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Chapter 26 Human Evolution

Chapter 26 Human Evolution. 26.1 A Bit of a Neanderthal. Paleoanthropology is the scientific study of prehistoric humans and their relatives Neanderthals ( Homo neanderthalensis ) lived in the Middle East, Europe, and in central Asia as far east as Siberia

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Chapter 26 Human Evolution

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  1. Chapter 26Human Evolution

  2. 26.1 A Bit of a Neanderthal • Paleoanthropology is the scientific study of prehistoric humans and their relatives • Neanderthals (Homo neanderthalensis) lived in the Middle East, Europe, and in central Asia as far east as Siberia • They had a short, stocky build, a long, low braincase, and pronounced brow ridges • DNA studies show that Neanderthal genes exist in several groups of modern humans (Homo sapiens)

  3. Neanderthal and Modern Human

  4. Svante Pääbo with a reconstructed Neanderthal Skull

  5. 26.2 Primates: Our Order • Primates are an order of placental mammals that includes humans, apes, monkeys, and close relatives • Primate characteristics: • Hands and feet capable of grasping • Eyes at the front of the head • Large brains with expanded regions for vision and information processing • Varied diet; four types of teeth • Provide extensive care to young

  6. Origins and Early Branchings • Primates branched into wet-nosed (Strepsirrhini) and dry-nosed primates (Haplorhini) about 50 million years ago • Anthropoidsinclude monkeys, apes, and humans • New World monkeys are climbers with long, prehensile tails that help them maintain balance • Old World monkeys are larger and have no prehensile tail –many spend their lives on the ground • Apes and humans are tailless hominoids

  7. Nonanthropoid Primates: Lemur

  8. Nonanthropoid Primates: Tarsier

  9. Nonanthropoid Primates: New World Monkey

  10. Nonanthropoid Primates: Old World Monkey

  11. Take-Home Message: What are primates? • Primates include lemurs, tarsiers, monkeys, apes, and humans. Most primates are tree-dwellers. Traits such as a flexible shoulder joint and grasping hands with nails are adaptations to a climbing lifestyle. • Compared to other mammals, primates have a relatively large brain with more area devoted to vision and less to smell. • There are two main subgroups. Lemurs and their relatives belong to the subgroup with a wet nose and a fixed upper lip. Tarsiers, monkeys, apes, and humans belong to the subgroup with a dry nose and a movable upper lip.

  12. ANIMATED FIGURE: Primate evolutionary tree To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  13. 26.3 The Apes • Hominoids are tailless primates with an upright posture and relatively large brains • They branched off from a common ancestor with Old World monkeys about 30 million years ago • Proconsul species lived in North Africa about 20 mya • In the Miocene, new species evolved and dispersed to Europe and Asia

  14. Modern Apes • Gibbons (lesser apes) are small apes with elongated arms that inhabit Southeast Asian forests • Great apes include the Asian orangutan and African gorillas, chimpanzees, and bonobos • Gorillas (Gorilla gorilla), the largest living primates, live in forests and feed mainly on leaves • Chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), are our closest living relatives

  15. Gibbon

  16. Orangutan

  17. Gorilla

  18. Chimpanzee

  19. A Human–Ape Comparison • Only members of the lineage leading to humans are bipedal – adapted to walking upright • The human backbone has an S-shaped curve that keeps the head centered over the feet • Human feet have a pronounced arch and a non-opposable big toe • An ape’s spinal cord enters the skull’s base near the rear – a human spinal cord enters near the center

  20. spinal cord attaches at rear of skull C-shaped curve in backbone legs shorter than arms, thighs angle outward flat foot with opposable big toe Figure 26-5a p443

  21. spinal cord attaches at center of skull S-shaped curve in backbone legs longer than arms, thighs angle inward foot with arch, big toe aligned with other toes and not opposable Figure 26-5b p443

  22. ANIMATED FIGURE: Primate skeletons To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  23. A Human–Ape Comparison (cont.) • A human thumb is longer, stronger, and more maneuverable than that of a chimpanzee • Many monkeys and apes grasp objects in a power grip, but only humans routinely use a precision grip for fine manipulation of objects

  24. Power Grip and Precision Grip power grip precision grip

  25. A Human–Ape Comparison (cont.) • The lineage leading to humans underwent a great expansion of the brain • A human brain is three times the size of a chimpanzee brain • The human brain also grows for a longer period after birth, and our offspring receive extended parental care

  26. chimpanzee Figure 26-6a p443

  27. underside of skulls Figure 26-6b p443

  28. human Figure 26-6a p443

  29. underside of skulls Figure 26-6c p443

  30. Take-Home Message: Which human traits are typical of hominoids and which are novel? • Hominoids share a common ancestor with Old World monkeys, but they are generally larger than monkeys, lack a tail, and have an upright stance. Modern hominoids include Asian apes, African apes, and humans. • Upright walking (bipedalism) evolved in the lineage leading to humans. This lineage also shows a trend toward a more maneuverable thumb, a larger and more complex brain, and a longer period of postnatal development.

  31. 26.4 Rise of the Hominins • Hominins are the lineage of humans and all extinct species more closely related to humans than to any other group • Bipedalism is a defining hominin trait – researchers studying hominin origins look for evidence of upright walking • Sahelanthropus tchadensis, 7 mya, western Africa • Orrorin tugenensis, 6 mya, East Africa • Ardipithecus species, 5.8 to 5.2 mya, East Africa

  32. The Hominins Sahelanthropus tchadensis Orrorin tugenensis Ardipithecus kadabba Ardipithecus ramidus Australopithecus anamensis Australopithecus afarensis Australopithecus africanus Paranthropus boisei Homo habilis Homo erectus Homo neanderthalensis Homo floresiensis Homo sapiens 7 6 5 4 3 2 1 Millions of years ago

  33. Ardipithecus ramidus

  34. Australopiths • Australopiths include two genera of hominins that lived in Africa from 4 to 1.2 mya • Australopithecus afarensis lived in Tanzania and other parts of eastern Africa from 3.9 to 3 mya • Footprints indicate that this species had a pronounced arch and a big toe in line with the other toes • A partial skeleton known as Lucy is the best known representative of this species

  35. Bipedal Footprints, 3.6 MYA

  36. Lucy (Australopithecus afarensis)

  37. Paranthropus • Paranthropus descended from an Australopithecus ancestor • Strong teeth and heavily muscled jaws allowed Paranthropus to eat hard and fibrous foods • Paranthropus species are considered close relatives of early humans, but not possible ancestors

  38. Australopithecusafricanus

  39. Paranthropus boisei

  40. ANIMATED FIGURE: Fossils of australopiths To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  41. Factors Favoring Bipedalism • Bipedal walkers move more efficiently across open ground than chimpanzees who move on all fours • Bipedalism keeps the body cooler • An upright stance makes it easier to see predators • Free hands can be used to gather food and carry it from place to place

  42. Take-Home Message:What are hominins? • Hominins include modern humans and extinct members of their lineage. • Possible hominin fossils date back as far as 7 million years ago. Early hominins had small brains. Australopiths are a diverse group of African hominins that probably include human ancestors.

  43. 26.5 Early Humans • When classifying fossil s, scientists who are “lumpers” look for similarities and assign fossils to relatively few species • Scientists who are “splitters” focus on differences and often name new species on the basis of subtle differences • Lumpers place the earliest fossil evidence of our genus, Homo, in two species – splitters divide them into four or more

  44. Homo habilis • Humans are members of the genus Homo • The oldest species is Homo habilis (2.3 mya), though some scientists classify them as a species of Australopithecus • It overlapped in eastern Africa both with australopiths and at least one other species of Homo

  45. Homo habilis

  46. Homo habilis and Australopiths

  47. Homo erectus • Homo erectus appears in the fossil record about 1.8 mya • H. erectus stood on legs that were longer than its arms and had a relatively big brain • H. erectus left Africa and colonized Indonesia by 1.6 million years ago, and China by 1.15 million years ago • Some scientists split Homo erectus fossils into two species: H. erectus in Asia, and H. ergaster in Africa

  48. Homo erectus

  49. Early Culture • Culture is a set of learned behaviors passed from one individual to another, and from one generation to the next • The earliest hominin cultural trait for which we have fossil evidence is toolmaking, probably by australopiths • H. erectus used stone tools to cut up animal carcasses, to scrape meat from bones, and to extract marrow

  50. Homo erectus and Stone Tools

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