Our Fossil Ancestors


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Covers the principles of natural selection and genetic mutation; reviews the biological evolution of fossil hominins; examines the tools made by Homo habilis through modern humans

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Our Fossil Ancestors

  1. 1. Our Fossil Ancestors How We Got to Be We
  2. 2. How We Became the Way We Are <ul><li>We’ve looked at our own anatomy and those of our closest relatives, the chimps </li></ul><ul><li>With the evidence of our ancestors in scattered pieces, we need to reassemble the existing parts </li></ul><ul><li>We also need to infer the missing parts based on our knowledge of human anatomy </li></ul><ul><li>We start with the principles of natural selection and genetics, the two primary sources of human evolution </li></ul>
  3. 3. Overview of Human Evolution <ul><li>Principles of evolution: Natural selection and genetics </li></ul><ul><li>Taxonomy </li></ul><ul><li>The behavior of our primate cousins </li></ul><ul><li>Our ancestry from Australopithecus to Homo </li></ul><ul><li>Tools as evidence of culture evolution </li></ul><ul><li>Capacity for Language—and thereby capacity for culture </li></ul>
  4. 4. Principles of Evolution: Natural Selection <ul><li>Darwin’s Contribution: On the Origins of Species </li></ul><ul><li>Natural Selection: A twofold process </li></ul><ul><li>First, there is a wide variety of species that come into being. </li></ul><ul><li>Second, environmental factors select those species that are better adapted to the conditions than others </li></ul><ul><li>Example: “Industrial melanism” among moths in England </li></ul>
  5. 5. “ Industrial Melanism”: An Example of Natural Selection <ul><li>Coal-burning steel plants spread soot all over the city, such as Manchester, England </li></ul><ul><li>Birds picked off the light colored moths and left the dark colored ones </li></ul><ul><li>Result: dark colored moths enjoyed a selective advantage—can you see why in this photo? </li></ul><ul><li>In rural areas, the light colored moth had the selective advantage—no soot. </li></ul><ul><li>This process is known as “industrial melanism”—melanism means “being dark” </li></ul>
  6. 6. Principles of Evolution: Genetics I <ul><li>If natural selection involves the varieties of species to be selected from, then where do the varieties originate in the first place? </li></ul><ul><li>The real origin of species rests in the genes of all life forms—plants, animals, fungi </li></ul><ul><li>Gregor Mendel, an Augustine monk, experimented with peas to discover the effects of combining different strains </li></ul><ul><li>These efforts started the science of genetics </li></ul>
  7. 7. Principles of Evolution: Genetics II <ul><li>The nucleus (center) of a cell contains all genetic material: genes, chromosomes, and DNA </li></ul><ul><li>Genes : Hereditary information determining physical characteristics </li></ul><ul><li>Chromosomes : the chains containing chromosomes </li></ul><ul><li>DNA (deoxyribonucleic acid): the molecules that make up most of the chomosomes </li></ul><ul><li>DNA contains 2 chains linked by the bases adenine (A), thymine (T), cytosine (C), and guanine (G) </li></ul><ul><li>A always matches with T, and C always matches with G </li></ul>
  8. 8. Principles of Evolution: Genetics III <ul><li>Genotype: the genetic makeup of a particular characteristic (peas, eye color) </li></ul><ul><li>Phenotype: the physical characteristics created by the genetic makeup </li></ul><ul><li>Genes are always paired: male contributes half, female contributes half </li></ul><ul><li>Alleles : Variations of a genetic characteristic </li></ul><ul><li>These are chains of DNA </li></ul>
  9. 9. Principles of Evolution: Genetics IV <ul><li>When different alleles combine: </li></ul><ul><li>Allele of one manifests as a phenotype (Dominant; all peas are smooth in the upper diagram) </li></ul><ul><li>The other does not (Recessive, wrinkled peas) </li></ul><ul><li>Only in the second generation do wrinkled peas appear as phenotypes because two genes for wrinkled peas are combined </li></ul><ul><li>Or both alleles may manifest as hybrid (Codominant, color of flowers in lower left—red and white are combined to produce pink) </li></ul>
  10. 10. Principles of Evolution: Genetics V <ul><li>The origin of species: mutation or change in genetic makeup </li></ul><ul><li>DNA molecules may switch positions on the chain or cross over into the opposite chain to produce a new characteristic or trait . </li></ul><ul><li>Whether the new trait survives depends on how well it adapts to the environment—the natural selection process </li></ul><ul><li>This is the natural history of our earliest hominin forms </li></ul>
  11. 11. Human and Prehuman Populations: Evolutionary Processes <ul><li>Early hominins are products of both mutation and natural selection. </li></ul><ul><li>To the biological we can add a third factor: culture. </li></ul><ul><li>Changes and natural selection can be modified to explain the selective advantages that culture has </li></ul><ul><li>Culture involved adaptation to habitats: a cold habitat proved advantageous to so-called Eskimos; a warm habitat such as a tropical rainforest fit the Amazonian native population well </li></ul><ul><li>This section looks at both biological and cultural factors supporting the early hominins </li></ul>
  12. 12. Major Developments in Early Hominins: Biology <ul><li>Australopithecus afarensis: The first evidence of hominin bipedalism; included “Lucy” and this couple in Laetoli who left footprints characteristic of human bipeds </li></ul><ul><li>Australopithecus africanus: Gracile (light-boned) hominins who probably were among our ancestors; other varieties have been found and described. </li></ul><ul><li>Paranthropus boisei and robustus: the robust (heavy boned) hominins with powerful jaws to chew tough vegetation—most likely died off without progeny </li></ul>
  13. 13. Major Developments in Early Hominins: Culture <ul><li>Homo erectus: The first maker of handaxes (Acheulean tradition) and users of fire (upper right) </li></ul><ul><li>Homo habilis: The first documented toolmaker, of choppers (Oldowan tradition, upper left) </li></ul><ul><li>Homo heidelbergensis: The first maker of flakes from prepared cores </li></ul><ul><li>Homo neanderthalensis: Maker of two complex tool traditions: Mousterian and Chattelperronnian </li></ul><ul><li>Lower left and right) Two very different artist conceptions of “neanderthals ” </li></ul>
  14. 14. Trends of the Earliest Hominins: The Australopithecines <ul><li>The next several diagrams will show the following: </li></ul><ul><li>Bipedalism was fully established with Australopithecus afarensis and africanus </li></ul><ul><li>Paranthropus boisei and robustus were fully bipedal </li></ul><ul><li>All australopithecines (including Paranthropus) had apelike facial features; the robust also had a sagittal crest for their chewing muscles </li></ul><ul><li>They also had long arms, curved fingers, short tibia (look up your diagram) and other apelike traits </li></ul><ul><li>Their cranial capacities were small, not much larger than apes (see next slide) </li></ul>
  15. 15. Encephalization (a.k.a. Bigger Brains) <ul><li>A. 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><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>
  16. 16. 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>
  17. 17. 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>
  18. 18. 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>
  19. 19. Genus Homo: Biological and Cultural Trends <ul><li>With Homo habilis, some of the apelike traits begin to disappear </li></ul><ul><li>Prognathism and heavy brow ridges begin to be reduced </li></ul><ul><li>Arms are long in H. habilis but shorter in H. erectus </li></ul><ul><li>Encephalization increases from 680 cc in H. habilis to 1000 cc in H erectus and upward from there. </li></ul><ul><li>Tool design, manufacture, and use define the genus Homo from the australopithecines </li></ul>
  20. 20. A Primer on Stone Tools <ul><li>Stone tools have to be made of crystalline rock : otherwise they won’t fracture </li></ul><ul><li>Examples include obsidian and flint, like these arrowheads </li></ul><ul><li>The main types of stone tools are cores , the rock being worked on, and flakes, the pieces chipped off the core (lower left) </li></ul><ul><li>Flakes include blades , which are at least twice as long as they are wide (lower right) </li></ul>
  21. 21. A Primer on Stone Tool Manufacture <ul><li>A hammerstone is the stone used to flake chips of stone from the core in the toolmaking process (top) </li></ul><ul><li>The percussion technique involves the use of stone or softer material to strike the stone being worked </li></ul><ul><li>The hard hammer percussion technique involves striking the stone with the hammerstone, mostly for rough work. (top) </li></ul><ul><li>The soft hammer percussion technique is the use of antler, bone, wood, or ivory for retouching the work using percussion methods </li></ul><ul><li>The pressure technique involves pressing the work using soft material such as an antler for retouching; here, the toolmaker is using bone to refine an obsidian projectile point. </li></ul>
  22. 22. 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 f lake (stone chip) </li></ul><ul><li>Note: Stone has to be crystalline (so it will fracture predictably) </li></ul><ul><li>This is the Oldowan tradition </li></ul>
  23. 23. Homo erectus: Cranial Structure <ul><li>Note the Following: </li></ul><ul><li>Cranial capacity: 1,000 cc </li></ul><ul><li>Occipital bun </li></ul><ul><li>Reduced brow ridge </li></ul><ul><li>Reduced sloping forehead </li></ul><ul><li>Reduced prognathism </li></ul><ul><li>Artist’s conception of H. erectus </li></ul>
  24. 24. Homo Erectus (H. ergaster to Some): Postcranial Skeleton <ul><li>Note the following: </li></ul><ul><li>Fully bipedal </li></ul><ul><li>Arms about length of Homo sapiens </li></ul><ul><li>Cranial capacity: 1000 cc (average) </li></ul><ul><li>Main apelike features: </li></ul><ul><li>Prognathous lower face </li></ul><ul><li>Sloping forehead </li></ul>
  25. 25. Tool Traditions: Lower Paleolithic <ul><li>This is the longest period of tool making, starting at about 1.5 million years ago with the Oldowan </li></ul><ul><li>The Acheulean makes its appearance about one million years ago </li></ul><ul><li>The handaxe style is not found east of Central India; this boundary is the Movius Line, named after Hallam Movius, who first made that observation. </li></ul>
  26. 26. Lower Paleolithic <ul><li>Oldowan Tradition: </li></ul><ul><li>Four or five strokes </li></ul><ul><li>Unspecialized: choppers </li></ul><ul><li>Flakes also made and used </li></ul><ul><li>Acheulean Tradition: </li></ul><ul><li>50-75 strokes </li></ul><ul><li>Symmetrical design </li></ul><ul><li>Multiple uses: cutting, piercing, chopping </li></ul>
  27. 27. Homo heidelbergensis (a.k.a. “Archaic” Homo sapiens <ul><li>Note the following: </li></ul><ul><li>Brow ridges much reduced </li></ul><ul><li>Forehead is higher, though sloping </li></ul><ul><li>Reduced prognathiam </li></ul><ul><li>Cranial capancity 1200 cc. </li></ul><ul><li>Artist’s conception shows closer similarities to ourselves </li></ul>
  28. 28. Manufacturing Levallois Cores and Flakes <ul><li>Knappers: </li></ul><ul><li>Selects the appropriate core, up to a pound of stone </li></ul><ul><li>Strikes the edge of the core </li></ul><ul><li>Knaps the surface of the intended flake </li></ul><ul><li>Knocks off the flake </li></ul><ul><li>Retouches the flake to desired shape </li></ul><ul><li>May knap four to five flakes </li></ul>
  29. 29. Homo neanderthalensis and H. sapiens skull <ul><li>Note the following for “Classic” Neanderthal </li></ul><ul><li>Greater prognathism; humans lower jaw is straight </li></ul><ul><li>Absence of chin that human has </li></ul><ul><li>Presence of brow ridge; human has none, has higher forehead </li></ul><ul><li>Presence of occipital bun </li></ul><ul><li>Larger cranial capacity: 1450 cc vs. 1400 cc in humans </li></ul><ul><li>Also note: Artist’s conception of Neanderthal child </li></ul>
  30. 30. Homo neanderthalensis and H. sapiens : Postcranial Skeletons <ul><li>Note the following for Neanderthals: </li></ul><ul><li>Heavier brow ridge and sloping forehead </li></ul><ul><li>Bones generally more robust </li></ul><ul><li>Larger rib cage </li></ul><ul><li>Broader pelvis </li></ul><ul><li>Shorter forearm </li></ul><ul><li>Shorter tibia </li></ul><ul><li>Larger ankle joint </li></ul>
  31. 31. Middle Paleolithic <ul><li>Tools begin to show greater specialization </li></ul><ul><li>With the Levalloisian tradition, flake tools are more important than core tools like the Acheulean </li></ul><ul><li>The Mousterian tradition, associated with Neanderthals, become more specialized, dominated by notches, scrapers, and points </li></ul>
  32. 32. Levalloisian Tradition <ul><li>This tool involves a unique technique, as follows: </li></ul>
  33. 33. Neanderthal Tools: Mousterian and Châtelperronian Traditions <ul><li>Mousterian (top) </li></ul><ul><li>Bordes: 63 types </li></ul><ul><li>Burins (engravers) </li></ul><ul><li>Scrapers and knives </li></ul><ul><li>Even a type of handaxe </li></ul><ul><li>Part of the Mesolithic </li></ul><ul><li>Châtelperronian (bottom) </li></ul><ul><li>First blades—by Neanderthals </li></ul><ul><li>Definition: flakes twice as wide as they are long </li></ul><ul><li>Initiated the Upper Paleolithic </li></ul>
  34. 34. Upper Paleolithic <ul><li>Except for the Chatelperronnian, tools of the Upper Paleolithic are products of Homo sapiens </li></ul><ul><li>This period begins about 35,000 BP and works up to the near present; Aztecs still used obsidian tools at the time of Conquest </li></ul><ul><li>The tools increase in specialization, vary by region, and become smaller and more refined </li></ul><ul><li>Artwork and ornamentation also become evident </li></ul>
  35. 35. Upper Paleolithic: Modern Human Tool Traditions . <ul><li>Commonalities of Tools: </li></ul><ul><li>Blades: Ever thinner and smaller </li></ul><ul><li>Increased tool specialization </li></ul><ul><li>Other material: bone, ivory, antler </li></ul><ul><li>Other Developments </li></ul><ul><li>Artwork (such as this mural at Altamira, Spain) </li></ul><ul><li>Ornamentation (Venus statuettes) </li></ul><ul><li>Except for the Chatelperronian, the </li></ul>
  36. 36. Review and Conclusion <ul><li>We have. . . </li></ul><ul><li>Looked at the biological bases of culture: for language, toolmaking, and bipedalism </li></ul><ul><li>Compared our anatomy with chimps, our closest relatives </li></ul><ul><li>Discussed evolutionary change based on natural selection and mutation </li></ul><ul><li>Looked at our ancestors and the tools they made </li></ul>
  37. 37. The Territory Ahead <ul><li>Nonhuman Primate Behavior: How close in behavior are our cousins’ to our own? </li></ul><ul><li>Language: The medium of culture </li></ul><ul><li>Making a Living: Industrial societies are not the only cultures in the world </li></ul><ul><li>Sex, Family, and Its Extensions: The world’s first social organizations </li></ul><ul><li>Economics: How goods and services are provided </li></ul><ul><li>Social Control: Governance and law </li></ul><ul><li>Psychology: Freud didn’t start it all </li></ul><ul><li>The Supernatural: Were there gods before God? </li></ul><ul><li>Culture Change and Globalization: Is there life outside corporations? </li></ul>