Fossilization
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Only occurs under precise set of conditions: Step One: Bones buried in sediment (sand, mud, silt, gravel) Step Two: Minerals from water & soils replace protein material in the bones & transform the bone into stone, preserving its form

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Fossilization

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Only occurs under precise set of conditions:

Step One: Bones buried in sediment (sand, mud, silt, gravel)

Step Two: Minerals from water & soils replace protein material in the bones & transform the bone into stone, preserving its form

Step Three: Erosion, natural movement of land exposes fossils

Step Four: Discovery

Fossilization


  • Fragmentary – bits & pieces of the skeleton; less than 50 complete hominid skeletons

  • Over-representation of certain bones:

    • Teeth, mandible (lower jaw), and bones of the pelvis are most likely to be preserved (most durable bones of the skeleton)

  • Biases in interpretation

Biases in Fossil Record


What kind of bones are they? (Part of the skull or part of the post-cranial skeleton?)

Human or some other primate?

Male or female?

Age at time of death? (age of individual)

Age of bones themselves

Context in which bones were found

Questions about Fossil Remains


First trait to have developed that distinguishes humans from other primates is BIPEDALISM

Human or non-human remains


  • Centralized foramen magnum (hole at base of skull through which spine enters)

  • S-shaped curvature in spine

  • Rounded, short, bowl-shaped pelvis

  • Relative Limb Proportions: Longer, thicker, more developed leg bones than arm bones

  • Femur angles inward toward the knee

  • Big toe parallel to other toes

  • Arch in foot bones

Skeletal Evidence for Bipedalism


AnatomY OF BIPEDALisM


Scientists look for specific clues in the skeleton

Focus is on pelvis & skull

MALE OR FEMALE?


Male pelvis is narrower; illia are not as splayed; arch in front is V shaped

Female pelvis is wider, more robust, illia splay outward, arch in front U shaped

Differences in the pelvis


Male cranium is generally bigger Female cranium:

has a square chin; rounded chin;

less angle to jaw;sharper angle to jaw;

larger mastoid bone;smaller mastoid bone;

small bump at back;no bump at back;

more sloping forehead;more bulging forehead;

heavier browridgesfainter browridges

Differences in the skull


  • Can obtain lots of information from teeth

  • What types of food were consumed

    • How they interacted with environment to acquire food

      For example, the patterns of wear on the teeth suggest a diet of hard food items such as nuts, seeds and roots requiring lots of chewing and grinding

Clues from Teeth


  • Age of bones/fossils

    • Important to place in evolutionary time frame

    • Many scientific methods to determine age

  • Forensic information – What can we learn about the individual?

    • Stature

    • Age at time of death

    • Diseases or injuries evident

    • Strenuous physical activity

  • This information is important to reconstruct the variation in the population and the way of life of the individual

Other important information


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