Humans as Bipedal Primates

Question 1

What does arboreal mean?

Answer 1

Acting/living in trees

Question 2

What is the Broca’s region?

Answer 2

A region of the brain concerned with the production of speech, located in the cortex of the dominant frontal lobe

Question 3

What is the brow ridge?

Answer 3

A bony ridge located above the eye sockets if all primates.

Question 4

What is the cranium?

Answer 4

The part of the skull that encloses the brain

Question 5

What is formen magnum?

Answer 5

The large opening at the base of the skull through which the spinal cord passes

Question 6

What is the nuchal crest?

Answer 6

A bony ridge at back of the skull. It is where the neck muscles and ligaments are attached in order to support the head.

Question 7

What is the mandible?

Answer 7

The lower jaw or jawbone

Question 8

What is an obligate biped?

Answer 8

Adapted for walking only on two legs, with no ability to walk on four.

Question 9

What is an opposable thumb?

Answer 9

A thumb that can be placed opposite the fingers of the same hand

Question 10

What is a prognathic jaw?

Answer 10

A “forward jaw”. Describes the degree to which the maxilla and mandible (the muzzle) extend forward of the face.

Question 11

What is a saggital crest?

Answer 11

A bony ridge on the top of the skull to which the jaw muscles are attached.

Question 12

What a valgus angle?

Answer 12

The angle the femur makes relative to the knee. Close to 90 degrees in non-human apes, less in bipedal humans.

Question 13

What is the wernicke’s area?

Answer 13

A region of the brain concerned with the comprehension of language, located in the cortex of the dominant temporal lobe.

Question 14

What is a zygomatic arch?

Answer 14

The bony arch at the outer border of the eye socket, formed by the joining of the cheekbone and the zygomatic process of the temporal lobe.

Question 15

What is bipedalism?

Answer 15

Having two feet and using two feet for locomotion.

Question 16

What is obligate bipedalism?

Answer 16

Walking only on two legs with a reduced ability to walk on all four.

The main trait that defines the hominin lineage and separates us from the rest of the apes.

Question 17

Why do humans have a barrel shaped ribcage?

Answer 17

Allows the arms to swing freely from side to side to assist with balance when walking upright.

Question 18

How have human feet evolved?

Answer 18

Toes are straighter and shorter. The big toe (hallux) is larger and more robust, aligned with the other toes for propulsion. Well developed arches. Robust heel that can absorb forces encountered during heel strike.

Question 19

What do chimpanzee feet look like?

Answer 19

Opposable hallux used for grasping branches. Foot lacks arches and the entire surface of the foot makes contact with flat ground.

Question 20

Human Foramen Magnum and Nuchal Crest

Answer 20

Foramen Magnum is nearer the centre of the skull and opens directly downward.

Humans have a cranium that rests on top of the vertebral column so the position of the Foramen magnum helps to balance the mass of the head above the spine.

Humans don’t have a large nuchal crest at the back of the cranium like the apeas.

Question 21

Ape Foramen Magnum

Answer 21

Foramen magnum lies towards the back of the skull.

Question 22

Human spine

Answer 22

S shaped spine brings the body’s centre of gravity directly over the middle of the pelvis and allows rhe spine to flex and absorb forces during locomotion.

Question 23

Chimpanzee spine

Answer 23

Bow shaped supports abdomen and helps to absorb forces generated by quadrupedal locomotion.

Question 24

Human pelvis

Answer 24

Shorter, broader, bowl shaped. Supports the gut when upright.

Question 25

Human femur

Answer 25

Valgus angle femur. Places feet directly below the centre of gravity as knee joints are closer to the mid-line than the hips.

Question 26

Environmental changes that led to selection pressure for Bipedalism

Answer 26

Relied on forest for food, shelter from the sun and hide from predators.

Forests broke up with climate change and the climate became cooler and dryer, giving way to scattered woodland and savannah.

Question 27

Advantages of Bipedalism (PEFT)

Answer 27

Predator avoidance: Stand up, look over tall grass, identify and avoid predators.

Energy efficiency: Biped walking uses less energy, longer journeys

Freeing the hands: Carry more food/weapons

Thermoregulation: Biped subject to less solar radiation while standing upright.

Question 28

Bipedalism and the hand: Humans

Answer 28

Shorter, straighter fingers, not required for brachiation.

Opposable thumb, more muscular and mobile.

Wrist mobility, fully rotate hands and extend hands.

Question 29

Human brain

Answer 29

Larger than chimpanzees, more complex brain, larger frontal lobe that allows us to have abstract and logical thought, imagination, complex language and artistic ability.

Cerebellum - refined fine motor skills and coordination, balancing, coordination

Larger frontal lobe - gives us the ability to have abstract and logical though, imagination, complex language and artistic ability

Question 30

Brachiating

Answer 30

Locomotion accomplished by swinging by the arms from on hold to another

Question 31

Habitual biped

Answer 31

Usually walks upright on two legs

Question 32

Prehensile

Answer 32

An animal’s limb or tail that is capable of grasping

Question 33

Sexually dimorphic

Answer 33

The differences in appearance between males and females of the same species

Question 34

Terrestrial

Answer 34

Of or related to the ground or earth, particularly describing animals that live on the ground

Question 35

Hominin

Answer 35

The group consisting of modern humans, extinct human species and all our immediate ancestors

Question 36

Human feet

Answer 36

• Opposable hallux (big toe) provides efficient toe-initiated push-off for propulsion
• Longitudinal arches in foot means humans can push off ground with toes
• Robust heel - forces of heel strike are absorbed by heel bone and balance while standing

Question 37

Human rib cage

Answer 37

Barrel shaped

Allows arms to be swung from side to side during bipedal locomotion

Question 38

Chimpanzee rib cage

Answer 38

Cone shaped.

Contains relatively large gut, allows for wide range of arm motion for brachiation

Question 39

How did the environment changing allow for bipedalism?

Answer 39

The mid-late miocene was a predominantly forested area. This meant that arboreal lifestyle to escape terrestrial predators, travel to food sources, nest and find shade was easy.

The climate became cooler, drier and water sources became limited. This resulted in grassland and open woodland.

This meant that bipeds had to range further to find food. They would have to carry objects and avoid predators. Being able to brachiate would become less important than being able to walk efficiently