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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
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".
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.
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.
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.
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.
Australopithecus afarensis teeth...
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.
Australopithecus afarensis skull...
shows Ancestral Traits such as:
- - strong prognathism
- - small sagittal crest
in short A. afarensis illustrates...
- A mosaic nature of hominin evolution:
- Head of an ape, Body of a person.