Lecture 15.txt

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  1. Ardipithecus ramidus
    Discovered in Aramis, Ethiopia. came about approximately 5.6-4.4 mya. Discovered in forested area/negates the savanna hypotheses.

    • Derived Traits:
    • -less projecting and more "incisiform" canines
    • -non weight bearing elbow that may imply bipedalims
  2. Anatomical Changes associated with Bipedalism
    • 1. Curved spinal column brings body weight over feet
    • 2. Differently shaped pelvis helps position body weight and rearranges muscles
    • 3. Thigh bone (femur) angles inward & positions the knee at the mid-line of the body
    • 4. Bigger knee joints (body weight distributed on 2 instead of 4 legs).
    • 5. Non-grasping big toe in line w/the other toes -- ability to "toe off".
  3. Other Anatomical changes associated with Bipedalism
    • - Arch and ligaments act as a shock absorber when walking or running
    • - Bicondylar angle (angle of the femur), marker of bipedalism.
    • - Abductor muscles prevent waddling like a chimp and help you walk straight.
  4. Australopithecus afarensis (Lucy)
    • Founded in 1974 by Don Johanson and team.
    • Hominid dating from the Pliocene. She was the first definite biped found, but her brain was still modern day ape.
  5. How old is Lucy?
    • - Ash solidifies and forms rocks that are high in potassium(K) - the hot lava boils out all the argon(no argon in fresh rock).
    • - The only argon present must be from the decay of potassium(K), which occurs at a constant rate.
    • - the amount of argon present in volcanic rock associated w/the fossil layer allows us to assign a date to the fossil.
    • - THUS.. Potassium Argon Dating places Lucy at about 3.2 myo.
  6. Australopithecus afarensis was bipedal:
    • -angled femur
    • -knee surface flattened and broadened for stability
    • -pelvic blade shortened
    • -big toe convergent

    BUT.. not exactly like modern human. Lucy still had short legs, and long curved fingers and toes, and a conical chest.
  7. Australopithecus afarensis teeth...
    are intermediate between apes and humans in several ways:

    • - the canines of A. afarensis show wear on the sides(like a chimp) and on the tip(like a human).
    • - diastema is intermediate between ape and human.
    • - dental arcade is more ape like.
  8. Australopithecus afarensis skull...
    shows Ancestral Traits such as:

    • - strong prognathism
    • - small sagittal crest
  9. in short A. afarensis illustrates...
    • A mosaic nature of hominin evolution:
    • Head of an ape, Body of a person.
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Lecture 15.txt
Early Hominid
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