Lecture 5- Human movement models only

Question 1

What are the four main models for human evolution?

Answer 1

1. Out of Africa
2. Multi regional
3. leaky replacement
4. assimilation

Question 2

what was the first hominid species to leave Africa? when?

Answer 2

homo erectus. 1.8 ma

Question 3

explain the out of Africa model for human evolution

Answer 3

• anatomically modern humans evolved within Africa 200-100ka
• they then migrated out of Africa
• they replaced the regional descendants of Homo erectus,
• humans began evolving in different continents 60ka
• if correct, modern human populations are more closely related than in the multiregional model

Question 4

which model has humans more closely related?

Answer 4

out of Africa

Question 5

when did humans begin evolving in separate continents according to the out of Africa model?

Answer 5

60ka

Question 6

why does mitochondrial DNA from neanderthals support the out of Africa model

Answer 6

it shows clear and distinct evolutionary lines between neanderthals and AMH. This shows limited interbreeding between the two, which supports the theory that they evolved separately in out of Africa

Question 7

where were the fossils that support out of Africa found? how do they support it?

Answer 7

Fossils found in the KIBISH formation in ethipoia found an AMH aged 195000 years. this supports the theory than anotomically modern humans evolved in Africa first, 200ka

Question 8

how does the geographical study “comparison for various geographical regions” support out of Africa?

Answer 8

This study used Y chromosome evidence to show that modern humans diverged from a singular modern ancestor 60ka, which supports the theory that diversifying began 60ka

Question 9

three pieces of evidence for the out of Africa model

Answer 9

• strict evolutionary lines from neanderthals
• y chromosome evidence shows divergence from a common ancestor 60ka
• kibish fossil in ethiopia

Question 10

explain the main points of the multiregional model

Answer 10

• homo erectus left Africa 1.8 Ma
• anatomically modern humans then evolved OUTSIDE of Africa in many different regions
• interbreeding occurred between the different populations, creating observed similarities between modern humans
• humans are less closely related than in out of Africa model

Question 11

how does the multiregional model account for similarities and differences in modern humans

Answer 11

similarities= interbreeding between different populations
differences= majority of the breeding occurred in allopatry, giving different phenotypes

Question 12

who is mitochondrial eve and how does she support the multiregional model

Answer 12

shes the most recent common ancestor to all living humans, found in east Africa.
-she shows that diversification into new species occurred 150ka- not 60ka like out of Africa suggests.

Question 13

how did a 2008 study in nature model support the multiregional model?

Answer 13

-found a hominina fossil in spain dating to 1.2-1.1ma. suggests humans left Africa a lot earlier than 200-100ka

Question 14

two pieces of evidence supporting the multi regional model?

Answer 14

• mitochondria eve

- hominina fossil in spain

Question 15

how are out of africa and the assimilation model similar?

Answer 15

both state than anatomically modern humans evolved within Africa, and left 100-200ka

Question 16

outline the assimilation model

Answer 16

• humans evolved in Africa and left 200-100ka
• emphasises assimilation (interbreeding) between other hominins as AMH spread globally, primarily breeding with neanderthals and homo erectus
• those who remained in Africa have no neanderthal DNA

Question 17

does the assimilation favour replacement?

Answer 17

no, it states assimilation with other hominins and the evolution of new species from that point, not replacement of

Question 18

what is the neanderthal evidence for the assimilation model? How?

Answer 18

science 2011 sequenced the entire neanderthal genome. they found that neanderthals share 1-4% DNA with modern humans in EUROPE and ASIA. However, the lack of neanderthal DNA in African populations supports the theory that AMH evolved there first.

Question 19

outline the leaky replacement model

Answer 19

-homo species evolved in Africa. An ancestral species migrated to Europe whereas some stayed in Africa
-homo erectus in Europe diverged to form Neanderthal and Denisovans
-at this time AMH evolved in Africa,when they left Africa approx 200-100ka, they assimilated with neanderthals(at a small rate)
human populations containing neanderthal DNA migrated west to mate with Denisovans forming modern day melanesians

Question 20

in leaky replacement, how did modern day Europeans and Asians form?

Answer 20

From the interbreeding of AMH and neanderthals

Question 21

How did modern day Melanesians evolve in the leaky replacement model?

Answer 21

hybridised neanderthal and AMH’s migrated west to the isolated denisovan genome, they then mated forming a population with 2.5% neanderthal DNA and 5% Denisovan

Question 22

in the leaky replacement model, what did homo erectus diverge into?

Answer 22

Neanderthals and denisovans

Question 23

what is the evidence for leaky replacement?

Answer 23

• fossilised finger found in Siberia dating to 30-50Ka ago. this species was different to AMH but similar to Neanderthal (a denisovan)
• “Denny” skeleton found in 2018. 40% neanderthal and devisovan dna. clear evidence of interbreeding

Question 24

Why is mitochondrial dna a good indicator of evolution?

Answer 24

It’s slow changing and consistent