Arch 270 Week 8

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  1. Adaptations to Hominid Bipedal Walking (basic list)
    • 1) forward placed foramen magnum
    • 2) sigmoid or S curved vertebral column
    • 3) increased capacity for lumbar lordosis in females
    • 4) short, broad posteriorly tilted pelvis
    • 5) elongation of lower limb (femur particularly)
    • 6) angled medially femur (allows knee to lie in midline of body, has larger medial condyle)
    • 7) strong abductor muscles 
    • 8) locking knee
    • 9) enlarged and aligned big toe
    • 10) arched foot to act like spring
  2. Forward placed foramen magnum
    -centers the cranium over the vertebral column, allows maintenance of erect posture
  3. Sigmoid Curved vertebral column
    • -also comes with narrower ribcage
    • -centers weight over pelvis 
    • -4 curves
    • -2 primary (present at birth)
    • -2 secondary (develop as infants/toddlers as we become bipedal)
    • -anterior curves
    • --cervical(secondary)
    • --lumbar(primary)

    • -posterior curves
    • --thoracic(secondary)
    • --pelvic/sacral(primary)
  4. Lumbar Lordosis
    • -allows lumbar vertebrae to become more dorsally wedged in females when pregnant
    • -surface are of vertebral facets are about 14% larger in females
    • -superior articular facets are oriented more coronally to resist fetal load
  5. Short Broad pelvis
    • -posteriorly tilted pelvis
    • -particularly the ilium 
    • -supports weight better 
    • -allows vertical orientation of trunk
    • -anchors pelvic and leg muscles
  6. Abductor Muscles
    • -gluteus minimus and gluteus medius 
    • -used to counteract the inward torque of the torso when supporting body weight on one leg
  7. Locking Knee
    -allows full joint extension and better GAIT
  8. Enlarged Hallux
    • -enables foot to completely support body weight 
    • -loss of pedal prehension, still ape foot
  9. Bipedal running (list of adaptations)
    • -endurance runners (uncommon amongst quadrupedal animals)
    • 1) long spring like tendons
    • 2) long legs relative to body mass
    • 3) larger joint surfaces
    • 4) enlarged gluteus maximus
    • 5) long and narrow waist
    • 6) free rotation of head compared to chest
    • 7) wide shoulders
    • 8) occipital projection for muscle attachment
    • 9) obligate oral breathing
    • 10) effective sweating
  10. Tendons for running
    • -long and spring like
    • -short muscle fascicles save up to 50% of metabolic cost of running
    • -ex achilles tendon first found in Homo erectus
  11. Where are longer legs for running first found
    -Homo erectus
  12. Joint surface enlargement
    • -specific for running
    • -Homo have larger lower joint surfaces
  13. Enlarged gluteus maximus
    • -adaptation for running
    • -first true buttocks
    • -not engaged when walking, only when running
    • -stabilizes the trunk on planted foot and to decelerate leg swing on other foot
  14. Elongated and narrow waist
    • -allows counter rotation of hips compared to trunk
    • -fully developed in Homo erectus, partially found in australopithecines
  15. Independent head movement
    • -allows you to keep your head on straight as the rest of your torso rotates to counteract the rotation of your hips
    • -fully developed in homo erecuts
  16. Wide shoulders
    • -enhancement for running
    • -allows swinging of arms to counter rotate the hips
    • -characteristic of Homo
  17. Theories for Bipedal evolution
    • -carrying model- began because we needed to transport scarce resources
    • -vigilance model- stand up to see predators
    • -heat stress model-decrease surface area facing sun
    • -energy efficiency model- we are more efficient bipedally than chimps at 4 legs
    • -foraging/harvest model-stand up to reach stuff in trees
    • -display model-to assert intimidation for predators or sexual needs
  18. Adaptations for hominid language
    • -hemispheric specialization of the brain (left for language and symbol use)
    • -broca's area- speech production (present in australopithecines)
    • -wernickes area- language comprehension (homo habilis)
    • -enlarged thoracic vertebral canal(more control over breathing, neanderthals)
    • -flexed basicranium- bends and lengthens the pharynx, lowers the larynx allows broad range of sounds(H erectus)
  19. Increasing Hominid Brain Size
    • -increasing size and complexity starting with Homo
    • -slower infant maturation(high parental investment)
    • -transmission of culture
    • -tool use and manufacture
    • -increasing social complexity
    • -resource distribution
    • -environmental challenges
  20. Hominid Dentition
    • -obviously changing dental formulas
    • -wider and more parabolic dental arcades
    • -thicker enamel (compared to quadrupedal apes)
    • -reduced canines with no/smaller diastema
    • -larger posterior and smaller anterior teeth
  21. Neoteny
    • -where adults of a species retain a trait that was only previously found in the juvenile forms
    • -adult human foramen magnum placement similar to juvenile chimps placement, but adult chimps is much farther back
  22. 2 Different Skeletal Classification
    • -cranial vs postcranial
    • -axial vs appendicular
  23. Two types of bone tissue
    • -compact or cortical bone
    • -cancellous, trabecular or spongy bone
  24. Cortical Bone
    • -compact bone
    • -hard, dense external layer of bone
    • -bulk of long bone shafts
  25. Cancellous Bone
    • -trabecular or spongy bone
    • -20% of skeletons mass, but 10x surface area
    • -inner lattice work of branching bony spicules provide strength without mass
  26. Obligate Behaviours of hominids
    • -bipedal locomotion (which came about millions of years before an increase in brain size)
    • -non honing chewing
  27. Textbook Bipedal Hypotheses
    • -patchy forest-had to move long distances with no trees so it came about easily
    • -provisioning-males needed to carry food to females so they could care for more infants at a time
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Arch 270 Week 8
2013-11-30 21:11:41

Arch 270 week 8
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