homo

remaining • about 30,000 years ago

Cro-Magnons

• Ancient

Homo sapiens

in Europe

KEY CONCEPTS

•

Fossil evidence indicates that the earliest hominids (human ancestors) evolved in Africa and shared many features with their apelike ancestors

Learn more about Homo skulls by clicking on the figure in ThomsonNOW.

Learning Objective 7

• Discuss the origin of modern humans

Origin of Modern Humans (1)

• Out-of-Africa Hypothesis • • • Modern

H. sapiens

arose in Africa migrated to Europe and Asia displaced more primitive humans living there • Supported by recent fossil discoveries and molecular data

Origin of Modern Humans (2)

• Multiregional hypothesis • • Modern humans originated as separately evolving populations of

H. erectus

in Africa, Asia, and Europe Populations occasionally interbred, preventing complete reproductive isolation

KEY CONCEPTS

•

Human culture began when human ancestors started making stone tools

Learning Objective 8

• What is the impact of human culture on the biosphere?

Human Impacts

• Large human brain size • transmission of knowledge from one generation to the next • 2 significant advances in human culture • • development of agriculture Industrial Revolution