Evolution of bipedalism part 2 Flashcards
What is the shape of vertebral columns in humans, what are its components and their function:
- Vertebral column is positioned vertically has distinct S shape, formed by primary, thoracic, sacral, and opposite secondary curvatures, in cervical and lumbar regions.
- Biped must balance on one leg, while lifting other foot of ground, thus secondary curvatures help bring centre of trunks mass anteriorly, closer to body’s midline and above feet.
What is the shape of vertebral columns in quadrupedal, what is it composed of, and what is its function?
Vertebral column of a quadrupedal (such as chimpanzee or guerrillas) show a C-shape, which is composed by thoracic and sacral curvatures. Vertebral column helps bring central gravity right through their back to ground, balancing weight over four limbs.
What must a chimpanzee do to not fall over whilst walking on two feet, and why is this the case? What helps humans to stand on two feet without falling over?
- It must bend its knees to avoid falling forward. Coz, C shaped vertebral column tends to put the centre of gravity in front of its feet.
- Humans: The secondary curvatures is in the bipedal vertebral column, compensate for the C curve and bring the centre of gravity back closer to the hips.
What do human females have to do to compensate for extra weight during pregnancy? How does this help them?
- Curvature and enforcement of lumbar vertebra.
- Dimorphous lumbar lordosis helps reduce shearing forces by foetal load.
Compare the position of foramen magnum in modern humans and quadruped.
Modern humans: Positioned anteriorly and oriented horizontally.
Vertebra is vertical.
Quadruped: Foramen magnum is dorsal.
Vertebra is parallel to ground.
What is pelvic inlet?
Pelvic inlet = circular space where head of baby enters, opening defined by inferior border of pubic symphysis, ischial tuberosities and coccyx.
In humans, the pelvic inlet grows larger in which direction? Anterior posteriorly or mediolaterally?
- Larger mediolaterally than anterior posteriorly.
Do efficient biped need a narrow pelvis? What must this balance with?
Efficient bipeds need narrow pelvis, but this must balance against need of birth canal wide enough for large brained baby.
Do humans and baby apes have small or big heads in comparison to the mother’s birth canal? Does this lead to short or quick deliveries, and thus does this lead to any complications in deliveries?
Baby apes have heads smaller than birth canal -> quick and easy deliveries.
Humans have longer heads than birth canals are wide -> 3-4 times longer deliveries than apes, run at higher complications.
Compare pelvis sizes and shape of moderns humans and chimpanzees.
Humans: basin shape, short, wide and curved ilium.
Chimpanzees: Long, flat and narrow ilium.
Are humans characterised by small or large acetabulum? And what is the function of this?
- Large
- To accommodate for large foetal head, that supports increase in body weight passing through hip during locomotion.
Are humans characterised by protruding or sunken anterior inferior iliac spine? And what is the function of this?
- Protruding.
- Good anchors for muscles used during walking.
In what direction does the ilium of bipedal hominid rotate?
Antero posteriorly.
What is the location of gluteus Medius and minimus muscle in relation to ilium and greater trochanter?
- Dorsal side of ilium.
- Distal to greater trochanter of femur.
The contraction of which muscle tilts the trunk toward limbs in contact with the ground, providing greater stability and balance.
Gluteal muscle.
Compare position of iliac ala in humans and apes.
Apes: parallel with back.
Humans: shifted laterally and flares more on sides.
Does the lateral orientation of ala abduct or adduct the hip joint?
Abduct.
