Transcript 3680consciousnessevol4x

Human evolutionary history
other Old World monkeys
‘apes’ and humans
upright posture
loss of tail
increased brain size
Humans show similarities with ‘apes’ (gibbons, orang, gorilla, chimps)
• shared derived traits: large brain, no tail, more upright posture
Human evolutionary history
gorilla
chimps
human
gorilla
knucklewalking
morphology
chimps
human
?
similarities in
teeth, skull, genitals
Which are closer: gorilla & chimps or humans & chimps?
• are traits shared derived versus convergent / lost?
Human evolutionary history
gorilla
chimps
human
gorilla
knucklewalking
morphology
chimps
human

common ancestor
~5 million yrs ago
DNA similarities
similarities in
teeth, skull, genitals
Molecular data suggests chimps and human are close relatives
Human evolutionary history
other Old World
gibbons orang gorilla chimps human
monkeys
many unique traits
similarities in teeth,
skull, genitals
brow ridge
loss of some hair
skull elongation
upright posture
loss of tail
increased brain size
Humans’ closest living relatives are chimpanzees
• shared derived traits: morphological: skull, teeth, genitals
behavioral: hunting, tool use, social behaviors
?
Millions of years ago
Australopithecus
robustus
Homo
ergaster
Australopithecus
africanus
Homo
sapiens
Australopithecus
afarensis
Homo
neanderthalensis
Homo
erectus
Australopithecus
anamensis
Australopithecus
boisei
Homo
habilis
Ardipithecus
ramidus
Ardipithecus
ramidus kadabba
Orrorin tugenesis
Figure 19.3
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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
19.4 Upright posture evolved well before our
enlarged brain
• Australopithecines
had relatively small
brains
– This indicates that
bipedalism preceded
the evolution of the
enlarged brain
– Bipedalism is a basic
human trait
Figure 19.4
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
A brief history of human
brains
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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
Evolution
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?
Evolution
Evolution
The Mating Mind
Geoffrey Miller
Why do we have
big brains?
Evolution of the brain

Brain is expensive


Evolution requires you to pay your way as you
go;
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
brain energy use as a percent of resting body usage
 most vertebrates: 2 to 8%
 apes and some monkeys: 13%
 Humans: 20%
no investment for 50,000 years in the future
What was the brain used for in the mean time?
Forms of Darwinian Selection
 Natural


"nature red in tooth and claw"
competition for food and for staying alive
 Sexual

selection
selection
Competition for mates
Sexual Selection

Female mate selection

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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?
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hidden estrous requires multiple copulations
male investment in childrearing??
or just ongoing courtship
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
Advertising fitness
 Fitness
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Genetic quality
Health and nutrition
Sports

what do you win? - status
 Conspicuous
consumption
 Conspicuous generosity

not kinship or reciprocal altruism
Theory of mind