Transcript Human Evolution - Earth-G9

The Story of Human Evolution
From Primates to Homo sapiens sapiens
The Myth of the Biggest and
Bestest
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“survival of the fittest”
 Our cultural problem
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Stephen Jay Gould
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history of biological life =
“proliferation of enormously
varied designs subsequently
restricted to a few highly
successful, but imperfect,
forms”
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“Our world is not an optimal
place fine-tuned by omnipotent
forces of selection. It is a
quirky mass of imperfections,
working well enough (often
admirably); a jury-rigged set of
adaptations, built of curious
parts made available by past
histories in different contexts.”
Considering Evolution
 Natural Selection:
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an evolutionary process through which factors
in the environment exert pressure that favors
some individuals over others to reproduce the
next generation of the group
this pressure acts on phenotype (genes plus
environment), not genotype (DNA, genetic
makeup)
Never exact match between phenotype
and genotype
Never exact fit between organism and
environment: dynamism
Biological plasticity of individuals
Note: there are prosimians (eg lemurs), new world monkeys (eg spider monkey,
Old world monkeys (eg baboons), and apes.
Apes include gibbons, orangutans, chimps, bonobos, gorillas and humans.
99% of human DNA shared with chimps (study in Nature,Fig
8.31.2005)
8-2
Primate Tendencies
 Grasping and opposable thumbs
 Smell  sight
 mouth  hand
 brain complexity increases
 parental investment increases
 Sociality increases
Snarling mandrill
Gorilla family
gibbon
humans
chimp
Primate Social Behavior
 Wide range of social
behaviors and types of social
organization for different
species—a few examples
follow
 Male led (chimps),
female led (bonobos),
 Savanna baboons—
highly complex multi
male and female troops
 Only ape that is
monogamous—gibbon
 Apes that display wide
range of sexual
behavior—bonobos
Overview of Hominid Evolution
 Australopithecines (Lucy) 5-2 million years ago (mya)
 Gracile
 Robust
 Homo habilis (3-2 mya)
 Homo erectus (1.5 – 0.4 mya, or ?12,000ya)
 Homo sapiens (.02 mya, 200k-present)
 Homo sapiens neanderthalensis 60k
 Homo sapiens sapiens (dif places different times)
200,000k
Key Ideas
 Feedback and inadvertency
 Bipedalism
 Brain Size/complexity
 Tools, Language and Culture
 Shifts in lifestyles/diets
 Types of evolutionary change
 Graduated
 Punctuated Equilibrium
Chimp Skeleton
Human skeleton
Fig 9-5
Characteristics of
Australopithecines
 General Characteristics
 Skeleton: Bipedal, not fully upright
 Brain only slightly bigger than a chimp’s.
 Smaller canines than a chimp, bigger molars
 Hands: precision and power grip.
 Likely savanna adaptation—likely vegetarian
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Robustus has extreme savanna adaptation
Recent debate re: degree of bipedality, habitat
type
The skeleton of Lucy,
notice the bipedality
along with a relatively
small cranium and
chimp-like skull
Australopithecus
sites in Africa
Fig 9-8
On Bipedalism: Australopithecines
take steps…
 Disadvantages?
 visible to predators
 exposed underbelly
 slow
 Advantages?
 Man the hunter? (NO!)
 Woman the food
carrier
 Infant carry
Artist’s rendering of A. africanus
(interesting way in which racial ideas intervene)
Why Be Bipedal?
 Advantages, con’d
 Efficient food
procurement?
 See farther?
 Efficient long distance
travel?
 Cool brain?
 All of the above?
Artist’s rendering of A. africanus
Effect of Bipedality: inadvertency in
human evolution, 2 examples
 1. Hands are free
 tool use
 increasing tool use
leads to increasing
brain size and
complexity
 2. the birth canal
problem and its
consequence
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(evolution at work)
Pelvis structure of Humans and Chimps
Fig 9-6
From Australopithecus to Homo:
moving towards culture
 Homo habilis (the
handy man!)—(3-2
mya)
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Brain
2
 larger: 650 cm
 area of skull
indicates language
Body
 more gracile
Robust and Habilis Hung Out
 Robust australopithecines (A. boisei) and H.
habilis co-existed for at least 1/2 million years
 What happened? Why did Australopithecines
die out?
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Competitive exclusion?
Niche divergence? (natural selection is
environment specific)
Homo Erectus
 Lived 1.5 to .4 mya
 1 mya as single spp.
 Example of punctuated
equilibrium
 Significant increase in
brain size: 850-1200
 Fully erect/bipedal
Homo Erectus Lifestyle, con’d
 First use of fire
 cook
 heat
 protection against predators
 thaw out carcasses
 Evidence of “culture” or symbolic activity
 complexity of tools
 cooperative hunting
 red ochre
Illustration of an Erectus cooperative elephant hunt
Homo Erectus lifestyle, con’d
 Migration out of Africa, first time in H. history
Modern Humans, Early Homo
sapiens sapiens
 Timing of first evidence
 Africa: more than
100,000 ya
 Asia: 60,000 ya
 Europe: 35,000 ya
 Australia: 40,000 ya
 Americas: 20,000 ya
Early Modern H. s. s.
 Cultural changes
 Art (Cro Magnon)
 tools
 standardization
 distinct sets for
distinct areas
indicating cultural
diversity
Neanderthals
 Debate over where they belong in
evolutionary story
 The “cave man” …with a large brain
 Robust skeletons
 Latest research
Recent Finding from Indonesia
 2004: Tiny Homo floresiensis, 3 feet tall, resembling
H. erectus in some ways, but found with evidence of
highly developed culture, boats, etc
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Endemic island dwarfing (happens to a lot of other
large mammals on islands)
Small brain, lots of smartness…
Co-habited earth with modern humans—these finds
are from 12-18 k years ago
Cultural groups in the area have stories/legends about
“small people”
Most recent debates: some researchers argue that
these are just small modern humans
Theories of the Origins of Modern
Humans
 Two competing theories:
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Multiregional
Replacement/Out of Africa
 Multiregional/Local Continuity Theory
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evidence
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apparently intermediate fossil forms between H.
erectus and modern humans in each location
(Africa, Asia, Europe)
Theories of the Origins of Modern
Humans, con’d
 Replacement/Out of Africa-Mitochondrial Eve
Theory
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evidence
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earliest H. sapiens sapiens found in Africa
Mitochondrial and nuclear DNA
 all humans closely related, genes diverged from
single recent African origin, at about 100 kya
 Neanderthal mtDNA is not more similar to
European than any other
The Most Logical Theory: A Mix
of the two
 Independent evolution unlikely 3x
 Interbreeding/gene flow likely, migration and
movement all along
 The human thing
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migration
interbreeding
 Implications for understanding race
Questions to ask about your skulls
 What species is it?
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When did it live?
What are its key skeletal and other (?culture,
etc) features
Why is it significant?
Where does it fit on evolutionary tree leading
to Homo sapiens sapiens