ANTH151 Lecture Notes - Lecture 4: Australopithecus, Paleontology, Australopithecine
10 May 2018
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ANTH151 Lecture
IV: Bipedalism: Why walk on two feet?
Lucy (Australopithecus afarensis)
• Theorists of human evolution assumed early human-like creatures would
• ‘Lucy’ discovered in Hagar, Ethiopia by Donald Johanson 1974
• Approximately 40% complete
• 107cm tall and 28kg when alive
• Probably 25-30 years old; most likely female
• Dated to 3.5mya
• Human-like traits
• Large grinding molars
• Bipedal
• Ape-like traits
• Sharp canines
• Long arms
• Sexual dimorphism
• Brain size and shape
• Adapted to coarse-food diet, dependent young and possible polygyny
Classification issues
• Lumpers v splitters
• How different should a specimens be to justify a new species? (Incentives for naming)
• Relations among exist species difficult to determine (genetic evidence not available)
• Species may have been variable at certain points in time (stabilising selection over time)
Hominid genealogy less a ‘tree’ than a bush, with many branches that died out
Recall that Miocene (25-5mya) was period of great diversity in apes
Today we focus on Australopithecus and Parathropus
Evidence in skull for bipedalism
• Location of foramen magnum suggests whether spine was vertical
Legs elongated
• Increasing stride length improves efficiency
• Stride lengths when we accelerate to run (more than just increased cadence)
Major anatomical changes
• Skull: position of a foramen magnum
• Spine: distinctive double curves
• Hips: bowl-shaped pelvis and ilium in short and broad
• Knees: turn in and valgus angle
• Feet: hallux (big toe) also adducted
Why is this significant?
• Bipedalism preceded other major innovations of our genus, such as large brain, tool making,
or social advances
• Bipedalism may not have been gained by Australopithecines, but retained from earlier suite of
arboreal adaptations
Disadvantages to bipedalism
• Climbing more difficult without grasping foot
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Document Summary
Hominid genealogy less a tree" than a bush, with many branches that died out. Recall that miocene (25-5mya) was period of great diversity in apes. Evidence in skull for bipedalism: location of foramen magnum suggests whether spine was vertical. Increasing stride length improves efficiency: stride lengths when we accelerate to run (more than just increased cadence) Major anatomical changes: skull: position of a foramen magnum, spine: distinctive double curves, hips: bowl-shaped pelvis and ilium in short and broad, knees: turn in and valgus angle, feet: hallux (big toe) also adducted. Why is this significant: bipedalism preceded other major innovations of our genus, such as large brain, tool making, or social advances, bipedalism may not have been gained by australopithecines, but retained from earlier suite of arboreal adaptations. Well-adapted to bipedalism: slipped disc, obstetric problems, hernias, varicose veins, fallen arches, bunions and calluses, sprained ankles, loss of leg catastrophic for walking.
