1. CHAPTER 8 Primate and Hominin Origins

2. Chapter Outline  Early Primate Evolution  Miocene Fossil Hominoids  Understanding the Human Connection to Other Primates and the Ways We Differ  Discovering Human Evolution: The Science of Paleoanthropology  Early Hominin Tools  Paleoanthropological Dating Methods

3. Chapter Outline  What’s a Hominin?  Walking the Walk: The Bipedal Adaptation  Digging for Connections: Early Hominins from Africa  Pre Australopiths  Australopiths  Closer Connections: Early Homo  Adaptive Patterns of Early African Hominins

4. Focus Questions  Who are the oldest members of the human lineage, and how do these early hominins compare with modern humans? With modern apes?  How do they fit within a biological continuum?

5. Hominins  Colloquial term for members of the tribe Hominini, which includes all bipedal hominoids back to the divergence with African great apes.  Joined by similar behaviors, emphasizing the biocultural nature of human evolution pertaining to the concept that biology makes culture possible and that culture influences biology.

6. Early Primate Evolution  The roots of the primate order go back to the beginnings of the placental mammal radiation at least 65 mya.  The earliest primates date to the Paleocene (65-56 mya) and diverge from quite early primitive placental mammals, called plesiadapiforms.  A vast number of fossil primates from the Eocene (56–33 mya) have been discovered and now total more than 200 recognized species.

7. Eocene Primates  Fossil primates from the Eocene display distinctive primate features.  Looking at the whole array of Eocene primates, it is certain that they were: 1. primates, 2. widely distributed, and 3. mostly extinct by the end of the Eocene.

8. Early Eocene Primates  North Africa fossils dating from the early Eocene (50 mya) and Egypt (37 mya)  Insert Figure 8-2  Darwinius, from the Messel site in Germany, discovered in 2009 and dates to 47 mya, but relationships to living primates are not confirmed

9.  Darwinius, 47 mya

10. Oligocene Primates: Anthropoid Connections  The Oligocene (33–23 mya) has yielded fossil remains of several species of early anthropoids.  By the early Oligocene, continental drift had separated the New World from the Old World.  It’s been suggested that late in the Eocene or very early in the Oligocene, the first anthropoids arose in Africa and reached South America by “rafting” over the water on drifting chunks of vegetation. The ancestry of New and Old World monkeys was separate after 35 mya.

11. Oligocene Primates from Fayum  Apidium  Primitive dental arrangement suggests near or before evolutionary divergence of Old and New World anthropoids  Small, squirrel-like fruit and seed eating, adept at leaping and springing

12. Oligocene Primates from Fayum  Aegyptopithecus  Largest of Fayum anthropoids, roughly the size of a modern howler monkey (13-18 lbs)  Short-limbed, slow-moving  Bridges the gap between Eocene fossils and succeeding Miocene hominoids

13. Major Events in Early Primate Evolution

14. Making Connections  From what you know about primates (chapters 6-7), what evidence indicates a fossil was a primate?

15. Miocene Fossil Hominoids: Closer Connections to Apes and Humans 1. African forms (23–14 mya)  Especially from western Kenya, these hominoids are, in many ways, primitive.  Proconsul 2. European forms (16–11 mya)  From scattered localities in France, Spain, Italy, Greece, Austria, Germany, and Hungary, most are quite derived.  Dryopithecus  Ouranopithecus

17. Miocene Fossil Hominoids 3. Asian forms (16–7 mya)  The largest and most varied group from Turkey through India/Pakistan and east to southern China, most are highly derived.  Sivapithecus

18. Miocene Hominoid Distribution, From Fossils Thus Far Discovered

19. Miocene Hominoid Fossils 1. These hominoids are more closely related to the ape-human lineage than Old World monkeys. 2. Mostly large-bodied hominoids, more akin to the lineages of orangutans, gorillas, chimpanzees, and humans. 3. Most of the Miocene forms discovered are so derived that they are probably not ancestral to any living form.

20. Miocene Hominoid Fossils 4. One lineage that appears well established relates to Sivapithecus from Turkey and Pakistan. This form shows facial features similar to the modern orangutan, suggesting a fairly close evolutionary link. 5. Evidence of definite hominins from the Miocene has not been indisputably confirmed. However, finds from Kenya, Ethiopia, and Chad suggest that hominins diverged sometime in the latter Miocene.

21. Sivapithecus Compared  Comparison of a modern chimpanzee (left), Sivapithecus (middle), and a modern orangutan (right).  Both Sivapithecus and the orangutan exhibit a dished face, broad cheekbones, and projecting upper jaw and incisors.

22. Making Connections  From what you know about primates (chapters 6-7), what evidence indicates a fossil was a hominoid?

23. Biocultural Evolution  All aspects of human adaptation, including technology, traditions, language, religion, marriage patterns, and social roles.  Culture is a set of learned behaviors; it is transmitted from one generation to the next through learning and not by biological or genetic means.  Material culture is part of the cultural complex

24. Paleoanthropology  Paleoanthropology is defined as the study of early humans.  Paleoanthropologists reconstruct the anatomy, behavior, and ecology of our ancestors:  It is a diverse multidisciplinary pursuit seeking to reconstruct every bit of information possible concerning the dating, anatomy, behavior, and ecology of our hominin ancestors.  Locate early hominin sites, collect faunal remains and artifacts

25. Early Hominin Tools  Earliest tools likely made of perishable materials  Hominin bipedalism would have made tools easier to transport  Oldowan-Earliest recognized stone tool culture, including very simple tools, mostly small flakes

26. Oldowan tools

27. Dating Methods  Relative dating methods tell you that something is older or younger than something else  Stratigraphy- based on the law of superposition, which states that a lower layer is older than a higher one  Flourine analysis, used to date remains of bone  Biostratigraphy  paleomagnetism

28.  Paleomagnetic dating

29. Dating Methods  Chronometric (Absolute) dating methods are based on calendar years  K/Ar, or potassium argon method used to date materials in the 5-1 mya range  Carbon-14 method used to date organic material extending back to 75,000 years  Thermoluminescence  Uranium series dating  Electron spin resonance (ESR)

30. What’s a Hominin?  Name for members of tribe Hominini  Refers to all great apes (orangutans, gorillas, chimpanzees, and bonobos) and humans  Defined by dental features, bipedal locomotion, large brain size, and tool making behavior  Characteristics that developed at different rates, called mosaic evolution

31. Traditional Classification of Hominoids

32. Revised Classification of Hominoids

33. Mosaic Evolution  A pattern of evolution in which the rate of evolution in one functional system varies from that in other systems.  In hominin evolution, bipedal locomotion is a defining characteristic; other features such as brain development and behavior become significant in later stages

34. Mosaic Evolution of Hominin Characteristics Locomotion Modern Homo sapiens Bipedal: shortened pelvis; larger body and legs; fingers and toes not as long Early hominin Bipedal: shortened pelvis; differences from later hominins, smaller body and long arms relative to legs; long fingers and toes; capable of considerable climbing Miocene, generalized hominoid Quadrupedal: long pelvis; capable of considerable arm swinging, suspensory locomotion

35. Mosaic Evolution of Hominin Characteristics Brain Modern Homo sapiens Greatly increased brain size—highly encephalized Early hominin Larger than Miocene forms, moderately encephalized; prior to 6 m.y.a., no more encephalized than chimpanzees Miocene, generalized hominoid Small compared to hominins, large compared to other primates; a fair degree of encephalization

36. Mosaic Evolution of Hominin Characteristics Dentition Modern Homo sapiens Small incisors; canines further reduced; molar tooth enamel caps thick Early hominin Moderately large incisors; canines somewhat reduced; molar tooth enamel caps very thick Miocene, generalized hominoid Large front teeth; molar teeth variable, depending on species; some have thin enamel caps, others thick enamel caps

37. Mosaic Evolution of Hominin Characteristics Toolmaking Behavior Modern Homo sapiens Stone tools found after 2.5 m.y.a.; trend of cultural dependency in later hominins Early hominin In earliest stages unknown; no stone tool use prior to 2.5 m.y.a.; more oriented toward tool manufacture and use than chimpanzees Miocene, generalized hominoid Unknown—no stone tools; probably had capabilities similar to chimpanzees

38. Walking the Walk: The Bipedal Adaptation  Efficient bipedalism as the primary form of locomotion is seen only in hominins.  Advantages of bipedalism:  Freed the hands for carrying objects and for making and using tools.  In the bipedal stance, animals have a wider view of the surrounding countryside.  Bipedal walking is an efficient means of covering long distances.

39. Obligate Bipedalism: Structural Alterations

40. Structural and Anatomical Alterations  Pelvis is comparatively much shorter and broader and extends around to the side, stabilizing the line of weight transmission from lower back to hip joint

41. Human Os Coxae  The human os coxae, composed of three bones (right side shown).

42. Ossa Coxae  (a) Homo sapiens.  (b) Early hominin from South Africa.  (c) Great ape.  Note the length and breadth of the iliac blade (boxed) and the line of weight transmission.

43. Structural and Anatomical Alterations  Foot as stable support instead of a grasping limb  Elongated legs to increase the length of stride  Full extension of knee to maintain center of support directly under the body

44. What Makes Us Human?  Knowing that bipedalism emerged in the human lineage well before increased brain size, has your concept of what a human is changed?

45. Finding Early Hominin Fossils  East Africa sites along the Great Rift Valley where more than 2,000 hominin fossils have been found  South Africa sites with geological strata more complex than along the East African Rift Valley

46. Excavation at Sterkfontein  Paleoanthropologist Ronald Clarke carefully excavates a 2-million year-old skeleton from the limestone matrix at Sterkfontein cave. Clearly seen are the cranium and the upper arm bone.

47. Key Pre-Australopith Discoveries DatesRegionHomininsSignificance 4.4 mya East Africa Ardipithecus Aramis Large collection of fossils, partial skeletons; bipedal, bur- derived 5.2–5.8 mya East Africa Ardipithecus Fragmentary, but probably bipedal

48. Key Pre-Australopith Discoveries DatesRegionHomininsSignificance ~6.0 mya East Africa Orrorin Tugenensis First hominid with postcranial Remains ~7.0 mya Central Africa Sahelanthropus Tchadensis Oldest hominid; well preserved cranium; very small-brained; likely bipedal

49. Modern Chimpanzee & Orangutan skulls

50. Sahelanthropus  Small braincase  Vertical face  Huge browridge  Hominin status questioned

51. Ardipithecus  Pelvis shows derived characteristics  Divergent big toe  Woodland environment

52.  Why is it more difficult to identify the earliest potential hominins?

53. Australopiths (4.2–1.2 mya)  The best-known, most widely distributed, and most diverse of the early African hominins are colloquially called australopiths.  This group of hominins is made up of two closely related genera: Australopithecus and Paranthropus.  These hominins have an established time range of over 3 million years, stretching back as early as 4.2 mya and not becoming extinct until apparently close to 1 mya.

54. Australopiths (4.2–1.2 mya)  Major features 1. They are all bipedal (although not necessarily identical to Homo in this regard). 2. They all have relatively small brains (i.e., at least compared to Homo). 3. They all have large teeth, particularly the back teeth, with thick to very thick enamel on the molars.

55. Sectorial lower first premolar  Left lateral view of the teeth of a male patas monkey.  Note how the large upper canine shears against the elongated surface of the sectorial lower first premolar.

56. Laetoli  Dated at between 3.5 and 3.7 mya.  Fossilized hominin footprints were found in an ancient volcanic bed.  Despite agreement that these individuals were bipedal, some researchers feel they were not bipedal in the same way as modern humans.

57. Footprints at Laetoli  Hominin footprint from Laetoli, Tanzania.  Note the deep impression of the heel and the large toe (arrow) in line (adducted) with the other toes.

58. Australopithecus afarensis

59. Infant A. afarensis Skeleton  An important new find of a mostly complete female infant A. afarensis skeleton was announced in 2006.  The discovery was made at the Dikika locale in northeastern Ethiopia, near the Hadar sites.  The infant comes from the same geological horizon as Hadar, dating 3.3 mya.

60. Later More Derived Australopiths (2.5–1.2 mya)  As they adapted to niches, australopiths became more derived and showed physical changes making them distinct from their immediate ancestors.  There were at least three separate lineages of hominins living between 2.5 and 1 mya.  Australopithecus  Paranthropus  Homo

61. Paranthropus

62. Sagittal Crest  A ridge of bone that runs down the middle of the cranium.  This serves as the attachment for the large temporal muscles, indicating strong chewing.

63. A Transitional Australopith?

64. Closer Connections: Early Homo (2.0+- 1.4 mya)  Increased brain size  Associations with stone tools

65. Early Homo Fossil Finds

66. A Tentative Early Hominin Phylogeny

67. Seeing the Big Picture  What explains the pattern of speciation  The evidence is far from complete and significant gaps will remain  Patterns are evident  Early hominin species had restricted ranges; each species exploited a relatively small range and could easily have become separated from other populations of its own species

68.  Most species appear to have been at least partially tied to arboreal habitats, some concentrating on diets of coarse, fibrous plant foods, such as roots  Exploiting such resources may have routinely taken them farther away from the trees

69.  Except for some early Homo individuals, there is very little in the way of an evolutionary trend of increased body size or of markedly greater encephalization; no association of any pre- australopith or australopith hominins with patterned tool use

70.  All early African hominins show an accelerated developmental pattern (similar to that seen in African apes), one quite different from the delayed developmental pattern characteristic of Homo sapiens

71. Why It Matters Question:  This chapter argues that becoming bipedal contributed to the success of our ancestors and to our own success.  So many people have back problems, why hasn’t evolution done a better job of making us into well adapted bipeds?

72. Why It Matters  Answer:  The evolutionary process is a series of trade-offs rather than a course to perfection.  W. M. Krogman discussed the ubiquitous back problems we have as a result of being bipedal. Limb structure evolved over millions of years in quadrupeds and is recently “rigged” to function in an animal walking upright.  Robert Anderson argues for teaching of proper walking techniques, and ways to sit, lift and carry.

73. QUICK QUIZ

74. 1. The primary task of an archeologist at a paleoanthropological site is to a) search for hominin "traces." b) reconstruct the ancient environment of the site. c) establish the relationships of any fossil humans recovered. d) perform dating techniques to establish the time period.

75. Answer: a  The primary task of an archeologist at a paleoanthropological site is to search for hominin "traces."

76. 2. _________________ dating indicates that something is older or younger than something else.

77. Answer: Relative  Relative dating indicates that something is older or younger than something else.

78. 3. The radiometric dating technique used to date material from a few hundred years old to 75,000 years old is ___________.

79. Answer: Carbon-14  The radiometric dating technique used to date material from a few hundred years old to 75,000 years old is ___________.

80. 4. Efficient bipedalism as a primary form of locomotion is only seen in hominins. a) True b) False

81. Answer: True  Efficient bipedalism as a primary form of locomotion is only seen in hominins.