Unit 2 - Lecture - Bipedal Mechanics

Frankfurt Horizontal Head Allignment

Helps support balance

• Lower orbital margin to the top external auditory meatus

• Parallel to the ground

Gait

The manner of limb movements made during locomotion, specifically the pattern of how an organism moves on two legs

Foramen Magnum

The opening in the base of the skull that connects the spinal cord to the brain

Torque: Non-Humans

Listing of pelvis to non-support side

• Using a swing leg and a support leg to support body

Torque: Humans

Balancing

• Contraction of abductor muscles prevents listing on non-support side

For non-bipedal primates, what are the gluteal muscles used for?

Extenders

For bipedal primates, what are the gluteal muscles used for?

Abductors

What shows bipedal pelvic alterations?

Iliac faring

How does the curvature of the spinal column in bipeds help?

• Maintains hip joint in line with lower thorax in the lumbar vertebrae

  • Limits the front-to-back dimension of the pelvis in early hominins

How does the pelvis maintain bipedal ism for primates during childbirth?

Having a shorter, wider, and more basin-shaped pelvis with flared iliac blades to support upright posture and balance, and a birth canal that is mediolaterally broad

• Maintains transverse position during birth

Why does having a femur angled inwards help bipedalism in hominins?

This angle keeps the legs more directly under the body resulting in a more efficient center of gravity

What is the angle called where the degree of the femur is less than 90 degrees, resulting in a more efficient center of gravity?

Bicondylar Angle

How does the longitudional arch do for humans?

• Stores elastic energy and keeps structural rigor of the foot during the push off (toe-off) stage

• Acts as shock absorber, mitigating group reaction forces during mid-stance of gait cycle

Why and how did bipedalism emerge?

• Carrying weapons, tools, food, water, infants

• Long distance walking

• Moving between food trees

• Visual surveillance

• Feeding from buses

• Seed and nut gathering

• Male provisioning

What is body thermoregulation?

The maintenance of physiologic core body temperature by balancing heat generation with heat loss

• Bipedalism supports this as the upright posture allows for less solar radiation and more exposure to wind (cooling) leading to lower body temperatures/heat regulation

Exaptation

A trait which evolved in a specific environment, by chance then confers an adaptive benefit to a species in another newly occupied environment

Who, through measuring ancient tree covers and using fossil soils, reinforced the long-held idea that the foots of human origins are in the open grassland/savanna evironments of East Africa?

Thure Cerling