Fossil Hominins: From Ardipithecus to Homo

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Traces the course of fossil hominin evolution from Ardipithecus to Presapient Homo

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Fossil Hominins: From Ardipithecus to Homo

  1. 1. Fossil Hominins From Ardipithecus to Homo
  2. 2. Fossil Hominins: General Trends Toward Homo Sapiens <ul><li>Large bulbous cranium </li></ul><ul><li>Short face compared to ape </li></ul><ul><li>Vertical carriage of head </li></ul><ul><li>Hands and Forelimbs Adapted to Tool Making and Use </li></ul><ul><li>Bipedal Structure of Postcranial Skeleton </li></ul>
  3. 3. Model of Human Evolution: Ardipithicus to Australopithecines <ul><li>Ardipithecus ramidus to Australopithecines </li></ul><ul><li>Australopithecus afarensis to A. africanus : Gracile Australopithecines </li></ul><ul><li>Paranthropus robustus and boisei: Robust Australopithecines—Dead end? </li></ul><ul><li>A. africanus to Homo habilis : Rise of tool manufacture? </li></ul>
  4. 4. Model of Human Evolution: Homo habilis to Sapients <ul><li>H. habilis to H. erectus: Global spread; increased tool assemblage </li></ul><ul><li>H. erectus to H. sapiens: Tool specialization and population explosion </li></ul><ul><li>H. neanderthalensis: Dead end? </li></ul><ul><li>Homo sapiens: (Future) End of the Line? </li></ul>
  5. 5. Fossil Trends: Encephalization (Cranial Capacity Increase) <ul><li>Ardipithecus ramidus: ca. 300-350 cc. </li></ul><ul><li>Australopithecus. afarensis: 390-500 cc; av. 440 cc </li></ul><ul><li>A. africanus: 435-530 cc; av. 450 cc </li></ul><ul><li>A./P robustus: 520 cc, one specimen </li></ul><ul><li>A.P. boisei: 500-530 cc; av. 515 cc. </li></ul>
  6. 6. Ardipithecus ramidis: The “Rooted Ground Floor Ape” <ul><li>Ardi: “Ground Floor” (Afar) </li></ul><ul><li>Rama: “Root” </li></ul><ul><li>Pithecus: “ape” </li></ul><ul><li>Date: 4.4 million years ago (mya) </li></ul><ul><li>Location: Middle Awash River Valley, NE Ethiopia </li></ul><ul><li>Size: 120 cm (4 ft.) </li></ul><ul><li>Weight (est.) 50 kg (110 lb.); heavier than Lucy </li></ul>
  7. 7. Ardipithecus ramidus: Reconstructed Features <ul><li>Cranial capacity: 300-350 cc. </li></ul><ul><li>Teeth: apelike with reduced canines; probably omnivore and/or fruit-eater </li></ul><ul><li>Significant prognathism (projection of lower face) </li></ul><ul><li>Feet: opposable toe with no arches </li></ul><ul><li>Quadrupedal in trees </li></ul><ul><li>Faculative biped on the ground: could walk short distances. </li></ul>
  8. 8. Ardipithecus Ramidus: Overview
  9. 9. Australopithecines and Homo: Overview
  10. 10. Homo habilis to Homo sapiens <ul><li>H. habilis: 500-800 cc; av. 680 cc. </li></ul><ul><li>H. erectus: 750-1250 cc; av. 1000 cc </li></ul><ul><li>Neanderthal: 1300-1750 cc. av: 1450 </li></ul><ul><li>H. (s.) sapiens: 900-2350 cc. av. 1400 </li></ul>
  11. 11. Fossil Trends: Forelimbs and Hands <ul><li>Shortened forelimb </li></ul><ul><li>Hands (manipulation, not locomotion) </li></ul><ul><li>Enlarged thumb </li></ul><ul><li>Straight, noncurved finger </li></ul><ul><li>Enhanced finger sensitivity </li></ul>
  12. 12. Fossil Hominins: General Trends--Bipedalism <ul><li>S-shaped vertebrae (backbone) </li></ul><ul><li>Short, wide, bowl-shaped pelvis </li></ul><ul><li>Femoral head (ball of femur at pelvis) angled and strengthened </li></ul><ul><li>Lengthened hindlimb </li></ul><ul><li>Angle of knee: femur “slopes” to pelvis </li></ul><ul><li>Platform (arched) structure of foot </li></ul><ul><li>Nonopposable big toe; toes not curved </li></ul>
  13. 13. Lucy ( Australopithecus afarensis ) and Us (Homo sapiens) <ul><li>Note the Following: </li></ul><ul><li>Shorter (3’6”) </li></ul><ul><li>Longer arms </li></ul><ul><li>Curved fingers </li></ul><ul><li>Shorter lower legs </li></ul><ul><li>Greater prognathism </li></ul><ul><li>Sloped forehead </li></ul><ul><li>Smaller cranial capacity </li></ul><ul><li>What are the Similarities? </li></ul><ul><li>Hint: it’s all related to bipedalism </li></ul>
  14. 14. Bipedalism: A. afarensis and H. sapiens compared, Fine Points
  15. 15. When We Became Bipedal (According to Gary Larson) <ul><li>“ Hey! Look! No hands!” </li></ul><ul><li>(Does he look like Lucy to you. . .?) </li></ul>
  16. 16. Gracile and Robust Australopithecines <ul><li>For A. africanus (top), note: </li></ul><ul><li>Somewhat rounder skull </li></ul><ul><li>No Sagittal crest </li></ul><ul><li>Prognathous jaw </li></ul><ul><li>For Paranthropus boisei, note: </li></ul><ul><li>Sagittal crest (ate a lot of veggies) </li></ul><ul><li>Massive lower jaw (mandible) </li></ul><ul><li>Flatter face </li></ul><ul><li>Massive cheek bones (zygomatic arch) </li></ul>
  17. 17. Summary of Australopithecines <ul><li>Cranial capacity increased marginally </li></ul><ul><li>All australopithecines had </li></ul><ul><li>Sloping foreheads </li></ul><ul><li>Prominent brow ridges </li></ul><ul><li>Prognathous lower face and jaws </li></ul><ul><li>Bipedal postcranial skeletons </li></ul><ul><li>Robust forms probably were dead ends </li></ul><ul><li>Graciles likely evolved toward Homo . </li></ul>
  18. 18. Australopithecus and Homo Compared—Frontal View <ul><li>Left: A. africanus </li></ul><ul><li>Right: H. habilis </li></ul><ul><li>Note: </li></ul><ul><li>Different Cranial Capacities </li></ul><ul><li>Brow Ridge Size </li></ul>
  19. 19. Australopithecus and Homo Compared—Side View <ul><li>Top: A. africanus </li></ul><ul><li>Bottom: H. habilis </li></ul><ul><li>Compare: </li></ul><ul><li>Mass of Jaws </li></ul><ul><li>Size of Crania </li></ul><ul><li>Prognathism </li></ul>
  20. 20. Postorbital Constriction <ul><li>Left: Homo erectus </li></ul><ul><li>Right: Australopithecus africanus </li></ul><ul><li>Note the narrower constriction of A. africanus’s postorbital constriction than that of H. erectus </li></ul>
  21. 21. Homo habilis: The First Known Toolmaker <ul><li>Note the following: </li></ul><ul><li>Face is much flatter </li></ul><ul><li>Reduced brow ridge (supraorbital torus) </li></ul><ul><li>Larger cranial capacity (680 cc.) </li></ul><ul><li>Toolmaking Technique </li></ul><ul><li>Hammerstone used to strike </li></ul><ul><li>A core (lump of stone) to knap </li></ul><ul><li>A Flake (stone chip) </li></ul><ul><li>Note: Stone has to be crystalline (so it will fracture predictably) </li></ul>
  22. 22. Homo habilis According to Gary Larson
  23. 23. Australopithecines and Homo Compared I <ul><li>Cranial capacity </li></ul><ul><li>Australopithecines: 400-530 cc </li></ul><ul><li>Homo: 500-2300 </li></ul><ul><li>Maximum braincase width </li></ul><ul><li>Australopithecines: low on skull </li></ul><ul><li>Homo: near top </li></ul><ul><li>Postorbital constriction Australopithecines: marked Homo: moderate to slight </li></ul>
  24. 24. Australopithecines and Homo Compared II <ul><li>Supraorbital torus (brow ridge) </li></ul><ul><li>Australopithecines: large to moderate </li></ul><ul><li>Homo: large to slight </li></ul><ul><li>Zygomatic arch </li></ul><ul><li>Australopithecines: large, flaring </li></ul><ul><li>Homo: small, not flaring </li></ul>
  25. 25. Australopithecines and Homo Compared III <ul><li>Facial size relative to brain case </li></ul><ul><li>Australopithecines: large </li></ul><ul><li>Homo: small </li></ul><ul><li>Jaw </li></ul><ul><li>A: Massive and prognathic; no chin </li></ul><ul><li>H: Not massive </li></ul><ul><li>Prognathism slight to nonexistent; </li></ul><ul><li>Chin present in sapients </li></ul><ul><li>Molars and premolars </li></ul><ul><li>Australopithecines: large; afarensis with diastema </li></ul><ul><li>Homo: small </li></ul>
  26. 26. Australopithecines and Homo Habilis Compared: Skulls <ul><li>General trends </li></ul><ul><li>Encephalization: Cranial capacity increases </li></ul><ul><li>Dentition: Cheek teeth are reduced </li></ul><ul><li>Sagittal Crest (where chewing muscles attach) </li></ul><ul><li>A./P. robustus and boisei: pronounced </li></ul><ul><li>A. africanus: sagittal keel or absent </li></ul><ul><li>H. habilis: absent </li></ul>
  27. 27. Australopithecines and Homo Habilis Compared: Skull/Face <ul><li>Braincase </li></ul><ul><li>A./P. robustus/boisei: less rounded </li></ul><ul><li>A. africanus: more rounded </li></ul><ul><li>H. habilis: most rounded of the three </li></ul><ul><li>Zygomatic arch </li></ul><ul><li>A./P. robustus/boisei: very pronounced </li></ul><ul><li>A. africanus: less pronounced </li></ul><ul><li>H. habilis: far less pronounced than the australopithecines </li></ul>
  28. 28. Homo habilis: Hands and Feet <ul><li>Hands </li></ul><ul><li>Curvature of finger bones are apelike, indicate powerful grip (arboreal) </li></ul><ul><li>Indications of greater manipulative skill </li></ul><ul><li>Larger blood supply to hand than earlier hominids </li></ul><ul><li>Evidence of greater nerve supply </li></ul><ul><li>Feet: existing fragments indicate modern form: </li></ul><ul><li>Remains lacked toes </li></ul>
  29. 29. Tool Traditions: Oldowan <ul><li>Named after Olduvai Gorge </li></ul><ul><li>Among the finds at Olduvai: </li></ul><ul><li>Side chopper, a core tool </li></ul><ul><li>Several flake tools, including </li></ul><ul><li>End scraper </li></ul><ul><li>Side scraper </li></ul><ul><li>Burin </li></ul><ul><li>Utilized flakes of unknown function </li></ul><ul><li>Belongs to Lower Paleolithic </li></ul>
  30. 30. Manufacturing Choppers <ul><li>Procedure </li></ul><ul><li>Knapper strikes a spherical piece of stone </li></ul><ul><li>Flake falls off opposite side </li></ul><ul><li>Tool flipped over and procedure repeated </li></ul><ul><li>Several blows create a cutting edge </li></ul><ul><li>Requirements reflect Intelligence </li></ul><ul><li>Planning and foreknowledge of design </li></ul><ul><li>Knowledge of breakage pattern of rock </li></ul><ul><li>Hand-eye coordination </li></ul>
  31. 31. Oldowan Tradition <ul><li>End chopper </li></ul><ul><li>Heavy duty scraper </li></ul><ul><li>Flake scraper </li></ul><ul><li>Spheroid Hammerstone </li></ul><ul><li>Chopper </li></ul><ul><li>Horn core tool or digger </li></ul>
  32. 32. Homo habilis and Homo erectus <ul><li>Compared to H. habilis, H erectus had: </li></ul><ul><li>Larger brain (1000 cc vs 680 cc average) </li></ul><ul><li>Forehead flatter, less sloping </li></ul><ul><li>More rounded occipital torus </li></ul><ul><li>endocasts indicate hemispheric asymmetry </li></ul><ul><li>Homo erectus and Homo sapiens </li></ul>
  33. 33. Homo erectus or ergaster <ul><li>Note: </li></ul><ul><li>Apelike but larger cranium </li></ul><ul><li>Postcranial Skeleton </li></ul><ul><li>Vertebrae: S Shaped </li></ul><ul><li>Ribcage: Not funnel shaped, now like ours </li></ul><ul><li>Pelvis: Bowl shaped </li></ul><ul><li>Angle of Thighbone </li></ul>
  34. 34. Homo erectus and Homo Sapiens: Cranium (Braincase) <ul><li>Forehead (Frontal) </li></ul><ul><li>H. erectus: sloping; low and flat </li></ul><ul><li>H. sapiens: vertical, indicating frontal lobe </li></ul><ul><li>Supraorbital torus (brow ridge) </li></ul><ul><li>H. erectus: prominent--extending as a bar </li></ul><ul><li>H. sapiens: slight or absent </li></ul><ul><li>Occipital torus: </li></ul><ul><li>H. erectus: present </li></ul><ul><li>H. sapiens: slight or absent </li></ul>
  35. 35. Homo erectus and Homo sapiens: Cranium and Face <ul><li>Sagittal keel </li></ul><ul><li>H. erectus: present; vestige of crest? </li></ul><ul><li>H. sapiens: slight or absent </li></ul><ul><li>Postorbital constriction </li></ul><ul><li>H. erectus: pronounced </li></ul><ul><li>H. sapiens: slight or nonexistent </li></ul>
  36. 36. Homo erectus and Homo sapiens: Facial Skeleton <ul><li>Facial skeletion </li></ul><ul><li>H. erectus: Relatively large, with large orbits and nasal opening </li></ul><ul><li>H. sapiens: Relatively small, with small orbits and nasal opening </li></ul><ul><li>Prognathism (jutting jaw) </li></ul><ul><li>H. erectus: Pronounced </li></ul><ul><li>H. sapiens: minimal or nonexistent </li></ul>
  37. 37. Homo erectus and Homo sapiens skulls <ul><li>Compare: </li></ul><ul><li>Brow ridges (supraorbital tori) </li></ul><ul><li>Prognathism </li></ul><ul><li>Constriction behind eye sockets (postorbital constriction) </li></ul><ul><li>Presence versus absence of chin </li></ul>
  38. 38. Tool Traditions: Acheulean <ul><li>Named after St. Acheul </li></ul><ul><li>Characteristics of Acheulean handaxe </li></ul><ul><li>Bifacial: both sides knapped </li></ul><ul><li>Symmetrical in breadth </li></ul><ul><li>Shaped to a point on one end </li></ul><ul><li>The edge is thin and sharp </li></ul><ul><li>Broad end is curved, but edge is still sharp </li></ul><ul><li>Part of Lower Paleolithic </li></ul>
  39. 39. Acheulean Axe as “Swiss Army Knife”; Abbevillean variation <ul><li>Swiss Army Rock? </li></ul><ul><li>Sharp tip: used for piercing </li></ul><ul><li>Thin edge: used for cutting (hide or meat off bone) </li></ul><ul><li>Broad end: used for chopping or scraping </li></ul><ul><li>Abbevillean Variation: </li></ul><ul><li>Bifacial, like the Acheulean </li></ul><ul><li>Not quite so symmetrical </li></ul><ul><li>Olduvai specimen: transitional type? </li></ul>
  40. 40. Manufacturing Acheulean Handaxes <ul><li>A demanding task </li></ul><ul><li>Symmetrical, finely shaped </li></ul><ul><li>Dozens of flakes removed, from 25 to 75 </li></ul><ul><li>Each flake blow must be precisely positioned </li></ul><ul><li>Core must be turned over again and again </li></ul><ul><li>to maintain symmetry </li></ul><ul><li>to keep edge straight </li></ul><ul><li>All the exterior rind ( cortex ) was removed </li></ul>
  41. 41. Abbevillian and Acheulean Handaxes <ul><li>Left: Abbevillian. Note asymmetry, rough retouch </li></ul><ul><li>Right: Acheulean. Note symmetry, fine retouch </li></ul>
  42. 42. Homo heidelbergensis or “Archaic” Homo sapiens <ul><li>Left: Skull. Note heavy brow ridge, prognathism </li></ul><ul><li>Right: Mandible. Note arc-like dental arcade, absence of diastema, absence of chin </li></ul>
  43. 43. Manufacturing Levallois Cores and Flakes <ul><li>Knappers </li></ul><ul><li>Draw outline of flake on stone module </li></ul><ul><li>Strikes flake of desired shape </li></ul><ul><li>Requires knowledge of breakage pattern of rock </li></ul><ul><li>Prepares rock beforehand to control how rock breaks when struck </li></ul><ul><li>Ensure right shape (e.g. cutting, perforation, piercing) is struck </li></ul>
  44. 44. Levallois Flake and Flaking Technique
  45. 45. Homo neanderthalensis : Skeleton <ul><li>Left: Homo neanderthalensis </li></ul><ul><li>Right : Homo sapiens </li></ul><ul><li>Compare </li></ul><ul><li>Relative thickness of bones </li></ul><ul><li>Breadth of ribcages </li></ul><ul><li>Size of skulls </li></ul>
  46. 46. Homo neanderthalensis: Cranium <ul><li>Left: H. neanderthalensis : note larger cranial size, occipital bun, prognathism, brow ridge </li></ul><ul><li>Right : H. sapiens : Note rounded cranium, presence of chin, absence of prognathism and brow ridge </li></ul>
  47. 47. Mousterian Tradition <ul><li>Positively identified with Neanderhals </li></ul><ul><li>Le Moustier, France is a Neanderthal site </li></ul><ul><li>Belongs to Middle Paleolithic </li></ul><ul><li>More sophisticated than Oldowan or Acheulean, both Lower Paleolithic </li></ul>
  48. 48. Mousterian Tool Assemblage <ul><li>Sample includes Scrapers, Points, and Handaxes </li></ul>
  49. 49. Upper Paleolithic: The Great Leap Forward? <ul><li>Probably begins about 50,000 BP </li></ul><ul><li>Primary Attributes </li></ul><ul><li>Shift from flake tools to blades </li></ul><ul><li>Subsistence on greater range of animal and plant species </li></ul><ul><li>Larger sites </li></ul><ul><li>Increase of bone, antler, ivory, shell, and other materials for tools </li></ul>
  50. 50. Upper Paleolithic: Associated Attributes <ul><li>Associated Attributes </li></ul><ul><li>Greater use of “imported” goods: </li></ul><ul><li>raw materials obtainable only from </li></ul><ul><li>great distances from inhabited sites </li></ul><ul><li>which suggests trade </li></ul><ul><li>More elaborate burials, with grave goods </li></ul><ul><li>Appearance and elaborate use of symbols and works of art. </li></ul>
  51. 51. Upper Paleolithic: The Blades <ul><li>Blades begin roughly 40,000 Years BP </li></ul><ul><li>Comparative efficiency </li></ul><ul><li>Levallois cores may produce 5 flakes </li></ul><ul><li>Many more blades could be produced from same core--and with longer cutting edge </li></ul><ul><li>Unlike other traditions, blade traditions are shorter lived </li></ul><ul><li>Oldowan: from ca.2.5 m. yrs BP </li></ul><ul><li>Acheulean: from ca 1.9 m. yrs BP </li></ul>
  52. 52. Upper Paleolithic Assemblage <ul><li>Upper Paleolithic Tools (left to right): biconical bone point, Perigordian flint blade, prismatic blade core, Soluterean Willow leaf point, double-row barbed harpoon point (various sites in France) </li></ul>
  53. 53. Homo florensiensis <ul><li>Small skull found in Liang Bua Cave, Flores Island, Indonesia, in 2004 </li></ul><ul><li>Other specimens found since then </li></ul><ul><li>Age range: 18,000 to 74,000 BP </li></ul><ul><li>Main attributes: rounded skull, chinless mandible, hominin postcranial skeletal parts </li></ul><ul><li>Fauna: Komodo dragons (large lizards), small elephantlike stegodons, and giant rats </li></ul><ul><li>Artifacts: Several small stone implements of sizes appropriate to H. florensis . </li></ul>
  54. 54. Homo Floresiensis: The Controversy <ul><li>Microcephalic human or separate species? </li></ul><ul><li>Same species: absence of thyroid gland essential to growth, other features similar to sapient form. </li></ul><ul><li>Different species: no chin, skull structure similar to H. erectus </li></ul><ul><li>Further debate: see pp. 314-315, Park text </li></ul><ul><li>Overall consensus: likely a separate species but not all share in that conclusion </li></ul>
  55. 55. To Sum Up: Representatives of Five Species <ul><li>The species: </li></ul><ul><li>1. Australopithecus afarensis </li></ul><ul><li>2. Australopithecus africanus </li></ul><ul><li>3. Homo habilis </li></ul><ul><li>4. Homo erectus </li></ul><ul><li>5. Homo neanderthalensis </li></ul>

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