Ch17 Human Origins Notes.docx

The Earth Through Time Chapter 17—Human Origins CHAPTER OUTLINE FOR TEACHING I. Distinguishing characteristics of Humans from Primates A. Body Structure 1. Rounded head shape and relatively flattened face 2. Larger (relative to body size), more complex brain 3. Structural modifications for upright walking 4. Unspecialized teeth 5. Manual dexterity 6. Binocular vision B. Ability Differences and Attributes 1. Intelligence level 2. Language 3. Aesthetic sensibility II. Primates A. Characteristic Physical Attributes 1. 5 digits; opposable digits included 2. Non-specialized teeth 3. No horns, trunks, antlers 4. Relatively large brain B. Characteristic Abilities 1. Grasping and manipulation by hands 2. Good binocular vision and depth perception 3. Upright walking capability C. Modern Suborders 1. Prosimii: tree shrews, lorises, tarsiers, lemurs 2. Anthropoidea: monkeys, apes, humans D. Prosimii Primitive Characteristics: claws, snouts E. Anthropoidea Advanced Characteristics: flat faces, digits, vestigial or real tails 1. Ceboidea (New World monkeys): older branch; not human ancestors; has prehensile tail (spider monkey, marmoset, capuchin) 2. Cercopithecoidea (Old World monkeys): younger branch; ancestors to human lineage; no prehensile tail (macaque, rhesus monkey, Barbary ape, langurs, baboons, mandrills) 3. Hominoidae: apes and humans F. Families of Hominoidae 1. Hylobatidae (primitive branch): gibbons; siamangs 2. Pongidae (advanced branch) a. arboreals: orangutan, chimpanzees b. terrestrials: gorillas 3. Hominidae (hominins): African apes and humans III. Evolutionary Step One: prosimian lineage A. Cretaceous Purgatorius: Hell Creek Fm. (MT) B. Paleocene Plesiadapis: U.S. and France; primitive tooth structure with gap (diastema); claws on digits; extinct by late Eocene C. Eocene Cantitus: Wyoming; shorter snout; grasping toe D. Eocene Notharctus: Wyoming; replaced Cantitus E. Eocene Tetonius: traits like a modern tarsier F. General trends in Eocene evolution of prosimians 1. reduction in muzzle length 2. increase in brain size 3. shifting of eye orbits to more forward position 4. development of a grasping big toe G. Oligocene cooling: forced prosimians out of North America to warmer latitudes (Asia, Africa, southern Indies) IV. Evolutionary Step Two: early anthropoids A. Oligocene Aegyptopithecus zeuxis: Egypt; robust arboreal primate; ape-like 5-cusped molar with Y-shaped troughs between cusps; ape ancestor B. Oligocene-Miocene New World monkeys: South America; independent evolution: 4-cusped molar-like all monkeys C. Oligocene-Eocene Old World monkeys: Eurasia D. Miocene plate tectonics and evolution: closing of Tethys led to cooling and drying of east Africa; grasslands replaced forests; primate evolution thus affected E. Miocene drymorphs: Dryopithecus fontani (France); Proconsul africanus (Kenya); ape-like form F. Middle Miocene Proconsul: ancestor to modern African apes and australopithecine humans G. Middle Miocene australopithecine: Equatorius H. Middle Miocene ramamorph: Ramapithecus I. Late Miocene pongids (chimpanzee, gorilla, and orangutang) J. Common ancestor of apes and hominins: the ramamorphs (Ramapithecus) V. Evolutionary Step Three: australopithecines and hominins A. Australopithecines: robust and gracile forms; upright walking; human stance; robust teeth; brain size of apes (about 600 cm3); used crude tools 1. Chronology of genus Australopithecus a. Sahelanthropus tchadensis: 7-6 million years ago b. Orrorin tugenesis: 6 million years ago; Kenya c. Ardipithecus ramidus: 5.8-5.2 million years ago; Ethiopia d. Australopithecus anamensis: 4.2-3.9 million years ago; Kenya e. Australopithecus afarensis (“Lucy”): 3.9-3.0 million years ago; eastern Africa f. Australopithecus robustus and A. bosei: younger fossils 2. Transition to homonids: increased size of cranial vault; changed position of foramen magnum; narrower premolars, length of tooth row reduced; stone tools associated with fossils a. Homo rudolfensis and H. habilis (a.k.a. H. ergaster): 2.5-2.0 m.y.; savannahs of Africa b. Homo erectus: moved out of Africa into Asia 3. Reasons for australophithecine-homonid transition a. Africa growing cooler and drier 2.7 million years ago b. rain forest transition to grassland c. selective pressures for bipedalism and cerebral abilities B. Hominins: emergent human with human-like teeth; larger brains; social, tool users 1. Beginning of the fossil record for primates: Sahelanthropus tchadensis (Chad; 4 ft tall; 6to 7 m.y. ago; mix of human and ape characteristics) 2. Another early hominin: Orrorin tungenensis (Kenya; 6 m.y. ago; human-like femur) 3. Possible transition species: Australopithecus sediba (South Africa; small brain, but modern human-like hands) VI. Evolutionary Step Four: Homo erectus (“first true humans”); first hominins to move out of Africa A. Chronology of Dispersion 1. Early Pleistocene (1.8 m.y.): H. erectus in Rep. of Georgia 2. Early Pleistocene (1.5 m.y.): H. erectus at west Turkana site (Africa) 3. Middle Pleistocene (0.9 m.y.): H. erectus known in Africa and Europe 4. Late Pleistocene (0.01 m.y.): H. erectus fully dispersed globally B. Trends in Homo erectus Evolution during Pleistocene 1. Brain-size increase: 775 to 1300 cm3 2. Pelvic changes to accommodate birth of larger babies’ head C. Homo erectus Characteristics 1. Prognathous face: sloped forehead, broad flat nose, modern human teeth; chinless 2. Hunters, tool makers, builders 3. Social units or bands 4. Cannibalism or slaughter sites (mass graves) 5. May have used fire in daily life VII. Evolutionary Step Five: Homo sapiens A. Homo sapiens neanderthalensis (Germany): late Pleistocene descendent of Homo erectus; brow ridges; prognathous; chinless jaw; human-like below neck; brain size 1200-1500 cm3 (= human today); “cave man” 1. Activities: cave-dwelling, painting, carving, tool making, rituals of hunting, death rituals 2. Use of fire: heating, cooking, crafting 3. New DNA evidence suggests H. sapiens neanderthalensis may not be so closely related to H. sapiens as previously thought B. Homo sapiens sapiens (Cro-Magnon man; northern Europe): replaced Neanderthals in all regions 34,000 yr ago during last Pleistocene glacial stage; possible Cro-Magnon-Neanderthal “war” or severe competition for resources. 1. Characteristics: vertical brow, projected chin, modern human teeth; modern human skull; brain size 1200-1500 cm3; same cranial type as found today in northern Europe, north Africa, and Canary Islands. 2. Transitional Neanderthal-Cro-Magnon forms: Palestine, South Africa, Germany, Czech Republic a. Neanderthal-Cro-Magnon evolution outside Europe b. Cro-Magnon migration into Europe and Asia during slight glacial retreat 35,000 yr ago 3. Activities: tool making, painting, rituals, hunting, engraving, sculpting, burial ceremony, ornaments and clothing, cultivation of plants and animals, tribal activities 4. Evidence of higher thought: complexity of rituals, tribal organization, variety of tools and items created, intricate clothing, skill levels, language and symbols 5. Migration of aboriginal people into North America a. likely timing near end of last Pleistocene glaciation when sea level was lower b. enter across Bering Straits (land bridge between Asia and North America) c. evidence of west coast and Alaska occupation: flints and campfires 30,000 to 23,000 yr old 6. Paleo-Indians of late Pleistocene a. Clovis and Sandia (NM) sites: tools dated at 11,000 and 13,000 yr b. Folsom Culture: 9,000-11,000 yr ago C. Homo floresiensis (little people of the southern Pacific) VIII. Human Population Growth A. Change over Time 1. Estimate at end of Pleistocene (10,000 yr ago): 6 million humans 2. Current population: 7 billion 3. Projection for year 2050 A.D.: 9 billion humans B. Depletion of Resources 1. 20% topsoil now used up 2. 33% forested areas lost in last 50 yr 3. 12.5% agricultural land destroyed by overgrazing 4. Massive loss of soil productivity 5. 5% reduction in ozone layer 6. 33% increase in greenhouse gas since industrial revolution 7. Water shortages becoming common 8. Depletion of many key mineral resources C. Future Goals to Sustain Quality Life 1. Reduce population growth; stabilize world population 2. Reforestation and land conservation 3. Pollution reduction 4. Recycling of mineral and other resources Answers to Discussion Questions 1. Hominoidea and hominidae are distinguished as superfamily and family, respectively, of humans. Hominoidea includes three families (hylobatidae, pongidae, and homonidea). Modern primates are divided into suborders Prosimii (includes tree shrews, lorises, and tarsiers) and Anthropoidea (includes monkeys, apes, and humans). The hylobatidae and pongidae are families within the super family hominoidea. Hylobatidae includes gibbons and siamongs. Pongidae includes orangutans, chimpanzees, and gorillas. Ceboidea and cercopithecoidea are two superfamilies that, along with hominoidea, make up the suborder Anthropoida Ceboidea includes howler monkeys, spider monkeys, capuchin, common marmosets, and pinche monkeys. Cercopithecoidea includes macaque, baboon, wanderloo, common langur, and proboseis monkey. 2. The close-set eyes and grasping hands are anthropoid characteristics that allowed vision in three dimensions and manipulation of objects with the hands (with feet). 3. The first robust arboreal primates were Aegyptopithecus, an Oligocene fossil. The four-legged ancestral primate was Proconsul, a middle Miocene fossil. The first upright-walking, two-legged primate was Ardipithecus ramidus, an early Pliocene fossil. The first specimens of Homo are about 2.5 million years old (Pliocene). 4. Chert (and its variety flint) made excellent spear points, axes, and scrapers because those materials break easily into sharp fragments which hold a sharp edge for a long time. 5. The lack of vegetation in the desert regions of eastern Africa combined with dateable interlayered volcanic ash and lava flows make finding and dating fossils easier there. Eastern Africa is a key site of long-term hominoid occupation, unlike other parts of the world. 6. Australopithecus’ human-like traits were pelvis and leg bones that indicate upright walking and tooth structure (dentition). Their apelike characteristics were small stature, skull shape (jaw thrust forward and no chin), and small cranial capacity (about 800 cm3). 7. Cro-Magnon people (Homo sapiens sapiens) were taller, had more vertical brow, projecting chin, and changed tooth arrangement. They also perfected stone and bone tool manufacture, produced carving, sculpture, and cave art, and developed ornaments to be worn. These characteristics set them apart from Neanderthal people whom they displaced. 8. The Paleocene Pleisadapis (prosimian) skull contains primitive teeth with a distinctive gap (diastema) between incisors and cheek teeth. The overall skull shape was rodent-like, that is tapered to a snout. During Eocene, prosimian snouts grew shorter (e.p.g., Cantitus and Notharactus). During Oligocene, anthropoids like Aegyptopithecus (a robust arboreal primate) developed 5-cusped molars and a snout-less, ape-like face. This facial type characterizes Miocene forms like Dryopithecus and Proconsul. Pliocene Australopithecus species showed larger brain capacities (600-700 cm3) robust teeth, brow ridges, prognathous brow, and chinless jaw. Pleistocene Homo erectus and subsequent Homo sapiens neanderthalensis had similar features of the skull but the brain capacity was 775 to 1300 cm3 and 1200 to 1500 cm3, respectively. Thus there was a progressive increase. Modern humans, Homo sapiens sapiens developed a vertical brow, distinctive chin, and modern cranial shape (volume = 1200-1500 cm3) approximately 34,000 yr ago. 9. Homo sapiens sapiens migrated into the New World (i.e., the Americas) via the Bering Strait land bridge near the end of the last glacial cycle 12,000 to 18,000 yr ago. It makes most sense to assume they migrated during a glacial maximum when the most dry land would have been exposed on the shelf area of the Bering Strait. The Bering connection is the only possible Asian-American connection. Radiocarbon dates of most ancient human-fossil sites in western North America cluster about this time (12,000-18,000 yr). A brief warm spell during a glacial interval would be best so that long-distance migration would be easier physically. However, a full interglacial warming would likely have raised sea level to the height where the land bridge was flooded. 10. Life will potentially be more difficult for people in the year 2050 if population trends are left unchecked. Degradation trends in topsoil quality and quantity, forested areas, grazing tracts, ozone chemistry, greenhouse gas balance, water quality and quantity and key mineral resource availability all spell trouble for the future. If global goals of curtailing population growth, reforestation, land conservation, pollution reduction, and resource recycling can come about, the year 2050 may not seem so bleak as technological advance may catch up to help us affect solutions to adequately support a large but stable global population well above current levels. 11. The area experienced numerous volcanic eruptions during this interval of geological history and the ash falls from these eruptions mixed with water make excellent material to preserve fossil remains and imprints of human footprints. The volcanic ash is very each to date radiometrically and this provides excellent age control for these fossil finds. 12. c 13. b 14. e Chapter Activities Student activities for in-depth learning. 1. According to this February, 2009, New York Times article (http://www.nytimes.com/ 2009/02/13/science/13neanderthal.html), what have recent studies of the Neanderthal genome suggested to scientists about the nature and abilities of this early human form? 2. According to this National Geographic Society 2009 news article (http://news.nationalgeographic.com/news/2009/02/090226-oldest-footprints.html), what has the discovery of these oldest human footprints in Africa told us about the abilities of humans and their life style of 1.5 million years ago? Chapter 17—Human Origins CHAPTER OVERVIEW This chapter concerns the evolutionary history of man. It begins by describing the unique characteristics shared by humans such as an enlarged brain and an opposable thumb which can be used to manipulate objects between the fingers and thumb. These, along with other characteristics, set humans apart as a superior, but not always a wiser competitor. Modern primates are discussed as well as a comprehensive classification of Order Primates. The early fossil record begins with prosimians (lemurs and tarsiers) of Paleocene and Eocene. The more advanced anthropoids (ape like) appeared during Miocene, while the earliest hominid line (dryomorphs), who display features shared by both apes and hominids, came later. In the interval from late Pleistocene to early Pleistocene hominids passed through three major stages of evolution. The first stage, early Pleistocene saw the evolution of Australopithecine. The second stage occurred during middle Pleistocene and is represented by Homo erectus, commonly known as “Peking” or “Java” man. Late Pleistocene marked the rise of Neandertal and Cro-Magnon followed by our own species, Homo sapiens. This chapter emphasizes the anatomical differences and relationships among Australopithecine, Neandertal, and Cro-Magnon using some of the more recent finds, radiometric dating, and geographic locations of those finds. This chapter concludes with the arrival of humans in the Americas and some of the population challenges we are facing in the future. LEARNING OBJECTIVES By reading and completing information within this chapter you should gain an understanding of the following concepts: Describe some of the characteristics of the primate order and explain why the prosimians (lemurs and tarsiers) and anthropoids are placed in this order. Discuss the evolutionary importance of prosimians. Explain the evolutionary significance of dryomorphs including why these early apes are considered ancestral to modern apes and the hominid line. Discuss the significance and characteristics of Proconsul africanus including their probable descendants. Discuss the evolutionary history of Homo erectus, including the biological (skull) characteristics that set him apart from Homo sapiens. Explain the biological differences and relationship between Australopithecines and Homo sapiens. Describe the anatomical differences and similarities of Homo sapiens, Neanderthal, and Cro-Magnon. Explain the worldwide consequences of over population. Describe the finiteness of our water resources, mineral resources, and other material resources. Discuss the Internet sources that deal with the following: the quality of water in your area, the consumption of mineral resources per capita in this country and abroad, and the mineral resources mined in this county other than coal, gas, and petroleum. CHAPTER OUTLINE Primates Primate Characteristics Modern Primates Prosimii Arthropoidea Primate Beginnings The Early Arthropoids The Australopithecine Stage and the Emergence of Hominids “Lucy” (Australopithecus afarensis) Rich African Fossil Sites Genus Homo The Homo Erectus Stage Final Stages of Human Evolution The Neandertals Little People of the South Pacific Cro-Magnon People Beginnings of Recorded History Humans Arrive in America Human Population: 7 Billion and Growing Key Terms (pages given in parentheses) Anthropoidea (545): The suborder of primates that includes monkeys, apes, and humans is known as anthropoidea. aboreal (544): Tree-dwelling animals such as squirrels, civets, and opossums that lack the short face, close-set eyes, and opposable digits. australopithercene (553): A general term applied loosely to Pliocene and early Pleistocene primates whose skeletal characteristics place them between typically ape-like individuals and those more obviously human. These were the first hominids. brachiating (545): Term applied to monkeys, apes, etc. that swing from branch to branch and tree to tree by using limbs. Ceboidea (546): The New World monkeys, characterized by prehensile tails, and including the capuchin, marmoset, and howler monkeys. Cercopithecoidea (547): The Old World monkeys (of Asia, southern Europe, and Africa), including macaques, guenons, langurs, baboons, and mandrills. Clovis culture (564): An archeological site in New Mexico that supports evidence that human population lived in North America about 12,000 years ago. This evidence is supported by stone tools and weapons. Cro-magnon people (561): Humans that replaced the Neanderthals during the fourth glacial stage. The new breed, designated Homo sapiens, was mostly taller than their predecessors, had a more vertical brown, and had a decided projection to the chin. dryomorphs (551): Miocene primates that varied in size and appearance. These small primates are decidedly ape-like rather than monkey-like. hominids (Hominidae) (545): Group of early humans that provide an unsurpassed record of human evolution over the past 4 million years. Hylobatidae (547): A group of persistently arboreal, small apes that are exemplified by the gibbons and siamangs. Neanderthals (557): Early humans, of which fossils have been found that indicate that the Neanderthal people ranged across the entire expanse of the Old World. With their heavy brow ridges and prognathous, chinless jaws, Neanderthals have become the very personification of the “cave man.” nocturnal (546): Broad term that applies to animals that feed at night. Many possess eyes that are exceptionally large and positioned toward the front to provide stereoscopic vision. Pongidae (547): A group of tail-less apes consisting of orangutans, chimpanzees, and gorillas. prehensile (tail in primates) (546): Term that applies to New World monkeys that have tails that can be wrapped around branches. primates (544): an order of mammals that include members that have enlarged brains, a modification of the hand (an opposable thumb), foot, thorax, and binocular vision. prognathous (557): Term used for the condition found in Homo erectus in which the forehead sloped, and the jaw jutted forward at the tooth line. Prosimii (545): A suborder of primates including the less advanced primates, such as lemurs, tarsiers, and tree shrews. ramamorphs (552): A group of Miocene apes thought by many to be the common ancestral stock for both later apes and hominids. Human Origins 2 INTRODUCTION ?Humans, Homo sapiens, meaning "thinking man" or "intelligent human," appeared during the latter part of Cenozoic, during Pleistocene. ?Homo sapiens share many characteristics with the other members of the Order Primates, including basic body structure and biochemistry. 3 CHARACTERISTICS OF HOMO SAPIENS Humans are distinct from the other primates : ?Larger, more complex brain ?Stand and walk erect due to structural modifications to vertebral column, legs & pelvis ?Flatter face ?Teeth less robust ?Greater manual dexterity, leading to ability to manufacture and use sophisticated tools ?Greater intelligence, leading to language and culture 4 ORDER PRIMATES ?Primates are placental mammals. ?They have five digits, which is a primitive, non-specialized characteristic. ?They have not developed hoofs, horns, antlers, or trunks, unlike some other groups of placental mammals, and so they remain structurally generalized compared with other mammalian groups. 5 ADAPTATIONS OF THE PRIMATES ?Rounded head shape ?Progressive enlargement of the brain ?Shortening and flattening of the face ?Unspecialized teeth ?Eyes are close-set and positioned toward front of face. Binocular stereoscopic vision. Ability to judge distance. 6 ADAPTATIONS OF THE PRIMATES ?Modifications of the hand - opposable thumb ?Mobility of the forearm, so hand can be turned ?Modifications of the thorax for upright posture ?Forelimbs and hind limbs diverged in form and function 7 Right hand of the Eocene prosimian Europolemus. The hand shows key primate characteristics: broad fingertips and an opposable thumb (the thumb can be touched to each of the other fingertips). Right hand of a human (palm up). The human hand is not used in locomotion. It can be used to manipulate small objects between the fingers and thumb. THE OPPOSABLE THUMB FIGURE 17-2 8 TYPES OF MODERN PRIMATES 1.Prosimians - tree shrews, lemurs, lorises, and tarsiers 2.Anthropoidea - monkeys, apes, and humans a.Monkeys i.New World monkeys ii.Old World monkeys b.Hominoidea or anthropoid apes 9 PROSIMIANS ?Tree shrews, lemurs, lorises, and tarsiers ?Tree shrews and lemurs have long snouts and eyes on the sides of the head. Most digits have claws. ?Tarsiers have relatively flat face, close-set eyes for stereoscopic vision, and fingers and toes have nails rather than claws. lemurs tarsier 10 ?Not involved in evolution of humans ?Includes spider monkey, capuchin, and marmoset. ?Prehensile tails ?Oldest fossils are Oligocene from South America NEW WORLD MONKEYS (A) Art Wolfe/Photo Researchers, Inc., (B) Jany Sauvanet/Photo Researchers, Inc., (C) Gregory G. Dimjian/Photo Researchers, Inc 11 OLD WORLD MONKEYS ?Baboons, mandrills, macaques, rhesus monkeys, Barbary apes ?Nostrils close together and directed downward, as in humans ?Tail not prehensile 12 Macaque Baboons Barbary apes OLD WORLD MONKEYS (left) Richard T. Nowitz/Photo Researchers, Inc.; (center) Tom McHugh/Photo Researchers, Inc.; (right) Len Rue, Jr./Photo Researchers, Inc. 13 HOMINOIDEA OR ANTHROPOID APES ?Tail-less primates ?Gibbons, orangutans, chimpanzees, bonobos, gorillas, and humans ?Modern species evolved from same ancestral stock that produced humans ?DNA evidence indicates divergence from human line 5-7 million years ago. ?DNA of chimpanzees and humans is 98.4% similar. ?Similarities in the proteins hemoglobin and myoglobin indicate that the chimpanzee is our closest relative. 14 HOMINOIDEA OR ANTHROPOID APES Three families: ?Hylobatidae - Gibbons The most primitive branch of tail-less apes. ?Pongidae - Orangutans, chimpanzees, gorillas, and bonobos. ?Hominidae - Humans 15 ANTHROPOID APES ?Gibbon ?Gorilla Orangutan? Chimpanzees? (top left) David Maitland/Getty Images, Inc.; (top right) Tom McHugh/Photo Researchers, Inc.; (bottom left) Andrew Dernie/Getty Images, Inc.; (bottom right) Photodisc/Getty Images, Inc.) 16 PROSIMIAN VANGUARD ?Earliest fossil record for primates is Purgatorius, known from the Upper Cretaceous Hell Creek Formation at Purgatory Hill, Montana. The earliest primates lived during the time of the last of the dinosaurs. ?The Paleocene Plesiadapis is the only primate genus other than Homo to inhabit both the Old World and the New World. This suggests that the continents were not fully separated by Paleocene. 17 PROSIMIAN VANGUARD During Eocene, primates underwent: ?Reduction in length of face ?Increase in brain size ?Movement of eyes to more forward position ?Development of a grasping big toe 18 PROSIMIAN VANGUARD ?Tarsiers and lemurs were abundant and widely distributed on Northern Hemisphere continents during Eocene. ?When the climate cooled during Oligocene, the primates virtually disappeared from North America. They were forced southward into Asia, Africa, and the East Indies. 19 EARLY ANTHROPOIDS ?Anthropoids are the higher primates - monkeys, apes, and humans ?Early anthropoid fossils are found in Oligocene rocks (33-34 m.y. old) at Fayum, Egypt. ?Aegyptopithecus = robust arboreal primates with a monkey-like tail and limbs, and eyes on the front of the skull. ?The prosimian-anthropoid transition had occurred by Oligocene. Oligocene ape, Aegyptopithecus 20 PRIMATE EVOLUTION ?During Miocene (23 - 5 m.y. ago), plate tectonics affected primate evolution. ?Africa and Arabia drifted northward and collided with Eurasia. This changed the circulation in the Tethys Sea and the climate in East Africa became cooler and drier. ?Grass-covered plains replaced tropical forests. 21 PRIMATE EVOLUTION ?As a result of the change in climate and vegetation, adaptive radiation occurred among the Old World primates. ?During late Miocene, primates appeared that gave rise to the pongids (orangutan, chimpanzee, and gorilla) and the hominids (human family). ?A new group, the dryomorphs (formerly dryopithecines) appeared during Miocene. 22 THE DRYOMORPHS - PROCONSUL ?Proconsul, discovered by the Leakeys in 1948 in Kenya, was a dryomorph or a dryomorph ancestor. ?It had ape-like skull, jaws, and teeth. It had monkey-like long trunk, arms and finger bones. ?Middle Miocene descendants of Proconsul are probably ancestral to modern African apes and the first hominids, the australopithecines. Miocene drymorph, Proconsul 23 PRIMATE EVOLUTION ?By about 18 million years ago, Africa collided with Eurasia and primates migrated into Eurasia and diversified. ?These primates include the following Miocene apes, called ramamorphs, which are considered to be ancestral stock for both later apes and hominids: ?Ramapithecus ?Sivapithecus ?Gigantipithecus 24 PRIMATE EVOLUTION ?Interpreting the primate family tree is complicated. There are many splits and dead ends. ?The story must be reinterpreted each time new types of fossil primates are discovered. 25 RICH FOSSIL SITES OF AFRICA Rich hominin fossil sites in East Africa. Beds of volcanic ash between fossil beds facilitate radioisotope dating in this region, and dry conditions limit the amount of vegetation covering bone beds. 26 AUSTRALOPITHICINES ?Australopithecus africanus was discovered in 1924 by Raymond Dart in South Africa. Since then, many specimens have been discovered in East Africa, particularly in Olduvai Gorge by Mary and Louis Leakey. ?East African fossil sites have yielded hundreds of hominid bones, documenting human evolution over the past 4 million years. ?Interbedded volcanic ash allows radiometric dating of the hominid fossils using potasium-argon method. 27 AUSTRALOPITHECUS AFRICANUS Australopithecus africanus skull, from the Transvaal region, South Africa. 28 ?Oldest hominid fossils are 6-7 million years old, from Chad, Sahelanthropus tchadensis. ?Prior to this fairly recent discovery, the oldest know hominids were 5.8-5.2 million years old. Ardipithecus ramidus from Ethopia. ?Australopithecus anamensis lived from 4.2 to 3.9 m.y. ago. It appears to be an evolutionary intermediate between Ardipithecus ramidus and Australopithecus afarensis or "Lucy." AUSTRALOPITHICINES 29 "LUCY" AUSTRALOPITHECUS AFARENSIS ?Discovered by Donald Johanson in 1974 and nicknamed "Lucy." ?Lucy was a 3.5 foot tall erect-walking hominid in East Africa about 3.5 million years ago. Posture is determined from analysis of pelvic and leg bones. ?Resent excavations for Australopithecus afarensis have yielded a skeleton of a male that was about 5.5 feet tall. 30 "LUCY" AUSTRALOPITHECUS AFARENSIS ?Further evidence of bipedalism (walking upright on two feet) of australopithecines is the discovery of footprints and a trackway in 3.2 m.y. volcanic ash layers (a Pliocene tuff) at Laetoli, eastern Africa. ?Australopithicine dentition (tooth structure) was essentially human. Cranial (brain) capacity was less than that of modern humans. (600 cm³ vs. 1400-1600³ in modern humans). 31 AUSTRALOPITHECUS AFARENSIS Evidence for bipedalism. (A) Footprints probably made by Australopithecus afarensis about 3.5 million years ago as a pair of these hominins walked across wet volcanic ash. The footprints document the ability of hominins to walk on two legs. The tracks were discovered in 1976 by Mary Leakey. (B) A female and male stroll the Late Pliocene landscape of eastern Africa, leaving telltale footprints in the ash, much as vacationers leave footprints on a wet beach. 32 TWO TYPES OF AUSTRALOPITHICINES ?Gracile - Smaller, lighter-bodied with smaller teeth. Includes Australopithecus afarensis (Lucy). This group is transitional to genus Homo. ?Robust - Larger, heavy-bodied with larger teeth. Includes Australopithecus boisei (sometimes called Paranthropus boisei) and Australopithecus robustus (sometimes called Paranthropus robustus). Both are evolutionary side branches. 33 ?Opinions differ as to whether the boisei and robustus species should be included in genus Australopithecus. ?The current consensus in the scientific community is that they should be placed in a separate genus, Paranthropus, which appears to have developed from the australopithecines. ?The robust australopithecines are now reclassified as belonging to genus Paranthropus. TWO TYPES OF AUSTRALOPITHICINES 34 ?New discover near Johannesburg, South Africa named Australopithecus sediba ?Skeletal remains of the young male and an adult female. ?Intermediate between australopithecine and genus Homo. ?Australopithecine traits – small brain size, shoulder bones, and long arms. ?Homo traits – modern hands and less flared pelvis TRANSITION BETWEEN AUSTRALOPITHICINES AND HOMO 35 TIMELINES FOR PLIOCENE AND PLEISTOCENE HOMININS. 36 GENUS HOMO ?The genus Homo arose nearly 2.5 million years ago when australopithecines evolved into the ancestors of humans, Homo ergaster, also called Homo habilis. ?Homo rudolfensis and Homo ergaster or Homo habilis lived in Africa around 2 million years ago. Homo rudolfensis 37 GENUS HOMO ?The evolutionary transition may have been stimulated by the change to a cooler, drier climate about 2.7 million years ago. ?Rainforests were replaced by grasslands. ?In this environment, selective pressures may have led to bipedalism, greater intelligence, and the ability to make stone tools. Stone tools are found with fossils of Homo. 38 GENUS HOMO ?Genus Homo has a larger cranial capacity and some smaller teeth, but no striking anatomical differences. ?Homo erectus arose from Homo ergaster or Homo habilis. ?The opening at the base of the skull, where the spinal cord joins the brain, called the foramen magnum, is in a more forward position in Homo erectus, indicating that it had a more erect posture. 39 THE HOMO ERECTUS STAGE ?Homo erectus fossils include: ?A 1.8 million years jaw in the Caucasus Mountains of Georgia ?A 1.5 million years complete skeleton from east Africa near Lake Turkana (long-limbed, tall and slender with a remarkably modern skeleton) ?A 750,000 year old skull cap from Olduvai Gorge 40 ?Homo erectus lived in the early to middle Pleistocene ?Homo erectus is the first hominid known to have moved from Africa into Eurasia. ?A rapid increase in brain size had begun in Homo erectus. ?Homo erectus was a toolmaker and hunter. It is unclear whether they had language, wore clothes, built dwellings or used fire. THE HOMO ERECTUS STAGE 41 HOMO ERECTUS SKULL CHARACTERISTICS ?Cranial capacity was 775 - 1300 cm³, slightly less than (or overlapping the lower range of) that of modern humans. ?Skull was rather massive and flat ?Heavy, bony supraorbital (brow) ridges ?Sloping forehead ?The jaw jutted forward at the toothline, a condition called prognathous ?The nose was broad and flat ?The teeth were robust but essentially modern ?Lacked a jutting chin 42 HOMO ERECTUS AND TOOLS Progressive improvement in tool-making from stone during the Pleistocene. The crude stone tools of the Early Pleistocene (bottom) were produced by australopithecines. Homo erectus produced the better-shaped tools of the Middle Pleistocene. The Upper Paleolithic tools included carefully chipped blades and points. FIGURE 17-26, 43 HOMO ERECTUS AND FIRE A group of Homo erectus people using fire to make tools while others return from hunting. 44 THE NEANDERTALS ?Late Pleistocene hominids are called Neandertals. ?Neandertals may be a subspecies of Homo sapiens, designated as Homo sapiens neandertalensis. 45 NEANDERTAL SKULL CHARACTERISTICS ?Brain size equal to or larger than that of modern humans ?Heavy supraorbital ridge (brow ridge) ?Prognathous (face extends forward at toothline) - but not as much as Homo erectus. ?No chin - but lower jaw not as receding as that of Homo erectus ?Enlarged nasal cavity (for warming cold inhaled air) 46 NEANDERTAL SKULL CHARACTERISTICS Skull of a classic Neandertal. From the Homo erectus stage of the Middle Pleistocene. Neandertals roamed central Europe as recently as 28,000 years ago. This is indicated by the radiocarbon date for this Neandertal jawbone from a cave site in Croatia. 47 NEANDERTAL CHARACTERISTICS Neandertal skeleton (A) assembled from actual skeletal bones compared with skeleton of a modern human. (B) The Neandertal’s flaring rib cage provided space for large lungs, needed for a high level of activity. Reconstruction of a Neandertal family group. 48 WHEN DID THE NEANDERTALS LIVE? The Neandertals can be divided into three groups. ?Early Neanderthals, that lived approximately 250,000 to 130,000 years ago ?Neanderthals that existed during the transition to the Upper Paleolithic, approximately 130,000 to 45,000 years ago ?Late-surviving Neanderthals after 45,000 years ago, up until about 28,000 years ago. 49 NEANDERTALS AND MODERN HUMANS ?In central Europe, Neandertals coexisted with early modern humans for thousands of years. ?Neandertal skeletons were somewhat more robust than human skeletons. 50 NEANDERTALS AND MODERN HUMANS ?Bones discovered in 2002 show a mix of human and Neandertal traits, suggesting interbreeding. Skull comparison. (A) Neandertal. (B) Skull from a rock shelter on the slope of Mount Carmel (Israel) that appears to show both Neandertal and Cro-Magnon features. (C) Cro-Magnon. The Mount Carmel skull is intermediate in both form and age between Neandertal and Cro-Magnon. 51 NEANDERTAL CULTURE 1.Neandertals hunted cold-tolerant mammals including cave bears, mammoths, wooly rhinos, reindeer, bison, and aurochs (a type of cattle). 2.They manufactured a variety of stone tools 3.They used fire, which provided light in caves, gave warmth, allowed the thawing and cooking of food, and provided protection from predators. 52 NEANDERTAL CULTURE 4.They constructed shelters or houses of skins, sticks and bones. 5.They cared for the sick. 6.They buried artifacts with the dead, suggesting a belief in an afterlife. 7.Musical instruments have also been found in association with Neandertal remains, such as a flute made from a bone, dating to between 82,000 and 43,000 years ago. 53 LITTLE PEOPLE OF THE SOUTH PACIFIC ?A new species of human was discovered on the Indonesian island of Flores in 2004, Homo floresiensis. ?An excavation produced the remains of seven small individuals. ?The adults were only 3 ft (1 m) tall. 54 LITTLE PEOPLE OF THE SOUTH PACIFIC ?Homo floresiensis lived as recently as 13,000 years ago, at the same time as both the Neandertals and modern humans. ?They hunted, used fire, and made stone tools. ?The ancestry of this species is uncertain, however, Homo erectus probably reached the island about 800,000 years ago, and evolved into a smaller species as a result of living on an island with limited food and few large predators. 55 THE EARLIEST HUMANS ?Fossil evidence from along the Omo River in southern Ethiopia shows that modern humans, Homo sapiens, lived in Africa as much as 195,000 years ago, according to an article published in February 2005 ?Previously, modern humans were thought to have appeared in Africa about 160,000 years ago ?Humans appeared in Africa many thousands of years before our species appeared on any other continent 56 THE EARLIEST HUMANS ?There appears to have been a time gap between the appearance of the modern human skeleton and modern types of behavior resulting in cultural artifacts. ?Stone knife blades appeared between 200,000 and 50,000 years ago. ?Other types of cultural artifacts, however, appeared just 50,000 years ago. 57 OUT OF AFRICA ?Humans left Africa between about 40,000 and 50,000 years ago, and appear to have taken culture with them, including things such as bone carving, tools such as harpoons, jewelry and ornamentation, artwork, and arrowheads. 58 CRO-MAGNON ?About 34,000 years ago during a glacial advance, humans closely resembling modern Europeans moved into the area occupied by the Neandertals, and eventually replaced them. ?They are Homo sapiens, and are called Cro-Magnon. 59 CRO-MAGNON ?Characteristics of Cro-Magnon: ?Mostly taller than Neandertals ?More vertical forehead ?Jutting chin Cro-Magnon skull, 30,000 years old 60 CRO-MAGNON CULTURE Cro-Magnon continued and further developed the cultural traditions of the Neandertals: ?Manufactured a greater variety of stone tools ?Painted pictures of animals in caves ?Carved and sculpted images of women and animals from bone or ivory ?Made and wore jewelry ?Elaborately buried their dead (such as burying hunters with their weapons) ?Practiced rituals and believed in afterlife ?Hunted and gathered edible plants 61 CRO-MAGNON CULTURE Prehistoric art by Late Pleistocene Homo sapiens. (A) “The Venus of Willendorf”—probably a fertility figure—found in Austria. (B) A tool called a thong-stropper, used either to work thongs made from hide or to straighten arrow shafts. The tool is made from an antler and is intricately carved. 62 BEGINNINGS OF RECORDED HISTORY About 15,000 -10,000 years ago, humans began to: ?Domesticate animals ?Cultivate plants ?Produce more highly developed tools ?Make utensils of fired clay ?Develop permanent settlements ?Use language ?Develop writing With the development of writing, the era of recorded history began. 63 COMING TO AMERICA ?Humans in the Americas are called Paleoindians. ?It is not definitely known when the first human set foot in America. ?The widely held view is that humans arrived in the Americas from Asia, crossing the Bering Land Bridge between Asia and Alaska between 10,000 and 25,000 years ago (to perhaps 30,000 years or more), during a glaciation which lowered sea levels. 64 PRE-CLOVIS PEOPLE ?Stone weapon points and tools in Meadowcroft Shelter, western Pennsylvania, appear to be 19,600 years old. ?Some South American sites are 13,000 years old or older. 65 ARRIVAL OF THE CLOVIS PEOPLE ?Stone tools of the Clovis culture, about 13,000 years old, are known from Alaska to South America. They occupied sites in the Americas for over 2,000 years. ?The Clovis people dominated for several thousand years, and then a new group, the Folsom people took up residence in North America about 11,000 years ago. 66 HUMAN POPULATION – 7 BILLION AND GROWING Human survival may depend on our ability to slow the rate of population increase. 67 WHAT LIES AHEAD? ?Humans have existed for about the past 2 million years out of the Earth’s 4.6 billion year history. Will humans match the Dinosaurs lineage of 140 million years? ?Global climates and sea level will be influenced by both human (green house gases) and natural (Milankovitch cycles) processes. ?The Earth is still tectonically active with the Atlantic ocean basin continuing to widen, Africa moving north to collide with Europe, and the Baja Peninsula on an Alaskan cruise. ?In 7 billion years the Sun will expand as part of the red giant phase and engulf the Earth.