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Chapter 15

Chapter 15. HOMININ EVOLUTION Page 565 - 619. Classification Hierarchy. Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapiens. A MAMMAL:. Humans are Primates.

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Chapter 15

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  1. Chapter 15 HOMININ EVOLUTION Page 565 - 619

  2. Classification Hierarchy Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapiens

  3. A MAMMAL:

  4. Humans are Primates • No single feature is diagnostic of a primate but, taken together the following features identify a primate:- • Hands and feet typically have five digits that can grasp or curl objects, and thumbs and/or toes are opposable. • Flat nails on their digits with the tips of their digits able to gain information through the sense of touch.

  5. PRIMATES • Large forward facing eyes that give 3D vision as well as colour because they have cones in the retinas of their eyes. • A protective bone at the outer side of the eye socket. • Flexible skeletons. • Large brains compared to body size. • Social animals and live in groups. • Relatively long gestation period.

  6. Early Primates • Prosimians (65mya) • Monkeys (35mya) • Apes (23mya) • Hominids (5mya)

  7. EVOLUTION OF PRIMATES

  8. PRIMATE FAMILY TREE Crown lemur Orangutan

  9. PRIMATE TRAITS • Common physical primate traits: • dense hair or fur covering • warm-blooded • live young • suckle • infant dependence • Common social primate traits: • social life • play • observation and imitation • pecking order Common Primate Traits

  10. Evolution of the primate • Living primates have evolved form an ancestral species over a period 65 – 85mya. • During primate evolution, lines that gave rise to different groups of modern primates diverged at various times. • It is estimated that the line that led to modern humans diverged from the line that led to modern chimps about 5 – 7 mya. • Times of divergence are estimated using DNA sequences.

  11. EVOLUTION OF PRIMATES • The evolution of primates is characterized by trends towards: • mobile limbs • grasping hands (with opposable thumbs) • a flattened face • binocular vision • a large, complex brain (for learned behavior) • a reduced reproductive rate

  12. PRIMATE LIMBS • Most primates have flat nails as well as sensitive pads on the undersides of fingers and toes. • Many also have both an opposable big toe and thumb. • Mobile limbs and clawless opposable digits allow primates to • freely grasp and release tree limbs.

  13. PRIMATE VISION • Stereoscopic vision and resultant depth perception allows primates to make accurate judgments about distance and position of adjoining tree limbs.

  14. EVOLUTION OF PRIMATES • Prosimians were the first type of primate to diverge from the ancestral primate line. • Surviving anthropoids are classified into three superfamilies. • New World monkeys • Old World monkeys • Hominoids

  15. New World Monkeys HOMINOIDS

  16. Primate Family Tree Crown lemur Orangutan

  17. Pre-Hominin Evolution • Ardipithecusramidus4.4 - ? mya • A. anamensis 4.2 - 3.9 • A. afarensis 4.2 - 2.5 • A. bahrelghazali 3.5 - 3.0 • A. africanus 3.5 - 2.5 • P. aethiopicus2.7 - 2.3 • A. garhi 2.5 - ? • P. boisei 2.3 - 1.3 • P. robustus 2.0 - 1.0 • Bipedalism • Tools • Language Reconstruction of Australopithecine

  18. Hominoid (Man/ Apes) Evolution • Proconsul is believed ancestral to hominins.

  19. Humans are hominoid

  20. Humans are hominins • Modern classification places the humans in the taxonomic group known as the tribe Hominini, that is humans are hominins. • It is only at this level of classification that humans are separated from all other great apes.

  21. Classifications can change • Prior to 1980 the accepted classification scheme identified humans as the only member of the family Hominidae. • The classification was based on comparative anatomy and physiology. • Molecular analysis has identified a much closer relationship between humans and other great apes.

  22. What is a hominin? • In the past the term ‘hominid’ referred to humans and their erect-walking ancestors. • Hominin is now the preferred term that refers to this group. • The only living hominin species is the modern human, Homo sapiens. • Hominins both living and extinct are distinguished by their ability to walk upright.

  23. Where did the human evolution begin? • In the 19th century fossils showed the origin was in Africa. See table 15.3 (pg 582).

  24. Time Distribution. • No fossil eveidence of hominins of the genus Homo before 2.4mya. • Fossils of hominins, such as Ardipithecus and Australopithecus appeared millions of years before Homo. • When the time distribution of one group occurs after that of the second group, the later group cannot be ancestral to the earlier group. • When the time distributions of two species coincide, they cannot have an ancestor-descendant relationship, eg. H.habilis and A.robustus.

  25. Australopithecus • Two forms of the genus: graciles and robusts. • Table 15.5 show the different species in the genus • Australopithecus. The robusts are placed by some scientists into another genus, Paranthropus. • This means that Australopithecus robustus is sometimes called Paranthropus robustus.

  26. Gracileaustralopiths • Several lines of evidence, including their jaw and teeth structure, support the conclusion that the graciles could be ancestral to the first Homo species.

  27. Robust australopiths • Robust australopithians have heavy built skulls, heavy brow ridges, very large molar teeth, and in males a bony crest on the top of the skull.

  28. Australopithecus vs. Modern Australopithecus, 4-3 myrs ago Modern human Chimpanzee

  29. Changes in the skull in the evolution of modern humans • Recognizable changes in the skull which occurred during the evolution of modern humans include: • Change in the arrangement of the teeth, from the rectangular arrangement of the apes to a parabolic shape in hominids, loss of the gap between front and back teeth. • Reduction in the size of the front teeth, especially the canines.

  30. Cranial Comparisons Homo ergaster H. neanderthalensis Homo Sapiens

  31. Cranial Comparisons • Loss of the large bony ridges (supraorbital ridges) above the eyes. • Larger brain size. • Flatter faces.

  32. Cranial Comparisons

  33. SEXUAL DIMORPHISM IN AUSTRALOPITHS • Sexual dimorphism - where differences exist between the adult males and females in average height, body mass, or other features.

  34. How did early hominins live? • Social organisation – group of related males who control and defend a group of females. • Inferring diets – relative size of teeth, microscopic examination of tooth wear, jaw size and jaw musculature. • Waistline – digestive tracts of herbivores are much longer than carnivores.

  35. How did early hominins live? • Habitat – examining fossils of plants and animals found in association with australopithecine fossils give us an idea what type of habitat was inferred. • Other evidence of habitat includes analysis of pollen. • Presence of water animals and plants indicate the presence of water.

  36. MODE OF LOCOMOTION • Although australopithecenes are capable of bipedal it would not be the same as humans today. • Also show adaptations to tree climbing. • The early hominins would have walked erect, however retreated to the trees at night. • Culture – basic tools used as well as sticks.

  37. Evolutionary relationships

  38. THE GENUS HOMO Early homo species were different : - reduction in size of teeth • increase in brain size. It is reasonable to hypothesise that increasing brain size resulted from natural selection favouring greater intelligence.

  39. The earliest human species is generally accepted as Homo habilis. • The genus Homo also includes H.erectus, H.heidlebergensis, H.neanderthalensis, and H.sapiens. • Scientists often disagree with the number of species, which is a reminder that even if they examine the same fossil material, scientists may differ in their interpretation and conclusions.

  40. CURRENT VIEW

  41. Fossil discoveries support a multi-branched human evolutionary line. Q. phyletic or branching evolution?

  42. About 10,000 to 12,000 years ago evidence of agricultural practices first appeared in the Middle East. • Nomadic lifestyles involved small groups of cooperative hunter-gatherers. • Sedentary lifestyles involved food production through domestication of animals and cultivation of wild plants. • Increased population size is related to a sedentary lifestyle.

  43. HUMAN BIOLOGICAL EVOLUTION • Biological Evolution describes the changes in human population that have resulted from natural selection acting over generations on inherited phenotypes and producing differential survival and reproduction under a particular set of environmental conditions.

  44. Genetic diversity exists in human populations, both discrete polymorphisms and clinal graduations. • Biological evolution, cultural change and technological evolution interact. • Cultural change in many ways is based on technological evolution. • Technology extends human capabilities.

  45. Cultural Evolution • With the appearance of Cro-Magnons, • human evolution has become almost entirely cultural rather than biological • Humans have spread throughout the world • by devising means to deal with a broad range of environmental conditions

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