Lecture 15.txt

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

• 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".

• - 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.

• 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.

• - 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.

• -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.

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.

shows Ancestral Traits such as:

• - strong prognathism
• - small sagittal crest

• A mosaic nature of hominin evolution:
• Head of an ape, Body of a person.