Ch. 19 Human Ancestors

Question 1

What did the early hominins body and movement resemble, and how was this advantageous for future evolution

Answer 1

• ape-like arms and hands (suitable for tree living)
• moved over small branches in bipedal manner
  > this locomotion used for walking over large gaps of canopy

Question 2

What was the environmental change that allowed the evolution of bipedalism

Answer 2

• 5-6 million years ago= temp fall= forest areas diminish in size // open areas

Question 3

As the environment changed for early hominins, what did natural selection favoured

Answer 3

natural selection favored apes that were better at bipedal walking

Question 4

What are 5 advantages of an erect stance

Answer 4

>

Increased range in vision for detecting prey and predators at a greater distance
Increased size, deterring predators
Hands free for carrying food, and perhaps tool use
Higher reach when picking fruit from trees
Improved cooling of the body 

( C, V, C R, S)

Question 5

How does bipedalism favour the cooling of the body

Answer 5

1. When vertical (not horizontal or quadrupedalism) sun strikes smaller fraction= avoid overheating
2. upper body above ground where there is more wind to help cool the body and where air temperatures may be marginally lower than at ground level

Question 6

What are the two variations for australopithecine

Answer 6

Gracile

Robust

Question 7

What are two examples of gracile australoopithecines

Answer 7

a.africanus, a.afarensis

Question 8

What are the differences between robust and gracile

Answer 8

Robust

• large molar teeth + sharp canine
• large jaw + chewing muscles
• Skull= large saggital crest

Question 9

What is the cranial capacity for australopithecine

Answer 9

400-500

Question 10

What is the cranial capacity for homo habilis

Answer 10

590-775

Question 11

What is the cranial capacity for homo erectus

Answer 11

1075

Question 12

What is the cranial capacity for neanderthal

Answer 12

1469

Question 13

What is the cranial capacity for homo sapiens

Answer 13

1350

Question 14

What were 5 general trends in evolution of the skull

Answer 14

• cranial capacity
• brow ridge
• forehead
• prognathism
• dentation

Question 15

what is an example of a robust australopithecine

Answer 15

parathropus robustus

Question 16

What was the trend in cranial capacity and why did it occur

Answer 16

• more convolutions
• more complex (// larger)
• cerebral cortex larger
• enabled as meat= high energy

Question 17

what was the trend in brow ridge and why did it occur

Answer 17

• reduced/absent brow ridge

- because larger brain> larger skull > brow vertical and lack ridges

Question 18

what was the trend in forehead and why did it occur

Answer 18

• flatter face + noticeable forehead
• because 1. frontal lobe expanded
  2. skull larger > more skull dedicated cranial portion

Question 19

what was the trend in prognathism and why did it occur

Answer 19

• less prognathic
• because
  1. balance/ bipedalism
  2. reduction of size of teeth

Question 20

what was the trend (3) in dentition and why did it occur

Answer 20

1. decrease in size and proportional teeth because less herbivorous diet
2. u shape to parabolic
3. diastema reduce as canines reduced

Question 21

At what point did the chin begin to form

Answer 21

homo habilis

Question 22

Why eww neanderthals cranium so large

Answer 22

required for control of extra muscles

Question 23

what was significant about the overall shape of the neanderthal skull (back)

Answer 23

• bun shaped