Traditional View of Human Evolution
human brain size and bipedality evolved together (as brain size increased, humans became more capable of walking on 2 legs). recent fossil findings show that the two may have not evolved together.
Australopithecus afarensis. skeleton very complete. contains mix of arboreal and bipedal characteristics.
walking on all four limbs. chimpanzees and great apes.
walking on two legs. developed among humans. walk with feet close together. can balance on one leg while the other swings forward.
3 Features of Bipedal footprints
1. Big toe is in line with the rest of the foot. (big toe is point of push off for human stride)
2. Distinct arch functions as shock absorber
3. distribution of weight from heel to toe. different from chimps (outside of foot)
found in 1976. 3 million years old. belonged to A. afarensis (only known hominid in the area). was most likely bipedal (big toe aligned with rest of foot) . beginning of an arch are clear. looks like 2 individuals were traveling together (2 sets of prints).
Chimp vs. Human Pelvis
chimp pelvis is much smaller. more flat/shallow pelvic inlet. longer coccyx (tail bone). chimp pelvis not holding anything up (quadrupedal).
Austropithecus aferensis/africanus pelvis
most resembles human pelvis, just smaller. shows it was probably bipedal.
"thigh" bone. longer femur means longer legs, makes walking more efficient.
"upper arm" bone. chimps (quadrupedals) have longer humerus in relation to femur. bipedals have shorter humerus in relation to femur.
humerus to femur ratio
higher in chimpanzees(0.89) and Lucy (0.87) than in Humans (0.75)
large opening in the base of the skull through which the spinal cord passes. in quadrupedal animals, foramen magnum is located at rear of skull. in bipedal animals, foramen magnum is centrally located.
foramen magnum of A. afarensis
location is intermediate between central and rear. most likely bipedal.
different lineages of humans split 800,000. Modern Africans are more closely related to ancient Africans than other modern humans.
out of africa theory.