Transcript Chapter 8 Primate and Hominin Origins Walking on two feet? • How does that work?

Chapter 8
Primate and Hominin Origins
Walking on two feet?
• How does that work?
Bipedalism!
• To walk habitually on two feet, there had to be
substantial changes to the pelvis, knees, and
feet.
• The Pelvis is comparatively much shorter and
broader than an Ape’s and extends around to
the side, stabilizing the line of weight
transmission from lower back to hip joint
• Example…
Human Os Coxae
• The human os coxae is
composed of three
bones (right side
shown).
Ossa Coxae (“hip bones”)
• (a) Homo sapiens.
• (b) Early hominin from
South Africa.
• (c) Great ape.
• Note the length and
breadth of the iliac
blade (boxed) and the
line of weight
transmission.
More Ossa Coxae
Bipedalism!
• To walk habitually on two feet, there had to be
substantial changes to the pelvis, legs/knees,
and feet.
• The Legs and Knees …
Longer legs, full knee extension
Land on heal
·
Push off toes
·
Longer limbs to
maximize movement
·
Full extension of Knee
Femur - The femur is angled inward, keeping legs under the body
Bipedalism!
• To walk habitually on two feet, there had to be
substantial changes to the pelvis, legs/knees,
and feet.
• The Feet…
Foot as stable suport
Models on WHY?
• Why we became bipedal (6 hypotheses)
Efficient bipedalism as the primary form of locomotion
is seen only in hominins.