Card Set Information
Discovered in Aramis, Ethiopia. came about approximately 5.6-4.4 mya. Discovered in forested area/negates the savanna hypotheses.
-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.
-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.
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).
is intermediate between ape and human.
- dental arcade is more ape like.
shows Ancestral Traits such as:
A mosaic nature of hominin evolution:
Head of an ape, Body of a person.