201907ポンプゲート h1h4 fol - Kubota...Title 201907ポンプゲート_h1h4_fol Created Date 7/29/2019 12:49:48 PM
Evolution of Hominineglobex.coe.pku.edu.cn/file/upload/201907/09/1112368613.pdf · 2019-12-17 ·...
Transcript of Evolution of Hominineglobex.coe.pku.edu.cn/file/upload/201907/09/1112368613.pdf · 2019-12-17 ·...
Taxonomy: classifying living organisms into related groups:
Pioneered by Carl Linnaeus (1707-78)
Our place in modern taxonomy: we belong to … 1. The superkingdom of Eukaryota (made of eukaryotic cells)
2. The kingdom of animalia (animals, not fungi or plants)
3. The phylum of chordata (animals with backbones)
4. The class of mammalia (mammals)
5. The order of primates (lemurs and monkeys)
6. The family of Hominidae (Humans, chimps, gorillas)
7. The sub-family of Homininae (bipedal apes)
8. The genus, Homo
9. The species, Homo sapiens
Our place in nature
The ‘Order’ of Primates (Lemurs & Monkeys)
Madagascar:
the ‘Indri’ is regarded
in Madagascar as a
reincarnated ancestor
Gorillas: at 400 lb. the
largest living primates Galago, or
‘bush baby’, Africa
Macaque, N. Africa
Tarsier: Philippines &
Indonesia
What features do primates share?
• Mammals
– Embryos develop in the womb
• Tree-dwelling, so they need:
– Dexterous hands (and feet)
– Stereoscopic vision
– A large brain to process visual information
Our closest living relatives: The ‘family’ of Hominidae,
‘Great Apes’
Orang-Utan
Gorilla
Chimpanzee
Darwin guessed (rightly) that our
ancestors evolved in Africa, where our
closest relatives live
Large, intelligent
primates,
with no tails
Homo sapiens
We are also very different
• How? The 1.6% DNA difference matters!
– Includes 30 million ‘point mutations’
– Affecting most of our 30,000 genes
• Which difference makes us so strange?
– Our history has been utterly different
– We have become more powerful than any other species on earth
– Why? And How?
Four types of evidence on human evolution
1. Archaeology: bones & remains can tell us about physiology & lifeways
2. Primatology: Studies of modern primates can help us understand their social life
3. Genetics: Genetic comparisons show relationships between species
4. Climate Change: Evidence of climate change & its impact
1) Studying bones & Remains: Lucy, about 40% complete
Found by Donald Johanson in
Ethiopia in 1974
Could you tell if Lucy walked on
two legs or four? How?
1) Look where the backbone
enters the skull
2) Look how the leg bones
join the hip
She was bipedal, but may
have preferred climbing
Confirmation that Australopithecines were
bipedal? Australopithecine
footprints: Laetoli, Tanzania
These footprints, left in the still soft
lava of a volcano, have been dated to
3.6 million years ago. They were
found by Mary Leakey in 1978
What else can we tell about Lucy?
Measurements
– About 3.5 feet tall
– Her skull was slightly larger
than a chimp’s
Modern Dating techniques
– She lived 3.2 million years
ago
Hadar, Ethiopia
African Rift
Valley Other important sites
for human evolution?
Olduvai Gorge
Laetoli footprints
How a rift valley is formed
The beginning of a divergent plate margin
Rising magma
driving plates
apart
This is how the Atlantic Ocean began
Studying what Hominines left behind
• Stone tools give clues about – How hominines thought [planning? foresight?
right-handedness?] – What they ate [microscopic studies of edges] – What they ate tells much about how they lived
Oldowan tools, from c. 2.5
million years ago, products of
Homo habilis
The sharp chips flaked off
them may have been as
important as the “axes”
2) 2nd type of evidence: Primatology: Studying modern primates
Can tell us a lot about the abilities and social life
of our closest relatives
Tool making?
Language?
Social competition?
Jane Goodall
• Pioneered the study of
primates in their natural
environments
• Began studying
chimpanzee communities
at Gombe in Tanzania in
the 1960s as a student of
Louis Leakey
Jane Goodall
working in Olduvai
Gorge
Dian Fossey
• Studied gorillas in
Rwanda
• Wrote “Gorillas in
the Mist”
• Murdered in 1985,
probably by gorilla
poachers
Studying modern primates
Mother & daughter Orang-Utan
Can tell us much about the social life
of our Hominine ancestors
Social learning in primates? Can they learn from each other?
To a limited extent: yes
Sept 2006:
• A troop of chimpanzees learning how to safely cross a road
• Dominant adults took up protective positions in front and at the rear
3) Comparing genes can show relationships between organisms
• We share 98.4% of our DNA with chimps
• In the 1980s, researchers showed it takes c. 5-7 million years for such a difference to evolve
• i.e., c. 5-7 million years ago, humans and chimps had a common ancestor
The statistical nature of evolutionary change
• This conclusion depended on seeing that much genetic change is statistical – Only 3% of our genome produces proteins & is
directly subject to natural selection
– Some parts may play no role, so they can change randomly
– The rest probably controls our bodies indirectly by switching genes on and off
• How these ‘non-coding’ genes work is an important new research frontier!
Too human for comfort? The smoking chimpanzee
Ai Ai is 27 years old
and has been
smoking for 16 years
since her partner died
Zookeepers in China
are helping her kick
the habit
4) Climate change
• Rapid climatic changes in the last few million years
• Favored generalist species
• Capable of surviving in rapidly changing climates and environments
• Species such as
– Humans
– Weeds
Mark Maslin, Global Warming, p. 44
CLIMATE CHANGE OVER 800 Mys
• We live in a peculiarly cold era
• Temperatures have been falling for 100 Mys
• Mainly because of changes in plate tectonics, e.g.
• Union of Americas creation of cold water
current around Antarctica
Last 100 Mys Cambrian era
Falling temperatures
Last 100 Mys
Today Pangaea
CO2 levels: The Last 800,000 Years Data from the European Project for Ice Coring in Antarctica, Epica.
Humans Appear
Last Ice Age
• A fairly regular cycle of ice ages
• About 100,000 years of ice age
• About 10,000 years of warmer, “interglacial” climates
From the Vostok Ice Core, Antarctica
The Anthropocene?
9 Coldest phases ….
The Story of Hominine Evolution
• The ‘sub-family’ of Hominines
– Bipedal great apes
• Appeared about 7 million years ago
– What’s the evidence for that date?
– Perhaps 30 or more species
– All but one now extinct Which survives?
The shape of human evolution: a bush with many lost limbs
Hominine line Chimp line
Common ancestors of
chimps and humans c. 7
million years ago
Australopithecines
Homo habilis
Homo erectus/ergaster
Neanderthals
Most branches have died out.
Humans and Chimps are the
only survivors of a large
evolutionary ‘radiation’.
Chimps &
Bonobos Modern Humans
Three Main Stages in Hominine Evolution
A brief history of hominine evolution since the split from the chimp line, 6-8 Mys ago
– We focus on three main groups of species
1. Genus: Australopithecines
2. Species with variants: Homo habilis
3. Species with variants: Homo erectus/ ergaster
A) Australopithecines: e.g. Lucy
“Australopithecus” is a genus that includes several distinct species. Its members are:
•Bipedal
•About as tall as chimps
•Brains same size as those of chimps
•Little evidence of tool use or language
•c. 5 million to 1 million years ago
Bipedalism: the first major difference from chimps
• Bipedalism (not braininess!) is the defining feature of hominines
– Walking on two legs as the norm
• Why? Not sure
– Maybe to enable tool use?
• Bipedalism comes before tool use
– More efficient travel in savanna lands?
B) Homo habilis: 1st species of a new genus, ‘Homo’, from c. 2.5 MY ago
The genus ‘Homo’ includes us
Homo habilis had:
• Larger brains (perhaps because they ate more meat or cooked food?)
• Made tools (which helped them get meat)
• Once thought to be the first ‘humans’
Now thought to be much
more ape-like
Louis Leakey holding a Homo habilis skull
1960s
• Leakey saw tool use as a unique feature of humans
• So classified habilis as the 1st human
To the right: an
Australopithecine skull
Tool Use: No longer seen as key to humanity: many primates use tools
2005: For the first time
Gorillas observed using tools in the wild
Efi uses a stick to get across a swamp
C) Even closer: Homo erectus/ergaster
Skull of a
female
Homo
erectus
• From c. 1.9 million years ago
• As tall as us
• Brains almost as large as ours
• Migrations out of Africa
• Perhaps use of fire?
Modern
reconstructions
1.5 M-year old footprints of Homo erectus
• Fossilized, found in Kenya, 2009
• They walked almost exactly like us
• Which may explain why they travelled further than any earlier hominines
Why did brains get bigger?
• Brains are costly: – 3% of body weight but need 20% of its energy
– Large heads make childbirth dangerous
• Is cooking the key? Richard Wranghams’s idea – Evidence that Homo erectus used fire
– Cooked foods are partially digested
– Pre-digestion made it easier to use high energy foods such as meat
– Support for this idea from changing dental patterns
But even erectus/ergaster didn’t change much
They made ‘Acheulian’ stone tools
More skillfully made than the stone
tools of Homo habilis, but
Didn’t change much over 1 million
years
No sign of major technological
innovation
What distinguishes us from other hominines?
• A = Tool Use
• B = Art, religion and culture
• C = Language
• D = Something else
A frustrating conclusion
• Hominines more like us
• But no fundamental breakthrough
• A problem: – Evolution can explain why we are so
similar to other animals
– Can it also explain why we are so different?
A TIME-CHECK: Timeline 4: 65 million years
How do you get from early primates to the Cassini satellite?
1st fossil primates
Earliest apes
1st hominines
Lucy
The Evolution of Primates
Next Timeline
The last 7 MYs
MILLIONS OF YEARS BEFORE PRESENT DAY
7 6 5 4 3 2 1 0
Ear
lies
t re
mai
ns
of
bip
edal
ho
min
ine
Ard
ipip
ith
ecus
ram
idu
s
1st A
ust
ralo
pit
hec
ines
Ho
mo
ha
bil
is
Ho
mo
ere
ctu
s/er
gast
er
1st h
om
inin
e m
igra
tio
ns
to S
. E
ura
sia
Au
stra
lopit
hec
ines
an
d h
ab
ilis
ex
tin
ct
Nea
nd
erth
als
& H
om
o s
ap
ien
s
Beg
inn
ing o
f la
st I
ce A
ge
Nea
nd
erth
als
& e
rect
us
exti
nct
Earliest hominines
Ardipithecus ramidus
1st Australopithecines
Homo habilis
Homo erectus/ergaster
Modern humans
Very few
fossils from
this period
Lucy
HOW FAST THINGS HAPPENED! Hominine evolution over 7 MYrs
FROM GREAT APES TO THE CASSINI SATELLITE
All of human history lies between these two arrows
HOW FAST THINGS HAPPENED! Hominin evolution over 7 MYrs
MILLIONS OF YEARS BEFORE PRESENT DAY
7 6 5 4 3 2 1 0
Ear
lies
t re
mai
ns
of
bip
edal
ho
min
ine
Ard
ipip
ith
ecus
ram
idu
s
1st A
ust
ralo
pit
hec
ines
Ho
mo
ha
bil
is
Ho
mo
ere
ctu
s/er
gast
er
1st h
om
inin
e m
igra
tio
ns
to S
. E
ura
sia
Au
stra
lopit
hec
ines
an
d h
ab
ilis
ex
tin
ct
Nea
nd
erth
als
& H
om
o s
ap
ien
s
Beg
inn
ing o
f la
st I
ce A
ge
Nea
nd
erth
als
& e
rect
us
exti
nct
Earliest hominines
Ardipithecus ramidus
1st Australopithecines
Homo habilis
Homo erectus/ergaster
Modern humans
Very few
fossils from
this period
Lucy
FROM GREAT APES TO THE CASSINI SATELLITE
All of human history lies between these two arrows