13 + 14. Human Evolution

Question 1

Where did the mammals evolve from?

Answer 1

• Mammals evolved from a separate group of reptiles

- Became dominant after meteor wiped out all animals

Question 2

What are some distinguishing structural features of mammals?

Answer 2

• Fusion, reduction of bones
• Single jaw bone, and bones to amplify sound in the ear
• Opposing, specialised teeth (molars, canines)
• Solid strong pelvic girdle

Question 3

What are some physiological distinguishing features of mammals?

Answer 3

• Endothermic with hair/fur insulation, sweat glands
• 4 chambered heart
• Mammary glands
• Most mammals have a placenta to feed the young in the mother

Question 4

What are the two subclasses of mammals?

Answer 4

• Subclass Theria= mammals

- Subclass Eutheria= young fed by placenta to an advanced stage

Question 5

What is the order that humans belong to?

Answer 5

Primates

Question 6

How did the environment change after the meteor?

Answer 6

Before the meteor - a warm earth period
After the meteor - a 30 million year hot earth period

More rain, more forests - trees everywhere! The forest was widespread and continuous

Question 7

Who are the 2 primate ancestors?

Answer 7

Plesiadapids and Adapids

Question 8

What are some characteristics of the plesiadapids?

Answer 8

• Coexisted with dinosaurs
• Lived in trees during the warm earth era
• Squirrel like with claws, big incisors and small brains

Question 9

What are some characteristics of the adapids?

Answer 9

• First true primates
• Tree living during the hot earth period
• Nails instead of claws
• Opposable toes and thumbs
• Forward facing eyes with bigger Brian’s

Question 10

What are some characteristics of wet nosed primates (prosimians)?

Answer 10

Lemurs

• least specialised primates with hands and binocular vision
• Long noses for heightened smell
• Wet nose with a split lip
• Much of the brain is the nasal area

Question 11

In order to be able to leap in tree, what features do you need?

Answer 11

• Need binocular vision to judge distance
• Forward facing eyes protected by a ring of bone
• Large brain for decision including visual processing and the control of locomotion

Question 12

What features in the hands are needed for leaping in trees?

Answer 12

• Grasping digits (not paws)
• Opposable thumb and 1st toe
• Can use upright posture

Question 13

How is the primates order further split up?

Answer 13

• Split into eight groups, almost all in tropical forests
• Wet nosed are the least specialised
• Dry nosed include tarsiers, new and old world monkeys, gibbons, great apes and humans

Question 14

What changes in the sense structures were observed for simians?

Answer 14

• Dry nose with no split lip giving reduced smell ability
• But more complex sounds could be heard
• No reflective eye layer

Question 15

What is the parenting like for most mammals?

Answer 15

• Birth triggers the hormone oxytocin which triggers mother to bond to infants smell and starts lactation
• Vasopressin bonds males to the smell of a female

Question 16

What is the parenting change seen in simians?

Answer 16

• Reduced smell
• Parental care lasts beyond lactation
• Young females learn complex parenting skills, so the brain rather than hormones control parenting
• Tactile relations release the reward hormone B endorphin which reinforces bonding

Question 17

How have hominoids adapted for brachiating?

Answer 17

• Mostly larger than monkeys with larger brains
• No tails, but adapted for brachiation through longer arms and shorter legs
• Flat chests, shoulder blades at the back
• rotating arms

Question 18

What genus is enclosed in the pongids family?

Answer 18

The orang-utan, chimps and gorillas

Question 19

What are the 6 skeletal differences due to erect posture?

Answer 19

1. The neck is under the skull rather than behind for balancing the head on spine
2. S shaped spine rather than arch
3. Pelvis is bowl shaped, wide rather than long
4. Heel bones support weight
5. Foot arched rather than flat for shock absorption

Question 20

What is the function of having a bowl shaped pelvis?

Answer 20

Supports the abdomen, muscles and femur for balance

Question 21

What are the skeletal differences due to erect posture in the lower body region?

Answer 21

• Femur is angled inwards
• Knee joint locks straight from the side
• Big toe points forwards

Question 22

How have the jaw muscles of humans evolved?

Answer 22

• We have weaker jaw and smaller muscles
• The gene MYH16 for muscle protein mutated
• Allows for a larger thinner skull

Question 23

How has the brain growth and energy evolved for humans?

Answer 23

• Genes mutated giving more neutron branches in developing brain
• 3 gene changes gave rise to wider arteries, more glucose shunted from the blood to the brain - more energy to the brain

Question 24

What are the differences in the teeth for humans?

Answer 24

Dietary differences are shown in 1) the rounded, rather than rectangular shape of the palate

2) Th size of the canines have reduced and there is no diastema
3) Molars are more worn

Question 25

How did the first walking apes have an advantage?

Answer 25

- As africa began to cool and dry, apes that could move faster between trees would have an advantage - they were good climbers due to long arms and fingers, long toes and prehensile big toe, skull like normal ape

Question 26

What structural features were present in Lucy, australopithecus afarensis?

Answer 26

- More erect with a forwards big toe and female angled inwards - Long arms, curled fingers, legs only just longer than arms suggests they still climber trees as well

Question 27

What features were seen in the australopithecus jaw?

Answer 27

- Canine size is intermediate - Diastema small but present - Palate arch partly rounded

Question 28

What was the skull of the australopithecus like?

Answer 28

- Low forehead with prominent brow ridges - Projecting face - Ape range cranial capacity

Question 29

What homo species preceded sapiens?

Answer 29

- Homo habilis and h. rudolfensis at the same time - They had a larger brain region for speech and communication - Homo erectus had a large cranial size, brow ridges still present - stone tools

Question 30

Why was Homo erectus so successful?

Answer 30

- Less sexual dimorphism giving rise to possible pair bonding - Less hair on body so they wore fur, enabling them to live further north in Eurasia - Acheulean tools and organisation of hunting protects agains predators

Question 31

Was there gene mixing with the neanderthals?

Answer 31

- No gene mixing with modern humans in the Mt DNA | - Nuclear dna observes mixing

Question 32

What are the distinct skull features of H. Sapiens compared to other hominoids?

Answer 32

- Highly domed skull with a flat face - Small brow ridges - Rounded back of skull - Jutting chin allows space for tongue movement and language