Human Dawn Chap 1


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Human Dawn Chap 1

  1. 1. Chapter 1: Out of the Woods
  2. 2. Theory of Evolution <ul><li>Charles Darwin </li></ul><ul><li>19th century British scientist </li></ul><ul><li>Voyage of the Beagle: 1831-1836 </li></ul><ul><li>“On the Origin of Species by means of natural selection”: 1859 </li></ul>
  3. 3. Charles Darwin
  4. 4. H.M.S. Beagle
  5. 5. On the Origin of Species 1859
  6. 6. The Reaction to Darwin 1860
  7. 7. Darwin’s Argument for the Evolution of Species <ul><li>Observation # 1 </li></ul><ul><li>Most species produce far more offspring than could possible survive </li></ul><ul><li>Example: One pair of mice could produce about 40 babies a year and these babies could have their own offspring after only six weeks </li></ul><ul><li>Imagine what would happen if this process kept going indefinitely </li></ul>
  8. 8. Darwin’s Argument for the Evolution of Species <ul><li>Observation # 2 </li></ul><ul><li>An individual’s chances of survival will be affected by the environment in which it lives </li></ul><ul><li>Example: The environment includes the weather, finding food and a mate,finding somewhere to live and other animals and plants </li></ul>
  9. 9. Darwin’s Argument for the Evolution of Species <ul><li>Observation # 3 </li></ul><ul><li>Individuals vary. Some will be better adapted to their environment and will stand a better chance of surviving. </li></ul><ul><li>Darwin did not know what caused variation—we now know it is caused by mutations and the mixing up of genes during sexual reproduction. </li></ul>
  10. 10. Darwin’s Argument for the Evolution of Species <ul><li>Conclusion # 4 </li></ul><ul><li>If the better-adapted individuals survive long enough to reproduce … and if they pass the characteristics [genes] that helped them to survive on to their offspring. . . Their offspring will also stand a better chance of surviving. </li></ul><ul><li>This idea is sometimes called “the survival of the fittest” </li></ul>
  11. 11. What is a species? <ul><li>Is it just animals and plants that are “similar”? </li></ul><ul><li>How similar do they have to be? </li></ul><ul><li>Who decides? </li></ul><ul><li>How? </li></ul>
  12. 12. Are these animals from the same species?
  13. 13. Here is their offspring
  14. 14. So why aren’t horses and donkeys part of the same species? Because mules are not fertile!
  15. 15. How did the giraffe get such a long neck?
  16. 16. Lamark’s Answer: they stretched their necks to reach food: inheritance of acquired characteristics
  17. 17. Darwin’s Answer: giraffes with mutation for longer necks were able to reach food—>survived in greater numbers—>lived to reproduce and pass along their long-necked gene
  18. 18. Did Humans Evolve? <ul><li>Traditional religious answers spotlight human’s place at center or peak of creation </li></ul><ul><li>Modern scientific accounts focus on the emergence of all life forms as equally important: inter-relatedness of all life </li></ul><ul><li>Link </li></ul>
  19. 19. What is the subject and the source for the picture on p. 8-9? <ul><li>Australopithecus </li></ul><ul><li>scientific and artistic re-imagination and reconstruction of 5 million years ago </li></ul><ul><li>based on scientifically informed guess work </li></ul>
  20. 20. A real picture?
  21. 21. What are the Laetoli footprints? <ul><li>made by ancient human ancestors 3.5 million years ago </li></ul><ul><li>several hominids walking in a group made footprints in soft volcanic ash that were covered up, buried, preserved, and came to light </li></ul><ul><li>Link </li></ul>
  22. 22. Laetoli Footprints
  23. 23. Laetoli Footprints 2
  24. 24. Laetoli Footprints 3
  25. 25. Where were the footprints found? <ul><li>the lakebed of an ancient lake in northern Tanzania (East Africa) </li></ul>
  26. 28. What do they show us about our earliest ancestors? <ul><li>he/she was a two-legged mammal with upright posture—>&quot;bi-pedal” </li></ul><ul><li>Link </li></ul>
  27. 29. Bi-pedalism
  28. 30. Bi-pedalism 2
  29. 31. Who directed the team that found them? When? Where? <ul><li>Mary Leakey—>wife to husband Louis Leakey: British archaeologists </li></ul><ul><li>1976—> after more than 40 years of looking! </li></ul><ul><li>Tanzania </li></ul>
  30. 32. Why are teeth so commonly found among fossils? Why are they so important to archaeologists? <ul><li>teeth are the hardest material in human body—> enamel </li></ul><ul><li>slowest to decompose—>lasts much longer than the rest of the body </li></ul><ul><li>chewing marks on teeth indicate diet—>infer ecological niche, lifestyle, intelligence </li></ul>
  31. 33. By the way, what is a fossil? <ul><li>a mineral replica of a skeletal piece of an animal </li></ul>
  32. 34. Why are early human fossils rarer and more precious than diamonds? <ul><li>original population of early hominids was tiny compared to human population today </li></ul><ul><li>after death, corpses here usually displaced and devoured by larger predators and scavengers </li></ul><ul><li>if skeleton intact, it is usually decomposed (&quot;eaten&quot;) by microorganisms—>&quot;circle of life and death&quot; </li></ul><ul><li>if intact, it must be rapidly covered by protective sediment </li></ul><ul><li>if protected, it must be fossilized by mineral replacement of organic material </li></ul><ul><li>if fossilized, it must come to light and be discovered by someone who knows what it is! </li></ul>
  33. 35. How are fossils made? <ul><li>Link </li></ul>
  34. 36. What is the name of the species that made the Laetoli footprints? <ul><li>Australopithecus afaransis—> &quot;Southern ape of the afari people&quot; </li></ul>
  35. 37. Australopithecus afaransis
  36. 38. Australopithecus afaransis
  37. 39. When were the fossils originally made? How? <ul><li>3-4 million years ago </li></ul><ul><li>footprints made in soft volcanic ash and immediately covered </li></ul><ul><li>Link </li></ul>
  38. 40. What are three anatomical differences between apes and humans that make it possible for humans to walk upright? <ul><li>extended knee and hip joint allow straight leg walking, not ape waddling </li></ul><ul><li>center of gravity centralized under skull, not thrust forward as in apes </li></ul><ul><li>curved lower spine to support skull, not attached as in apes </li></ul><ul><li>parallel big toe, not opposable grasping toe, in order to distribute weight while walking </li></ul><ul><li>Link </li></ul>
  39. 41. The First Couple?
  40. 42. Why is the artist's picture on p. 16 controversial? <ul><li>sentimental pairing of male and female &quot;couple&quot; </li></ul><ul><li>more likely pair: mother and child </li></ul>
  41. 43. What is a hominid? <ul><li>member of human &quot;family&quot; of ancestors </li></ul><ul><li>walked upright </li></ul>
  42. 44. Why was bi-pedalism such a significant change in human history? <ul><li>frees forearms for carrying </li></ul><ul><li>tool-making </li></ul><ul><li>gesturing </li></ul><ul><li>intricate manipulations </li></ul><ul><li>ability to walk upright </li></ul><ul><li>large brains </li></ul><ul><li>Link </li></ul>
  43. 45. What are the three most significant unique human characteristics? <ul><li>ability to walk upright </li></ul><ul><li>large brains </li></ul><ul><li>ability to make tools </li></ul><ul><li>speech </li></ul>
  44. 46. Why did scientists used to think that larger brains were the first uniquely human characteristic? <ul><li>bigger brains precondition for higher intelligence </li></ul><ul><li>intelligence precondition for tool invention, making, and speech </li></ul>
  45. 47. Which of these three differences do scientists today believe emerged first? <ul><li>upright posture </li></ul><ul><li>but brain size remained unchanged for millions of years </li></ul>
  46. 48. What does the Latin term &quot;Homo sapiens&quot; mean? Who does it describe? <ul><li>&quot;man the wise, the intelligent&quot; </li></ul><ul><li>modern humans like us! </li></ul>
  47. 49. How large is the average adult brain? [No jokes, please!] <ul><li>Homo sapiens: 1200-1600 cc. </li></ul>
  48. 50. How large were the brains of Australopithecus afaransis? <ul><li>Australopithecus: 350-500 cc </li></ul>
  49. 51. Comparative brain sizes
  50. 52. What is the difference between tool using and tool making? What does either indicate about intelligence? <ul><li>improvisation or imitation vs. invention and planning </li></ul><ul><li>highly developed time sense for tool making </li></ul>
  51. 53. How long ago did the chimp line of evolution split from the human line? What is the evidence for this? <ul><li>5-6 million years ago </li></ul><ul><li>comparison of blood proteins and genes of chimps and humans </li></ul>
  52. 54. What is the &quot;foramen magnum&quot;? How does it differ in humans and apes? <ul><li>humans: entry of spinal chord in center of skull </li></ul><ul><li>chimps: entry further back in skull—>head thrust forward, not balanced—> limitation of size and weight </li></ul>
  53. 55. The foramen magnum
  54. 56. The foramen magnum compared
  55. 57. Brain size compared
  56. 58. Brains compared
  57. 59. What significance did this difference have for the direction of human evolution? <ul><li>brain growth depended on balance—>built-in limitation on brain-size of other apes </li></ul>
  58. 60. What percentage our DNA do humans share with chimps? <ul><li>98% of human and chimp DNA is identical—> chimps and gorillas share 97% </li></ul>
  59. 61. Why did upright posture have to precede the evolution of upright brains? <ul><li>larger brain size cannot be balanced or held up by ape posture—> neck and spine not able to support it </li></ul><ul><li>larger brain useless without free forelimbs to carry out instructions from brain </li></ul>
  60. 62. What was the most significant environmental change around 10-15 million years ago that favored apes with upright posture over more traditional apes? How did it do this &quot;favoring&quot; <ul><li>long term drought </li></ul><ul><li>reduced forests—>increased grasslands/savannah </li></ul><ul><li>predator/prey advantages and disadvantages of survival </li></ul>
  61. 63. What is the &quot;key process&quot; that drives evolution forward? <ul><li>changes in environment—>upsets settled patterns of survival of plants, animals, humans </li></ul><ul><li>constant process of mutation—> reproduction never perfect—>mutation supplies new variations that might be beneficial in dramatically new circumstances </li></ul>
  62. 64. What survival advantages did a more upright posture give those apes who had it? <ul><li>minimized skin exposure to harsh ultraviolet sunlight </li></ul><ul><li>cooled brains and conserved water </li></ul>
  63. 65. Are there other candidates for the title of &quot;our earliest human ancestor&quot;? Why don't we know for certain who the earliest actually is? <ul><li>Ardipethecus ramidus—> 4.4 million years old & Australopithecus anamensis—> 4.2 million years old </li></ul><ul><li>new fossil discoveries very likely—> ALL SCIENTIFIC KNOWLEDGE IS PROVISIONAL! </li></ul>
  64. 66. Why is the Great Rift Valley in East Africa such a great place to explore for early human fossils? <ul><li>Africa continent of origin </li></ul><ul><li>during prehistory it was a wet region that supported abundant plant & animal life </li></ul><ul><li>during our time it is a dry region where spring rains wash away surface sediment to expose the layers beneath </li></ul><ul><li>long-buried fossils are brought to light for those with the eyes to know what they are seeing </li></ul>
  65. 67. The Great Rift Valley
  66. 68. Name four of the best-known paleoanthropologists in the 20th century? <ul><li>Louis Leakey </li></ul><ul><li>Mary Leakey </li></ul><ul><li>Richard Leakey </li></ul><ul><li>Donald Johansen </li></ul>
  67. 69. Four Great Paleoanthropologists
  68. 70. What was the main staple of the Australopithecus diet? <ul><li>vegetarian—>roots, tubers, nuts, berries </li></ul><ul><li>occasional small rodents, lizards, insects </li></ul>
  69. 71. What was the probable key to the survival of Australopithecus against powerful, hungry predators? <ul><li>social nature </li></ul><ul><li>lived in groups of 20-30 </li></ul><ul><li>safety in numbers </li></ul>
  70. 72. Who is &quot;Lucy&quot;? Why is she such a significant archaeological find? <ul><li>she is the most complete skeleton of Australopithecus afaransis </li></ul><ul><li>&quot;Lucy In the Sky With Diamonds&quot; by Beatles playing on a cassette player the night she was discovered </li></ul><ul><li>Link </li></ul>
  71. 73. Why is the controversy about the fossilized bones of the &quot;first family&quot;? <ul><li>remains of 13 individuals—> 9 adults & 4 children </li></ul><ul><li>200 fragments </li></ul><ul><li>dramatic disparity between male and female height—> sexual di-morphism or separate species? </li></ul><ul><li>Link </li></ul>
  72. 74. How does Lucy's lower jawbone (mandible) show she is an evolutionary midpoint between the other apes and modern Homo sapiens? <ul><li>smaller jaw size indicates different diet </li></ul><ul><li>different diet indicates different lifestyle and ecological niche </li></ul>
  73. 75. The Change in Teeth
  74. 76. Change in Jaws