The Evolution of Primates Chapter 22

Learning Objective 1 What structural adaptations do primates have for life in treetops?

Primates (1) Placental mammals Five grasping digits evolved from arboreal shrewlike mammals Five grasping digits including opposable thumb or toe

Five Grasping Digits

(a) Lemur (Eulemur mongoz) Hand Foot Figure 22.1: Right hands and feet of selected primates. (Figures not drawn to scale.) (Adapted from A. H. Schultz, The Life of Primates, Weidenfeld & Nicholson, London, 1969.) (a) Lemur (Eulemur mongoz) Fig. 22-1a, p. 467

(b) Tarsier (Tarsius spectrum) Hand Foot Figure 22.1: Right hands and feet of selected primates. (Figures not drawn to scale.) (Adapted from A. H. Schultz, The Life of Primates, Weidenfeld & Nicholson, London, 1969.) (b) Tarsier (Tarsius spectrum) Fig. 22-1b, p. 467

(c) Woolly spider monkey (Brachyteles arachnoides) Hand Foot Figure 22.1: Right hands and feet of selected primates. (Figures not drawn to scale.) (Adapted from A. H. Schultz, The Life of Primates, Weidenfeld & Nicholson, London, 1969.) (c) Woolly spider monkey (Brachyteles arachnoides) Fig. 22-1c, p. 467

(d) Gorilla (Gorilla gorilla) Hand Foot Figure 22.1: Right hands and feet of selected primates. (Figures not drawn to scale.) (Adapted from A. H. Schultz, The Life of Primates, Weidenfeld & Nicholson, London, 1969.) (d) Gorilla (Gorilla gorilla) Fig. 22-1d, p. 467

Primates (2) Long, slender limbs Eyes located in front of head 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 Tarsiiformes Anthropoidea (anthropoids) lemurs, galagos, and lorises Tarsiiformes tarsiers Anthropoidea (anthropoids) monkeys, apes, and humans

Primate Evolution

Suborder Tarsiiformes Common primate ancestor Suborder Prosimii Suborder Tarsiiformes Suborder Anthropoidea Hominoids (Anthropoids) Gorillas Humans Gibbons New World monkeys Old World monkeys Lemurs Tarsiers Orangutans Chimpanzees 3 2 1 Figure 22.2: Primate evolution. This branching diagram, called a cladogram, shows evolutionary relationships among living primates, based on current scientific evidence. The nodes (circles) represent branch points where a species splits into two or more lineages. ●1 The divergence of orangutans from the ape/hominid line occurred some 12 mya to 16 mya. ●2 Gorillas separated from the chimpanzee/hominid line an estimated 8 mya, and ●3 the hominid (human) lineage diverged from that of chimpanzees about 6 mya. (Figures not drawn to scale.) Common hominoid ancestor Common anthropoid 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 4 modern genera of apes: 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. Figure 22.5: Ape evolution. (Figures not drawn to scale.) (c) Dryopithecus, a more advanced ape, may have been ancestral to modern hominoids. Fig. 22-5a/c, p. 470

Apes

Figure 22.6: Apes. Fig. 22-6a, p. 471

Figure 22.6: Apes. Fig. 22-6b, p. 471

Figure 22.6: Apes. Fig. 22-6c, p. 471

Figure 22.6: Apes. 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

Shorter, broader pelvis (front view) Simply curved spine Foramen magnum at the center base of skull Complex curvature of human spine Foramen magnum at the center rear of skull Tall, narrow pelvis (front view) Shorter, broader pelvis (front view) Figure 22.7: Gorilla and human skeletons. When gorilla and human skeletons are compared, the skeletal adaptations for bipedalism in humans become apparent. First toe not aligned with others First toe not opposable, and all toes aligned Gorilla skeleton Human skeleton 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 Figure 22.8: Gorilla and human heads. Incisors Rectangular shape Fig. 22-8a, p. 473

Incisors U-shape Fig. 22-8b, p. 473 Figure 22.8: Gorilla and human heads. 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 Sahelanthropus 6 to 7 million years ago Sahelanthropus small brain face and teeth had many characteristics of larger brained human ancestors

Orrorin Early hominid Orrorin about 6 mya 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

Millions of years ago (mya) H. sapiens H. neanderthalensis Archaic H. sapiens H. erectus A. boisei A. robustus H. ergaster H. habilis A. aethiopicus ? Millions of years ago (mya) A. africanus A. afarensis Figure 22.9: One interpretation of human evolution. This figure does not include hominid fossils earlier than Ardipithecus. Dashed lines show possible evolutionary relationships. A. anamensis A. ramidus Ardipithecus Australopithecus Homo Fig. 22-9, p. 473

Millions of years ago (mya) H. sapiens H. neanderthalensis Archaic H. sapiens H. erectus H. ergaster H. habilis Homo A. boisei A. robustus A. aethiopicus A. africanus A. afarensis A. anamensis Australopithecus ? Millions of years ago (mya) Figure 22.9: One interpretation of human evolution. This figure does not include hominid fossils earlier than Ardipithecus. Dashed lines show possible evolutionary relationships. A. ramidus Ardipithecus 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 Figure 22.10: Homo erectus skull from China. The reconstructed parts are white. Note the receding forehead, pronounced supraorbital ridge, and projecting face and jaws. 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 Anatomically 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