Human Evolution - The Homo Genus

Question 1

Fossil Basics - Trace Fossils (Ichnology)

Answer 1

• Footprints
• Coprolites, tracks, trails, nests

Question 2

Fossil Basics - Periminerilsation + Petrification

Answer 2

• Chemical process
• Minerals replaced

Question 3

Taphonomy

Answer 3

• How an animal becomes fossilised and what processes mean it will/won’t

Question 4

Why are some bones more commo than others?

Answer 4

• Teeth is very common due to very solid material that survives trampling and wethering
• Smaller bones are less likely to be fossilised as they can be crushed

Question 5

Why are fossils not found everywhere?

Answer 5

• Human fossils aren’t everywhere due to habitat e.g. rainforests

Question 6

Stratigraphy

Answer 6

• How layers of the earth is formed/what they are made of

Question 7

Dating

Answer 7

top layer = new, bottom = older?
- not as straightforward as some things sink/ humans bury things in holes / in caves, there is a lack of banding due to flooding etc.

Question 8

How do you determine a species? - Splitters

Answer 8

Different species unless there is a convincing reason to unite the

• Variation = new species

Question 9

How do you determine a species? - Lumpers

Answer 9

Same species unless there is a convincing reason to divide them

• Intra-species variation normal e.g. age, sex, disease, genetic variation

Question 10

Interbreeding

Answer 10

• Different + related species can interbreed
• Often infertile but not always (takes 2 million years of separation from a common ancestor)

Question 11

Hybrid zones

Answer 11

10% of primate species engage in cross-species hybridization

• can result in a new species

Question 12

Fossil remains are limited

Answer 12

• Complete skeletons are incredibly rare + can be difficult to identify
• Usually find a mix of fragmentary bones + teeth
• Often impossible to link cranial + post cranial elements

Question 13

Original definition of Homo genus (compared to previous genus)

Answer 13

• Small, modern teeth compared to ancestors’ large teeth in homo fossil record
• Bipedal
• Tool use - thought this meant intelligence so they are more human
• Brain size

Question 14

Small teeth not exclusive to Homo genus

Answer 14

• Found before homo species
• Older species (Australopithecus sediba (MH2)) had smaller teeth than homo genus

Question 15

Being bipedal not exclusive to Homo genus

Answer 15

• Upright posture/ bipedality goes back 7 million years with Sahelanthropus tchadensis

Question 16

Tool use not exclusive to Homo genus

Answer 16

• Use of tools predated Homo genus (~2.8 Mya)
• ~3.3 Mya ‘Lomekwian’ : Kenyanpithecus platyops
• ~3.4 Mya cut marks on bones: Australopithecus afarensis

Question 17

Bigger brains not exclusive to Homo genus

Answer 17

• Homo habilis = 500cm^3 on low end while Paranthropus robustus = 550cm^3
• There was a trend towards bigger brain vol over times
• However, variations with ranges overlapping between ancestors of another genus + more modern homonids

Question 18

Is our definition of Homo wrong & why all these problems with the Homo genus?

Answer 18

• Homo habilis was found with old definition of homo genus but with a small brain
• Debate if it counts as a homonids e.g. they used tools a lot, small teeth, but more like the species before than species later

Question 19

Genetics + interbreeding : H. sapiens

Answer 19

Interbred with:
- Denisovans (Melanesians & Aboriginal Australians)
- H. neanderthalensis (Eurasians + Africans)
- Also with unknown archaic European pop. + African pop. (in areas with lack of fossil record e.g. West Africa)

Question 20

Genetics + interbreeding : H. neanderthalensis & Denisovans

Answer 20

Interbred thousands of years ago:
- Female remains from around 90 kya found to have a N mother + D father

Question 21

Link between climate + evolution of homonids

Answer 21

• Large climatic fluctuations when homo genus evolved

If climate is variable/ severe, you might:
- Die out
- Move to a new area
- Adapt to diff. conditions

Hominin variability = environmental variability

Question 22

Homo mass migration out of Africa however…

Answer 22

• Absence of evidence is not evidence of absence
• Lack of fossils in regions doesn’t mean there are no homonids

Question 23

Did Homo habilis leave Africa? - Theories

Answer 23

• Inefficient energetics as they were shorter = shorter strides so more energy not as efficient at moving
• Challenging Northern African habitat - dry + desert condition
• Were scavengers - didn’t actively hunt

However, no evidence that they left Africa

Question 24

Were Homo erectus the first global species?

Answer 24

Originally considered all individuals:
- Energetically efficient, tall, bipeds
- Had increased brain size

• Known to be morphologically variable
• Behaviourally more capable/adaptable since they’re active hunters - can make tools to problem solve
• Makes it easier to eat while migrating not relying on finding food

Question 25

Violence between modern humans and neanderthals

Answer 25

• Evidence of interspecies aggression from bone injuries
• But, highly unlikely this caused Neanderthal extinction
• Neanderthals also had tools + were the main species at the time
  ==> really unlikely to be extinct by violence

Question 26

Pathogens from modern humans to Neanderthals?

Answer 26

• Happened when modern humans made it to Eurasia
• Neanderthals had no defense as it was new to them
  => Modern humans did also pick up things from Neanderthals
• Tapeworms, TB, stomach ulcers + types of herpes may have weakened the Neanderthal pop.
• No evidence that this alone killed Ns off

Question 27

Did climate change, small populations and competition kill of Neanderthals?

Answer 27

• Neanderthals were well adapted to cold
  => but climate got colder around time they died out
• Could move south for warmer cond. but humans were migrating out of the south
  => had similar niches so more competition
• Lived in small populations so less flow of genetics and less genetic diversity (inbreeding could happen) unlike homo sapiens

Question 28

Did interbreeding kill off Neanderthals?

Answer 28

• DNA indicates this happened
• However, may have not died out but the species joined with homo sapiens
• 40,000 years ago, 6-9% of human genome came from N