Human Evolution Our biological history

What is evolution? Evolution is change Evolution is change Biological evolution is change in the properties of a population over time Biological evolution is change in the properties of a population over time

Why ? We discuss human evolution because: 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 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 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 25 – 20 mya LCA with monkeys 13mya LCA with great apes 13mya LCA with great apes 7mya LCA with chimpanzees 7mya LCA with chimpanzees All primates originated as tree dwellers All primates originated as tree dwellers –Opposable thumbs –Depth perception

Primate Social Life Live in social groups with strong mother/infant bond Live in social groups with strong mother/infant bond Learn by mimicking mother Learn by mimicking mother Learn by playing – refine physical and social skills Learn by playing – refine physical and social skills Dominance hierarchies reduce conflict Dominance hierarchies reduce conflict

Tool Use in Primates Vary by group, therefore learned Vary by group, therefore learned –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 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 Australopithecines 4 mya to 1 mya –Gracile  3.5–5 feet tall, 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 Australopithecines 4 mya to 1 mya –Gracile –Robust Homo 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 Australopithecines 4 mya to 1 mya –Gracile –Robust Homo 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 Australopithecines 4 mya to 1 mya –Gracile –Robust Homo Homo –Homo habilis –Homo erectus –Homo sapiens

Evolution of Humans Homo erectus 1.8mya – 100kya Homo erectus 1.8mya – 100kya Neanderthals 130kya – 35kya Neanderthals 130kya – 35kya Modern Humans 195kya Modern Humans 195kya Are Neanderthals modern humans of a separate species? Are Neanderthals modern humans of a separate species? –Replacement model –Multiregional model –Hybridization model

Homo sapiens Culture Varied and efficiently made stone tools Varied and efficiently made stone tools –Compound tools – ax head bound to handle –Atlatl – handle that increases power in spear throwing Symbolic and artistic artifacts Symbolic and artistic artifacts –Venus figurines – 30 – 20kya, 40 figures –Cave paintings Domestication of plants and animals 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