Biology Now, 2e

310 ■ CHAPTER 17 Animals and Human Evolution

BIODIVERSITY

Pelvis

The face is

relatively

flat.

The spinal cord

enters from the

center of the skull.

The face is

pulled forward.

The spinal cord

enters from the

rear of the skull.

The pelvis—frontal view

The skull and its relation

to the spinal cord

Shifting weight

support

The hip bones in humans

allow an upright posture.

Humans have an

upright posture.

Other apes have a posture

supported by four limbs.

Overall skeletal

structure

Structure of foot

and function of big toe

The angle of weight

support in other apes...

The arch and heel

are pronounced.

...differs from that

in humans.

The big toe is

not opposable.

The big toe is

opposable.

Other apes Humans

There is no arch.

Figure 17.8

Evolutionary differences between humans and other apes

The switch to walking upright required a drastic reorganization of primate anatomy, especially of the hip bones. M