Evolution of Hominine

The Big History of our Planet

– Towards The 6th threshold

“Time” Cover: What makes us Human?

A human skeleton

A male Mandrill

How different are we from other primates?

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?

EVIDENCE OF HUMAN EVOLUTION

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

Don Johanson introduces Lucy to the press: 1974

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

A careful 2011 study showed

they walked as well as modern

humans

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

Lucy’s homeland today: Hadar, Ethiopia

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

Olduvai Gorge: Tanzania The African plate is tearing apart

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

A family of gorillas

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!

Bonobo Chimpanzees Our closest relatives

only 10,000 left in the wild

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 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?

Modern Reconstructions: how accurate?

Bipedal, but otherwise

similar to modern apes

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

1964: Louis & Mary Leakey & first finds of Homo habilis

Homo habilis Modern

Reconstructions

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

Damn!

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

Homo ergaster: KNM ER 3733 found 1975, Koobi Fora, Kenya

c. 1.75 million years old

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

Homo erectus/ergaster was a traveller!

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

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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

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s

1st A

ust

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Ho

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Ho

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s/er

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1st h

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to S

. E

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sia

Au

stra

lopit

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an

d h

ab

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ex

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Nea

nd

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& H

om

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Beg

inn

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Nea

nd

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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