Bipedalism- Lower body changes

Question 1

What is the Ape Pelvis

Answer 1

It is long and narrow with the femoral attachment straight down.

Question 2

Human pelvis

Answer 2

Bowl shaped pelvis. Short and broad. muscles involved support the body during the upright posture and locomotion is more effective.

Internal organs and spine are positioned over the leg bones and thus centre of gravity = more energy efficient

Question 3

Selection pressures of ape to hominin -lower body?

Answer 3

The pelvis needed to produce more efficient bipedal locomotion. Brain and skull of offpsring needed to be able to pass through the birth canal.

Question 4

Why did h.sapiens birth canal change

Answer 4

to support bipedal locomotion, more energy efficient

Question 5

why was it easier to walk on 4 legs instead of 2 for apes?

Answer 5

apes required a large amount of muscles to keep an upright position

Question 6

Why did bipeds have a valgus angle?

Answer 6

valgus angle is larger than apes as femur is angled inwards rather than straight down. Centre of gravity in bipeds towards the midline of the body, with the knees directly underneath the body instead of the side

Question 7

why did bipeds have long leg bones?

Answer 7

Arms were no longer needed for a arboreal lifestle, they no longer used for brachiation. More time was spent on the ground rather than branching on trees, = more advantageous to have longer legs = longer stride

Question 8

Foot changes for bipeds?

Answer 8

Bipeds= toe elongated and straight in line with other toes, arched foot that acts as a shcok absorber and spring = long distance. heel bone is enlarged accomodates “heel toe” locomotion

Question 9

ape foot

Answer 9

diverging large toe that aids climbing and an arboreal lifestyle. Flat footed

Question 10

why do bipeds have a straight stride when walking?

Answer 10

the positions of the gluteus Maximus muscle attachment is behind the pelvis= straight stride.