← Trends in human evolution
4 Bipedalism: the skeletal evidence
| Feature | In humans (bipedal) | Why |
|---|---|---|
| Foramen magnum | Central, underneath the skull | Skull balanced on top of a vertical spine |
| Spine | S-shaped (double curve) | Centres weight over the pelvis; absorbs shock |
| Pelvis | Short, broad, bowl-shaped | Supports organs; anchors walking muscles |
| Femur | Angled inward (valgus / carrying angle) | Brings knees & feet under the body’s midline for balance |
| Legs | Long relative to arms | Efficient striding gait |
| Foot | Arched, non-opposable big toe (in line) | Rigid lever for push-off; arches absorb shock |
Advantages of bipedalism
- Frees the hands → carry food/young, use and make tools.
- See over long grass → spot predators and prey.
- Energy-efficient over long distances.
- Less body surface exposed to midday sun → better thermoregulation.