Fossil Evidence of Evolution from Ape-like Ancestors

Question 1

What did scientists learn by studying fossilised bones, in terms of evolution?

Answer 1

• the physical appearance for example of earlier hominins and how they changed over time
• bone size, shape and markings left by muscles show how hominins moved around and held tools

Question 2

What key features of fossils did palaeontologists look at to work out the evolutionary history of humans?

Answer 2

• bipedalism (spine and pelvic girdle)
• brain size
• teeth
• prognathism (projection of the jaw)
• palate shape
• cranial and brow ridges

Question 3

What was the most important adaptation that started humans on their evolutionary path?

Answer 3

• walking upright
• (habitual bipedalism)

Question 4

What did bipedalism enable early hominins to do?

Answer 4

• live in a greater variety of areas
• see danger from predators
• gather food and make and use tools with their completely free arms and more erect stance
• reduce the risk of over-heating as a large surface area is exposed for losing heat to the surroundings

Question 5

What are the disadvantages of bipedalism regarding the backbone?

Answer 5

• backbone no longer acts like a cantilever bridge between the hind and forelimbs
• subsequently put under a lot of stress

Question 6

What are the disadvantages of bipedalism regarding shock absorption?

Answer 6

• bipedalism removes the shock-absorber function of the shoulder blade that front-legged animals benefit from when they take a leap

Question 7

What are the disadvantages of bipedalism regarding the pelvis?

Answer 7

• the reshaping of the pelvis narrows the birth canal
• children are therefore born when they are smaller and relatively helpless

Question 8

What are the main indicators of a bipedal fossil?

Answer 8

• a foramen magnum that is positioned further forward
• a shorter, broader pelvis
• an S-shaped spine

Question 9

What does the larger brain that humans have evolved into make possible?

Answer 9

• better coordination of movement
• large amounts of information can be processed
• the development of speech and ultimately a written language for communication

Question 10

How do humans and apes differ in terms of prognathism?

Answer 10

Apes:
- a large and prognathous jaw
- (protruding jaw)
Humans:
- small jaw
- flat face

Question 11

How do humans and apes differ in terms of cranial and brow ridges?

Answer 11

• prominent in African apes
• smaller in humans

Question 12

How does the change in teeth and skull over time show a change in diet?

Answer 12

The following suggests that ape-like beings ate raw food, plant matter and meat, which required a great deal of processing:
- the teeth, especially the canines, were larger
- jaws were large and protruding
- cranial and brow ridges served as attachment for large chewing muscles

Question 13

What changes were evident regarding teeth and skull structures throughout human evolution and why?

Answer 13

• large teeth became unnecessary because early Homo species used tools to cut and grind food before eating
• later hominin species began to cook their food, meaning that it did not need the same amount of processing
• absence of cranial and brow ridges, which were not needed for muscle attachment, as the muscles for chewing were much smaller