Human Evolution

Question 1

Sagittal crest

Answer 1

Ridge at the top of the skull to which the jaw muscles are attached. The sagittal crest is more prominent in primates because of their high fiber diet.

Question 2

Foramen magnum

Answer 2

The hole at the back of the skull through which the spinal cord enters the skull. The foramen magnum is more central in humans than it is apes. This is because apes are quadrupedal and humans are bipedal.

Question 3

Nuchal crest

Answer 3

The part of the skull where the neck muscles attach. The nuchal crest is larger in apes than it is in humans because apes are mostly quadrupeds and have to keep their head from drooping.

Question 4

Brow ridge

Answer 4

Heavy bone over the eyes. This is to protect the eyes. The powerful chewing action of ape jaws sets up stresses in the skull and in the lower jaw. These are resisted by brow ridges above the eye sockets, and also by a simian shelf which strengthens the inside of the lower jaw. Humans have no brow ridge.

Question 5

Cerebral cortex

Answer 5

Apes have a much smaller brain size of 450cm^3 vs 1400cm^3, and no specialised area for language. Humans cerebral cortex is well developed therefore they have better and higher level of thinking, speech, memory etc.

Question 6

Jaw

Answer 6

The tooth row (dental arcade) is parabolic (bow-shaped) in humans but is “U” shaped in apes.

Question 7

Canines

Answer 7

Human canines are about equal in size in the two sexes, while those in great apes are considerably larger in males than in females. The large canine are used predominantly for threat displays.

Question 8

Spine/pelvis

Answer 8

Apes spines are “C” shaped with a longer narrow pelvis while humans spines are “S” shaped with a shorter straight stiff broader more bowl-like pelvis

Question 9

Hairs

Answer 9

Apes hair is longer and more coarse with few sweat glands while humans have the same number of hair but it is much finer with more sweat glands

Question 10

Knees

Answer 10

Apes knees bend outwards under the hips as their femur is angled into the knee so when they lift one foot off the ground, they lose balance. They must lean to one side to counterbalance causing a swaying motion.
Humans knees are angled inwards (valgus angle) so the knee sits nearer to the centre of gravity. Knee joint is larger. More efficient walking as the organism does not wasate energy swinging from side to side and is much more balanced as they walk.

Question 11

Big toe

Answer 11

Apes feet have opposable big toe so the foot is able to grab things. Their feet are also flat.
Humans have a forward facing big toe and foot is arched which acts as a shock absorber and enables humans to spring off their feet when walking therefore making walking more efficient.

Question 12

Fingers

Answer 12

Apes fingers are more curved and less mobile. Like all primates both can grip objects with a power grip but humans also have precision grip.

Question 13

Three advantages of being the “Naked Ape”

Answer 13

1) Hair on the head is used to reduce heat loss and to reflect heat off the head therefore helping keep the brain at the correct temperature
2) Having reduced body hair means the control of parasites became easier which was important when hominins started living in home bases
3) By having shorter hair and well developed sweat glands all over our body, we increased heat loss which helped keep us cool

Question 14

BIPEDALISM QUOTE TO REMEMBER

Answer 14

All primates show a tendency to an upright posture at times - such as when feeding a baby, swinging from trees, or just sitting. Humans have taken this to the extreme and walk on two legs all of the time. Hominins were bipedal by nearly 4MYA. It is thought that being bipedal allowed humans to exploit the ground niches, which probably offered more variety of food at a time when forests were shrinking. It certainly allowed humans to use their hands in ways that no other primate can. This change to bipedalism was probably the most important step in our evolution because it freed the hands, allowing us to take advantage of our larger brain.

Question 15

Bipedalism Advantage 1: Carrying Young

Answer 15

Human females do not have enough hair to grasp, nor do their babies have prehensile feet to hang on, so females must carry their young. This requires free arms. A hominin that had a less opposable big toe would have been less good at clinging onto its mother, so its mother would have had to rely on its legs to walk so she could carry he rbaby. This would select any feature that made her better at bipedalism, such as a less opposable big toe. This, in turn, would make the young less able to grasp its mother and more dependent on being carried.

Question 16

Bipedalism Advantage 2: Free hands

Answer 16

Free to carry objects such as food, tools etc. More food could be carried back home for sharing

Question 17

Bipedalism Advantage 3: Heat regulation

Answer 17

Bipedalism raises the body surface higher above the ground, where there is more wind and cooler temperatures. Greater wind flow means more heat loss by convection. Bipedalism also conserves body water by needing less evaporation to cool down. Standing upright also reduces direct solar exposure during the time of day when the solar radiation is most intense. The brain is especially sensitive to increased temperature, so we have kept hair on the head to reduce the heating effect of the sun.

Question 18

Bipedalism Advantage 4: Standing upright

Answer 18

Allows animals to see predators more easily.

Question 19

Bipedalism Advantage 5: Energy

Answer 19

By being bipedal less energy is needed to move long distances as the bipedal motion is more efficient.

Question 20

Bipedalism Disadvantage 1: Birth

Answer 20

Giving birth to a larger headed baby means babies are born helpless and birth is painful. Because they are born so helpless they require a lot of parental care. Takes about a year before a baby can walk.

Question 21

Bipedalism Disadvantage 2: Spine

Answer 21

Humans are prone to back ache due to the “S” shaped spine

Question 22

mtDNA

Answer 22

Mitochondrial DNA. Passed down the female line unchanged except by mutation.

Question 23

Y chromosome DNA

Answer 23

Passed down the male line unchanged.

Question 24

Oldowan

Answer 24

• first used by homo habilis
• very simple tools with a few flakes remvoed
• used to chop and scrap

Question 25

Archeulean

Answer 25

- first used by homo erection and archaic homo sapiens - bi-faced, teardrop shaped which had been carefully crafted to a standard design - much more crafted than oldowan as more chips removed - tools took much longer to craft with an average 65 blows per tool - used as hand-axes and cleavers - made for specific jobs e.g. basic design altered to make scrapers

Question 26

Mousterian

Answer 26

- first used by neanderthals - sophisticated tools which were finely worked, made of stone but often had other materials attached for more accurate handling - require high levels of skills and time to learn and make e.g. spear, axes, scarpers

Question 27

Upper Paleolithic

Answer 27

- first used by homo sapiens and neanderthals - tool making techniques were further refined - most flake edges were sharpened for cutting - had a large variety of tools for many different jobs - shaped to fit into handles - not just made of stone, materials including bone, antlers, guts, plant fibres etc. - tools were things like needles, ropes, nets, snares etc. - allowed hunters to kill much larger prey and process it quickly, as well as allowed them to preserve the food. - animal hides would be stretched over wood to make tent type structures, they also made clothes out of the hides

Question 28

Farming & domestication of animals

Answer 28

- early humans were nomadic hunter-gatherers relying on what was present in the environment and moving as the population grew or resources ran out. later they followed the herds around and eventually became less nomadic.

Question 29

7 Farming & domestication of animals advantages

Answer 29

1) food supply easier to obtain with a much more dependable food source 2) fewer people died of starvation 3) fewer people needed to work at providing food for many 4) specialised skills able to be developed by those not involved in getting food and while living in a permanent settlement meaning they get better at their job benefiting the whole group 5) as people became more skilled at farming they developed more permanent settlements at the best sites near sources of water. They were able to produce more food than they needed so traded with other people for other things they needed. 6) more time to develop skills such as art, poetry etc. 7) made technological advances (wheel, plough, hoe) which eventually led to the Industrial Revolution

Question 30

5 farming & domestication of animals disadvantages

Answer 30

1) their diet was restricted to what they could grow 2) became more dependent on the weather for their crop growth 3) because there was a higher population, disease carrying and disease causing organisms flourished as they had more people closer together to infect e.g. rats, fleas, viruses etc. 4) growing crops etc. is very time consuming 5) people begin to fight over ownership of animals and territory

Question 31

Multiregional theory

Answer 31

Some homo erectus left Africa about 1.8MYA and spread to Europe and Asia. In the three areas, homo erectus evolved parallel into homo sapiens, with some genetic contact and gene flow between populations in the different areas.

Question 32

Evidence to support the Multiregional theory

Answer 32

- Some transitional fossils have been found in many places especially the Asian fossils which show a clear transition from older hominid to modern homo sapiens. - High levels of gene flow would be needed for this hypothesis to be correct which is not very likely

Question 33

Why is multiregional theory questioned

Answer 33

This hypothesis is highly questioned based on the more recent genetic research especially the use of mtDNA and Y chromosome DNA. For this hypothesis to be correct current humans would have large genetic variation. However, when mtDNA and Y chromosome DNA is analysed, there was less variation than expected. This means they didn;t leave Africa until much later.

Question 34

Out of Africa Theory

Answer 34

We left Africa as homo sapiens about 200,000YA. So we evolved from homo erectus in Africa. They spread gradually replacing and making other hominin species extinct as they came upon them.

Question 35

is OoA first or second movement

Answer 35

This was the second movement OoA as some homo erectus left Africa about 1.8MYA but they became extinct outside of Africa due to the harsh environment at the time. Those that remained in Africa evolved into homo sapiens and left much later.

Question 36

Evidence to support the Out of Africa theory

Answer 36

- Every person who is not of African descent is related to a single group of about 200 people who left Africa and crossed the Red sea - All modern humans have similar genes and nuclear sequences. If parallel evolution had occurred there would be much greater variation in human genetic makeup. - When mtDNA and Y chromosome DNA was analysed it was observed that the DNA hasn't changed much. Therefore it has been predicted that "Mitochondrial Eve" left Africa much later, about 100,000YA. - People who live in Africa have the greatest genetic variation as they have been around for the longest time and have had more time to develop genetic diversity. The greatest variability is found within African populations which are the oldest. There is less genetic diversity in Asian and European populations which suggests they are not as old as African populations.

Question 37

Out of Africa with some genetic variation theory

Answer 37

Mix of both OoA and multirgegional because it suggests that homo erectus evolved into homo sapiens in Africa and then migrated to other areas. Majority of human ancestry comes from a single African origin because of interbreeding with other hominin species like neanderthals and denisovans.

Question 38

Evidence to support Out of Africa with some genetic variation theory

Answer 38

Moderns humans share common ancestry with a single African origin, with traces of interbreeding with archaic humans like neanderthals and denisovans. MtDNA studies indicate all modern humans must share a common maternal ancestor, and y chromosome DNA studies indicate all men share a common paternal ancestor. (both ancestors are from Africa around 200,000YA) Archaeological findings like tools and artifacts show progression of human culture that began in Africa and spread to other parts of the world.