Bipedalism Flashcards
What are advantages of bipedalism?
Improved cooling of the body’s surface
- less SA exposed to sun
- more SA exposed to breeze (cooking via convection)
Ability to see over grass
- see predators/prey
Hands free to carry tools/weapons/offspring/food
Energy-efficient locomotion
Favours long-distance, low-speedswaw
What is thought to have triggered the change to bipedalism?
Cooling of climate, causing loss of the near-continuous forests pre-hominins were thought to forage in
Woodlands became savannah, with sparse trees
Food resources became limited
Natural selection began to favour bipedalism
What are adaptations for bipedalism in the feet?
Elongated and robust calcaneous
Presence of both longitudinal and transverse arches (distribute weight, absorb shock)
Non-opposable big toe (for locomotion only)
What are the characteristics of ape feet?
Small calcaneous
Longitudinal arch only (flat-footed)
Opposable big toe, for locomotion + grasping
What are adaptations for bipedalism in the pelvis?
Pelvis is bowl-shaped
(supports abdominal organs, large SA for muscle attachment)
Short top -> bottom
(^ stability when upright)
What are the characteristics of ape pelvises?
Flattened and narrow
Tall top->bottom
What are adaptations for bipedalism in the hip and knee?
Deep acetabulum
(accommodates large femoral head + carrying angle)
Carrying angle
(transmits weight under centre of body, ^ balance)
Arms shorter than legs
(lowers centre of gravity)
Longer femur
(^ stride length, more effective travel)
Weight transmission through outer condyle of knee joint
What are characteristics of ape hips and knees?
Shallow acetabulum
No significant carrying angle
Arms longer than legs
Shorter femur
Weight transmission through inner condyle of knee joint
What are adaptations for bipedalism in the spine?
S-shaped curve
(shock absorption, transmits weight thru centre of body)
Wedge-shaped, large, thick lumbar vertebrae
(^ SA for muscle attachment)
What are characteristics of ape spines?
C-shaped curve
Lighter lumbar vertebrae
Larger upper vertebrae
(^ SA for neck muscle attachment)
