W3 L1 human migration and skin colour

Question 1

Hypotheses of the origins of Homo sapiens

Answer 1

• believed to originated out of africa (but no non-African Homo sapiens fossils until 80,000ya)
  -multi regional origin from different population of homo erectus
  -out of africa, one population from africa and spread around the world, replacing older species

Question 2

Stringer origins of Homo: Recent African Origin (RAO) model

Answer 2

Recent African Origin (RAO) model
* modern humans first arose in Africa (approx 100 000 years ago)
* Indigenous premodern populations in other areas of the world were replaced
* little, if any, hybridisation between the groups

Question 3

Stringer origin: RAO and hybridisation model

Answer 3

allows for hybridisation between the migrating and indigenous pre-modern populations

Question 4

Stringer origin: assimilation model

Answer 4

• African origin for modern humans.
• no replacement, or population migration
• gene flow, changing selection pressures, and directional morphological change

Question 5

Multi-regionalism model

Answer 5

• denies recent African origin for modern humans.
• Modern humans arose in Africa, Europe and Asia
• genetic continuity over time and gene flow between populations

Question 6

Homo sapiens in Africa

Answer 6

-restricted in tropical central africa until 90kya
* Bone tools - (spears/ harpoons) and shell middens appear in caves in South Africa c. 70,000 years ago

Question 7

Human migration path

Answer 7

80kya start to spread out from central africa
60kya: diversification and second spread of africa lineage. Two new Arabia lineage from L3 africa
-40kya spread into South Asia aus and Eastern Europe
30-20kya: take over Europe and move to North America
After 20kya: spread into all of America
15kya colonization of Northern Europe, Asia , Canada post ice age
2k: pacific island, Madagascar and greenland

Question 8

Mungo Man

Answer 8

Found at Lake Mungo National Park,1974
* 40,000 years old (possibly older)
* About the earliest Homo sapiens remains found outside Africa and the Middle East

Question 9

Why did human took so long to leave africa and why did they spread so quickly

Answer 9

1/ climate
2/ critical population size
3/ sudden increase of intelligent

Question 10

climate reason in-depth

Answer 10

• 80,000 - 70,000 years ago = rapid environmental changes in Africa
• Mount Toba super-volcano (73,000 years ago) may have caused nuclear winter

Question 11

Critical pop indept

Answer 11

• Human population density too small to spread until 60,000 yr
• Higher population density drove expansion but no evidence for high population denstity

Question 12

Intelligent reason in-depth

Answer 12

• Sudden and distinctive appearance of advanced culture and technology about 50,000 years ago
• Indication of a neurological mutation, or strong environmental selection

Question 13

Evidence for intelligent increase (Klein hyphothesis

Answer 13

-appearance of art
* Evidence of ruins, and structures appearing after 50,000 years ago
* Evidence of ceremonies and rituals(elaborate burials)
* Evidence of ability to live in coldenvironment

Question 14

Problem with Klein hyphothesis

Answer 14

• Many aspects - art, structures, elaborate culture etc. around before 50,000 years
• No particular evidence for a “sudden” appearance
• Likely that a combination of factors

Question 15

cost of changing habitat and migration

Answer 15

• The first homo species - light skin, lots of hair (look at a chimp)
• About 1.6 mya - bipedalism meanthomo spp travelled long distances but this meant they could overheat
• Hairlessness (and increase in number of sweat glands) evolved as an adaptation to keep cool
• Our skin needed protection against the dangers of UV radiation

Question 16

Apocrine and sweat gland

Answer 16

Apocrine glands - open into the hair follicle, leading to the surface of the skin.
Eccrine sweat glands - over most of the body and open directly onto the skin’s surface. Assist in thermoregulation.

Question 17

The evolution of apocrine and eccrine sweat glands Advantage

Answer 17

• Forage in heat of day when the threat of predation is reduced
• Endurance running - running elicits higher sweat rates
  Might be Efficient way to cool our brain

Question 18

Eccrine and apocrine in primate

Answer 18

Species with high eccrine gland glycogen content associated with habitats exhibiting warm temperatures and low rainfall
* Species with increased capillarization were associated with high temperature

Question 19

Evolution of skin pigmentation

Answer 19

Melanin protects the skin from the harmful effects of UV radiation
But UV radiation needed to produce vitamin D

Question 20

Vitamin D hyphothesis

Answer 20

-melanocytes in skin need to protect us from UV damage but let enough UV through to have vitamin D synthesis
-different region have different melanin pigment depend on the area

Question 21

The problem with witamin D hyphothesis

Answer 21

Skin cancer is relatively rare in younger people
The selective pressure for darker skin to evolve would be greater if there was a reproductive benefit

Question 22

solution to vitamin D hyphothesis problem

Answer 22

Strong sunlight causes photolysis of folate
- protect spermatogenesis in male
-female: vital in offspring production, absecent cause neural tube defect