Human evolutionary history
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Transcript of Human evolutionary history
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Human evolutionary history
Humans show similarities with ‘apes’ (gibbons, orang, gorilla, chimps)
• shared derived traits: large brain, no tail, more upright posture
other Old World monkeys ‘apes’ and humans
increased brain sizeloss of tail
upright posture
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Human evolutionary history
Which are closer: gorilla & chimps or humans & chimps?
• are traits shared derived versus convergent / lost?
human
similarities inteeth, skull, genitals
gorilla
?chimps
human
knucklewalkingmorphology
gorilla chimps
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Human evolutionary history
Molecular data suggests chimps and human are close relatives
human
similarities inteeth, skull, genitals
gorilla
chimps
human
knucklewalkingmorphology
gorilla chimps
DNA similarities
common ancestor~5 million yrs ago
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Human evolutionary history
Humans’ closest living relatives are chimpanzees
• shared derived traits: morphological: skull, teeth, genitals behavioral: hunting, tool use, social behaviors
other Old Worldmonkeys chimps
increased brain sizeloss of tail
upright posture
gibbons
skull elongationloss of some hair
brow ridge
orang gorilla human
similarities in teeth,skull, genitals
many unique traits
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 19.3
Mill
ions
of y
ears
ago
Australopithecusanamensis
Ardipithecusramidus
Ardipithecusramidus kadabba
Orrorin tugenesis
Australopithecusafarensis
Australopithecusafricanus
Australopithecusrobustus
Australopithecusboisei
Homoergaster
Homohabilis
Homoerectus
Homoneanderthalensis
Homosapiens
?
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The earliest hominids were a diverse group– Various species of Australopithecus date
from about 4 to 1 million years ago– Our own species, Homo sapiens, is the
only hominid that has not become extinct
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Australopithecines had relatively small brains – This indicates that
bipedalism preceded the evolution of the enlarged brain
– Bipedalism is a basic human trait
19.4 Upright posture evolved well before our enlarged brain
Figure 19.4
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A brief history of human brains Neandertals - large brains 200,000 years ago Modern homo sapiens (and their brains) evolved ~
100,000 years ago in africa Most toolmaking came tens of thousands of years later Agriculture and the rapid growth of human
populations came 90,000 years later
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Evolution
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Evolution of mind The mind evolved just like the rest of the
body. The principle is clear, but the details are
highly contentious What might have been a driving force for
human minds?
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Evolution
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Evolution
The Mating MindGeoffrey Miller
Why do we have big brains?
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Evolution of the brain Brain is expensive
brain energy use as a percent of resting body usage most vertebrates: 2 to 8% apes and some monkeys: 13% Humans: 20%
Evolution requires you to pay your way as you go;
no investment for 50,000 years in the future What was the brain used for in the mean time?
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Forms of Darwinian Selection
Natural selection "nature red in tooth and claw" competition for food and for staying alive
Sexual selection Competition for mates
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Sexual Selection Female mate selection
asymmetry of costs lead to male display and female selection
male birds generally have the plumage male humans have orgasm relatively easily, females less
easily Females are choosing
but also male selection in humans - why? hidden estrous requires multiple copulations male investment in childrearing?? or just ongoing courtship
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The Handicap Principle Handicap’s provide useful signalsthat
the male is fit Handicaps in human
Aside: the immorality of handcap Sexual selection causes runaway "fads"
peacock's feathers
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Advertising fitness Fitness
Genetic quality Health and nutrition
Sports what do you win? - status
Conspicuous consumption Conspicuous generosity
not kinship or reciprocal altruism
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Theory of mind