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Human Evolution
Our biological history
What is evolution?
Evolution is change
 Biological evolution is change in the
properties of a population over time

Why ?
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We discuss human evolution because:
– Speculation about human history and the natural
world plays an important role in many societies
– Culture is an expression on top of our biological base
– Biology and culture are intertwined: complex brains
have evolved with complex social organization
– Our evolutionary history is part of what it means to
be human
Natural Selection

Set of simple patterns that work together to
change a population over generations
– Variation – there is variation among members of
a species
– Mutation – variation arises from random
changes in genetic material
– Gene flow – when individuals move from place
to place and mix genes in new gene pools, this
adds to variation
– Genetic drift – in isolation or disaster, whatever
random genes made it through will be passed
on to future generations
Natural Selection

Set of simple patterns that work together
to change a population over generations
– Varied reproductive success –
 Not all individuals survive to reproduce
 Those that do will pass traits on to offspring
 “survival of fittest”
Our Closest Relatives
25 – 20 mya LCA with monkeys
 13mya LCA with great apes
 7mya LCA with chimpanzees
 All primates originated as tree dwellers

– Opposable thumbs
– Depth perception
Primate Social Life
Live in social groups with strong mother/infant
bond
 Learn by mimicking mother
 Learn by playing – refine physical and social skills
 Dominance hierarchies reduce conflict

Tool Use in Primates

Vary by group, therefore learned
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Macaques wash food
Chimpanzees use hammerstone to break nuts
Chimpanzees use sticks to fish for termites
Chimpanzees use leaves as sponges
Evolution of Humans

Bipedalism differentiates us from other
primates
– Requires restructuring of feet, legs, hips, spine
and skull
– Frees hands to carry objects
– Improves view of surroundings
– Can walk efficiently over long distances
Evolution of Humans

Australopithecines 4 mya to 1 mya
– Gracile
 3.5–5 feet tall, 65-100 pounds, brains 1/3 size of ours
 Eastern and southern Africa
 Omnivores – fruit, vegetables, insects, small animals
– Robust
 Larger, much heavier skulls and jaws, bigger teeth
 Adapted for chewing heavy, coarse material like
grasses, leaves and roots
Evolution of Humans

Australopithecines 4 mya to 1 mya
– Gracile
– Robust

Homo
– Homo habilis
 Larger brains, smaller teeth
 Oldowan stone tools
 Omnivores, hunted small animals, scavanged large
 May have migrated to Europe and China
Evolution of Humans

Australopithecines 4 mya to 1 mya
– Gracile
– Robust

Homo
– Homo habilis
– Homo erectus
 Larger body and brain – in modern human range
 Use of tools and fire
 Omnivores, including hunting large animals
 Found in Africa, Asia and Europe
Evolution of Humans

Australopithecines 4 mya to 1 mya
– Gracile
– Robust

Homo
– Homo habilis
– Homo erectus
– Homo sapiens
Evolution of Humans

Homo erectus 1.8mya – 100kya
Neanderthals 130kya – 35kya
 Modern Humans 195kya
 Are Neanderthals modern humans of a
separate species?

– Replacement model
– Multiregional model
– Hybridization model
Homo sapiens Culture

Varied and efficiently made stone tools
– Compound tools – ax head bound to handle
– Atlatl – handle that increases power in spear throwing
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Symbolic and artistic artifacts
– Venus figurines – 30 – 20kya, 40 figures
– Cave paintings

Domestication of plants and animals
– When Ice Age populations declined people turned to
domestication
– Dogs domesticated 10 to 14kya
– Rye farming begins in the Middle East 13kya