Lecture 14 - Out of Africa 2

Question 1

what are 2 key questions asked when studying the origin of modern humans?

Answer 1

1) How many waves of migrations were there?

2) was there two-way gene flow between Africa and Eurasia?

Question 2

Where does Homo heidelbergensis fit in?

Answer 2

• Appears to have evolved from H. erectus in Africa or Europe at least 600,000 years ago, spread out to colonize both Africa and Europe, and in the process gave rise to H. neanderthalensis (in Europe/Western Asia by 400,000) and H. sapiens (in Africa by 200,000)

Question 3

why do we have good knowledge of the Neanderthals?

Answer 3

they lived mainly in caves so were well preserved

Question 4

describe the neanderthals?

Answer 4

• Adapted to the cold and routine heavy work as hunter gatherers operating in small nomadic groups
• Robustly built (males 1.67m & 64kg: females 1.60m & 50 kg)
• Protruding face with long nasal passages
• Large brain (1450 cc)
• thought to have Limited speech (hyoid bones; larynx structure; large hypoglossal canal)

Question 5

who did the neanderthals evolve from?

Answer 5

Evolves from H. heidelbergensis in Europe/western Asia

Question 6

what are examples of how developed neanderthals were?

Answer 6

• Practiced ritual burial
• Produced stone tools and worked wood
• found body jewellery and tools in the graves at their burial sites

Question 7

describe the two models for the evolution of homo sapiens?

Answer 7

1) the single, recent- origin model, in which Africa serves as the source of modern humans, who then replaced established populations
2) the multiregional evolution model , which balances gene flow between separate geographical populations and maintenance of regional anatomical integrity

Question 8

what is the question to differentiate the two models of homo sapien evolution?

Answer 8

do AMHs (anatomically modern humans) evolve from ergaster/erectus in Africa and then migrate or independently in Africa and Eurasia

Question 9

describe the multiregional model in more detail?

Answer 9

In the multiregional model African and Eurasian H. ergaster/erectus evolves into various species of Homo in different parts of the world (i.e. the regional differences we see today in populations of H. sapiens is a consequence of independent evolution [with some gene exchange] from H. erectus)

Question 10

describe the OOA 2 model?

Answer 10

In the “Out of Africa” II model African H. ergaster/erectus evolves into H. heidelbergensis in Africa or Europe (at least 600,000 years ago). H. heidelbergensis migrates throughout Africa and Europe giving rise to H. neanderthalensis in Europe (ca. 400,000 years ago) and H. sapiens in African (ca. 200,000 years ago). By ca. 100,000 years ago H. sapiens migrates out of Africa. These new Homo species outcompetes archaic hominins (H. erectus, H. heidelbergensis and H. neanderthalensis)

Question 11

what happened to the neanderthals?

Answer 11

Neanderthals died off in and east-west progression between 40,000 to 27,000 years ago. The occurrence of AMHs follows the same trajectory

Question 12

what are the two hypotheses for why the neanderthals died off?

Answer 12

1) competitive replacement - i.e. sapiens are better adapted
2) genocide - sapiens are aggressive and wipe out neanderthals

Question 13

what is the denisovan man?

Answer 13

• Based on 41,000 year old finger bone (+ a few other bones) from a cave in Siberia
• But recovered DNA shows it is different from both H. neanderthalensis and H. sapiens.
• It shares some DNA with some extant H. sapiens populations (as do neanderthals)
• recently also discovered a jaw bone from tibet that is also denisovan

Question 14

how are the differences between modern homo sapiens explained?

Answer 14

• homo sapiens that turned left after migrating out of Africa to then wipe out the neanderthals did some interbreeding on their way (which is why some people from Europe have some deep routed neanderthal DNA)
• homo sapiens that turned right interbred with the denisovans as some people have denisovan DNA but no neanderthal
• so there are differences between homo sapiens depending on the amount of interbreeding with cretaceous descendents

Question 15

describe the “hobbit” people of Indonesia (Homo floresiensis)

Answer 15

• Discovered in 2004 from a cave on the island of Flores,
  Indonesia.
• Dwarfed hominin from 95,000-17,000 years ago
• 1 metre tall, weighing 30 kilograms with a brain only 417 cm3.
• Used primitive tools and fire and hunted dwarfed elephants and giant lizards (Komodo dragons)—but no art.

Question 16

when did homo sapiens arrive in indonesia?

Answer 16

H.erectus lived in Indonesia from 1 Ma but H. sapiens only arrived 12,000 years ago

Question 17

hypotheses to explain the ‘hobbit’ people?

Answer 17

1) Dwarfed Hominin (evolving from H. erectus by insular dwarfing)
or
2) pathological condition (microcephaly) affecting H. sapiens.

Question 18

why is it thought that the dwarfed hominin theory is most likely?

Answer 18

• It has a primitive foot similar to H. erectus (or even H. habilis)
• Brain size measurements on dwarfed hippos suggest that the reduction in brain size is feasible.

Question 19

why was the world that the homo sapiens moved into complicated?

Answer 19

no longer just homo erectus - as the homo erectus moved around it became isolated in different areas with different environmental conditions etc causing the evolution of neanderthals, floresiensis, denisovans etc

Question 20

what is the evidence for OOA 2?

Answer 20

1) occurence of fossils (plot where they are found)

2) evidence from molecular biology

Question 21

what are the types of evidence from molecular biology?

Answer 21

• “Mitochondrial Eve” hypothesis (based on the fact that mDNA variation is lower than expected in modern humans, but greatest in Africans + molecular clock work)
• Evidence from nuclear genes and the Y chromosome
• Genetic data used to predict population dynamics among early populations
• Coalescence times (microsatellites and alu elements)
• Neanderthal and Denisovan DNA

Question 22

what is the overarching results from the molecular analyses?

Answer 22

theres more genetic diversity amongst sapiens in Africa than the rest of the world put together - suggesting sapiens diverged in Africa and then populated the rest of the world i.e. OOA 2 model

Question 23

what is there still debate over for the OOA 2 model?

Answer 23

waves of migration and numbers of individuals that populated the rest of the world

Question 24

what does neanderthal and denisovan DNA provide evidence for?

Answer 24

DNA provides definitive evidence for interbreeding. It demonstrates an interesting pattern of migration.

Question 25

what evidence does archaeology demonstrate to support OOA 2?

Answer 25

the number of tool types increased first in Africa before Asia and europe that the expansion in tool types is more recent