Lecture 8- Human migrations and "race"

Question 1

What are the Omo sculls?

Answer 1

• Omo 1 and 2 -Found 1967-1974 Omo River, -Ethiopia 195,000 years old -Earliest Homo sapiens

Question 2

What are the hypotheses as to the origin of Homo sapiens?

Answer 2

• Origin outside Africa (e.g. European Homo heidelbergensis or Asian Homo erectus) – There were no non-African Homo sapiens fossils until 80,000 ya • Multi-regional - Homo sapiens descended from different populations of Homo erectus • ‘Out-of-Africa’ - Homo sapiens originated from one population in Africa and spread around world, replacing older species

Question 3

What is the Recent African Origin (RAO) model of Homo sapiens origin? (i)

Answer 3

• 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 4

What is the RAO and hybridisation model of Homo sapiens origin? (ii)

Answer 4

• allows for hybridisation between the migrating and indigenous premodern populations

-second idea, less conservative, allows for hybridisation (some interbreeding)

Question 5

What is the assimilation model of Homo sapiens origin? (iii)

Answer 5

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

Question 6

What is the multi-regionalism model of Homo sapiens origin? (iv)

Answer 6

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

Question 7

What did mitochondrial DNA reveal about the Homo sapiens origin?

Answer 7

• Analysed mitochondrial DNA sequences from 147 individuals
• Found that all modern non-African humans descend from a single African lineage

-evidence for origin of homo sapiens = mitochondrial DNA (maternally derived, highly conserved)

Question 8

What are the ideas of mitochondrial Adam and Eve?

Answer 8

• All modern humans descended from a single female who lived 200,000 years ago (‘Mitochondrial Eve’) • Original analysis of Y-chromosome (male- inherited) indicates a single male ancestor (‘Y-chromosome Adam) - 70,000 years after Mitochondrial Eve! • A recent study of an African American found that his y-chromosomal DNA dated to approx 330,000 – 130,000 years after Mitochondrial Eve (Mendez et al 2013). –indicates a single male ancestors (dated 70 000 years after the female) -what is happening?= probably that the Y chromosome mutates less, but difference in reproductive success in males, -one african american= dated to 330 000 years old DNA -maybe lends credence to the idea of mixing, probably not just one male and female ancestor!

Question 9

Up to when where Homo sapiens constrained to tropical central Africa?

Answer 9

• Homo sapiens - restricted to tropical central Africa until c. 90,000 years ago.

Question 10

When did the first evidence of Homo sapiens in S. Africa appear?

Answer 10

• Bone tools - (spears/ harpoons) and shell middens appear in caves in South Africa c. 70,000 years ago

Question 11

From when is the first evidence of humans in Israel?

Answer 11

• Burials of human skeletons found in Israel (Qafzeh caves) - 90,000 years old - suggest ritual burial

Question 12

What was the temporary setback in the expansion of Human sapiens population?

Answer 12

-disappear from the fossil record for about 10 000 years in the middle east -probably due to the ice age at the time

Question 13

What was the Homo sapiens movement 80 000 years ago like?

Answer 13

-

Question 14

What was the Homo sapiens movement 60 000 years ago like?

Answer 14

-• Diversification and second spread of African lineages

• Appearance of two new lineages in Arabia (derived from L3 African lineage)

• probably only a couple of hundred individuals
• now a second wave of african lineages, letters= lineages

Question 15

What was the Homo sapiens movement 60 000-40 000 years ago like?

Answer 15

• It was all go!
• Rapid spread of Humans across South Asia and into Australia
• Also spread to north to Siberia and Eastern Europe

Question 16

What is the Mungo man?

Answer 16

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

Question 17

What are some of the questions regarding the Homo sapiens movement out of Africa?

Answer 17

1. What took them so long? 2. Or, why didn’t they leave sooner? 3. What made them leave when they did 4. And, why did they then spread so quickly?

Question 18

How could climate explain the length of time it took Homo sapiens to leave Africa?

Answer 18

• 80,000 - 70,000 years ago = rapid environmental changes in Africa • Mount Toba super-volcano (73,000 years ago) may have caused nuclear winter -maybe cut off and couldn’t moev anywhere (geographical reasons) -nuclear winter?= would have been very cold, wouldn’t want to move beyond where it is warm (evidence in Sumatra= lake)

Question 19

How could critical population size explain the length of time it took Homo sapiens to leave Africa?

Answer 19

• Human population density too small to spread until 60,000 yr • Higher population density drove expansion -Problem: no evidence for high population density -reached a critical population density= drove expansion -do not have any good evidence for this, almost to the contrary -shells: the expectation would be if huge population size= the shells would get smaller as the big ones would be eaten (but the shells actually get bigger, larger than average)

Question 20

How could a sudden increase in intelligence explain the length of time it took Homo sapiens to leave Africa?

Answer 20

• Sudden and distinctive appearance of advanced culture and technology about 50,000 years ago • Indication of a neurological mutation, or strong environmental selection -evidence: appearance of advanced culture (50-60 000 yrs ago) -The 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 cold environments (Klein’s hypothesis)

Question 21

What are the problems with Klein’s hypothesis?

Answer 21

• Many aspects - art, structures, elaborate culture etc. around before 50,000 years • No particular evidence for a “sudden” appearance -the problem is that it is not just after 60 000 years ago, the culture, we saw burial in Israel, 90 000 years ago -we are not seeing evidence to sudden appearance of intelligence, probably more gradual developing of intelligence rather than sudden mutation in the DNA

Question 22

What was the Homo sapiens movement 30 000-20 000 years ago like?

Answer 22

-takeover of Europe and first moves in North America

Question 23

What was the Homo sapiens movement 20 000-15 000 years ago like?

Answer 23

-spread throughout the rest of the Americas

Question 24

What was the Homo sapiens movement 15 000-2000 years ago like?

Answer 24

-Colonisation of Northern Europe, Asia and Alaska/Canada post Ice-Age

Question 25

What was the Homo sapiens movement 2000 years ago until the present like?

Answer 25

-Spread to Pacific Islands, Madagascar, Greenland

Question 26

What is the concept of race and its associated problems?

Answer 26

-“Race is a thoroughly contentious topic…. few other concepts used in the conduct of ordinary science are the subject of such passionate debate about whether they actually exist” -have opposing views on the existence of race: -Human ‘races’ are not distinct lineages [and] are not, and never were, ‘pure’. -A great deal of variation within groups is compatible with biological race concepts. It is time for geneticists and anthropologists to stop worrying about what does not exist and to discover what does exist.

Question 27

How much of the genetic diversity of humans is accounted for by race?

Answer 27

15%

Question 28

What are some differences in people of different races?

Answer 28

• There are still genetic differences: – Pacific Islanders have higher levels of diabetes – Africans/Mediterreans (origin) have higher levels of sickle-cell anaemia – Europeans can break down lactose • But difficult to define races based on these genetic differences ‘Race’ is often equated to skin colour -sickle cell anaemia= great advantage in malaric regions -europeans can break down lactose, except in finland not as much -can we put it down to race?

Question 29

What was the evolution and maintenance of skin colour like?

Answer 29

• The first homo species - light skin, lots of hair • About 1.6 mya - bipedalism meant homo spp travelled long distances and could overheat • Hairlessness (and increase in number of sweat glands) evolved as an adaptation to keep cool -PROBLEM…: Our skin needed protection against the dangers of UV radiation -our first ancestors= very pale -become endurance athletes, move a lot, we overheat is a problem -evolution of hairlessness= to allow heat to escape and avolution of sweat glands= allows us to move big distances without overheating

Question 30

How did the evolution of skin pigmentation happen?

Answer 30

-Melanin protects the skin from the harmful effects of UV radiation -But…we need UV radiation to produce Vitamin D -with losing hair= exposure to UV radiation -melanocytes produce a pigment melanin, it sits on the top of our skin and protects our skin from UV radiation

Question 31

What is the original Vitamin D hypothesis?

Answer 31

• need a balance of how much you block so you still get enough vitamin D
• how dark you can be to avoid skin cancer and how much you need vitamin D

Question 32

What is the problem with the original Vitamin D hypothesis?

Answer 32

-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 -the sole reason for evolution of skin colour? -problem is: skin cancer is rare in young people, need 20 years of skin damage before you see skin cancer= problem then that it is not going to be a selective pressure as much as if it were pre-reproduction -vit D degrades vit B- folate, important for reproduction! if sun going through= folate is broken down,

Question 33

What is the solution to the problem with the original Vitamin D hypothesis?

Answer 33

Strong sunlight causes photolysis of folate The reproductive link… Males - spermatogenesis Females - vital in offspring production - absence causes neural tube defects -so this is the selective pressure

Question 34

What is the revised Vitamin D hypothesis?

Answer 34

-mix of these factors

Question 35

What was revealed by comparing the levels of UV radiation and the skin colour of the indigenous human population?

Answer 35

-high geographical correlation of high UV and dark skin

Question 36

PIC12What is the situation like in an extreme UV radiation environment for a light skinned and dark skinned human?

Answer 36

-

Question 37

What is the situation like in a low UV radiation environment for a light skinned and dark skinned human?

Answer 37

-

Question 38

What are the questions from this lecture?

Answer 38

• What is the evidence for a single origin of modern man in Africa? • What factors may have led to the spread of humans around the planet starting approximately 50,000 years ago? • Whatisrace?Whatistheevidenceforand against the concept as applied to humans? • Why did skin colour evolve, and why are many humans now mismatched to their environment?