Why bipedalism
Hominin evolution
Hominins.
•bipedal & non honing chewing. main features.
•secondary features. foraman magnum downward to bottom of skull. S shaped spine, ilium is short from front to back. legs loger than trunk & ARMS. HALLUX NOT OPPOSABLE BIG TOE. reconfigure gluteal muscles. angling of knees helps put feet below centre of gravity. arches on foot absorb shock. efficient walking.
•non honing. no diastema(canine fits between third premolar & lower canine - this hones the canine & keeps it sharp), small incisors. small blunt non projecting canines. thicker enamel.
Why hominins evolved
•Darling said bipedalism freed hands for weapons and reduced canine size. Increase intelligence and language. But tool use @3.3 mya & biped 6-8 mya. hunting also @ 2mya so not factor for evolution earlier.
•Rodman & McHenry patchy forest hypothesis. Grassland and forest with habitat lead to efficient locomotion like bipedalism.
•Lovejoy provisioning hypotheisis. Mother's depended on meals to give them food. So males gave food, thus holding food and bipedal walking. natural selection.
C neimitz. Amphibious lifestyle.
•Philip Reno. Little sexual dimorphism observed in hominin bones. Thus cooperative behaviour present as primatolo9gy shows.
Bipedalism benefits
•Ability to see greater distances. transporting food and children. Long distance running. Hands free to use tools and get skills.
•Negatively. Vulnerable to predators point more pressure on vertebral disc. Cause of injury. More pressure on heart to pump blood from the lens. It if one the person is disabled. But read of must have been very good.