the story of human evolution
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The Story of Human Evolution. From Primates to Homo sapiens sapiens. The Myth of the Biggest and Bestest. “survival of the fittest” Our cultural problem Stephen Jay Gould - PowerPoint PPT PresentationTRANSCRIPT
The Story of Human Evolution
From Primates to Homo sapiens sapiens
The Myth of the Biggest and Bestest “survival of the fittest”
Our cultural problem
Stephen Jay Gould
history of biological life = “proliferation of enormously varied designs subsequently restricted to a few highly successful, but imperfect, forms”
“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: 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
Fig 8-2
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, 8.31.2005)
Primate Tendencies
Grasping and opposable thumbs Smell sight mouth hand brain complexity increases parental investment increases Sociality increases
Snarling mandrill
Gorilla familygibbon
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
Fig 9-5
Chimp Skeleton Human skeleton
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
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 andchimp-like skull
Fig 9-8
Australopithecus sites in Africa
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 (evolution at work)
Fig 9-6
Pelvis structure of Humans and Chimps
From Australopithecus to Homo: moving towards culture
Homo habilis (the handy man!)—(3-2 mya) Brain
larger: 650 cm2
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? 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 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:
Multiregional Replacement/Out of Africa
Multiregional/Local Continuity Theory evidence
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 evidence
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
migration interbreeding
Implications for understanding race
Questions to ask about your skulls
What species is it? 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