Evolution

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Evolution Mon, Wed Fri 200 250
pm Spring Semester 2006
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Evolution 1 2006 Spring
Primates Humans
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Evolution 2 2006 Spring
Primate evolution
-gt an order of mammals -gt adaptations indicate
arboreal ancestry - limbs can move in
various directions - grasping power of hands
and feet - slip-resistant cutaneous ridges
- flexible spine
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Evolution 3 2006 Spring
Primate evolution
-gt highly developed brain -gt long postnatal
parental care -gt few offspring -gt long learning
periods to cope with complex environment and
social system
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Evolution 4 2006 Spring
Primate classification

• 230 species
• Two suborders
• Prosimians
• lower primates
• -gt long snout, claws, lateral facing eyes,
• small body, nocturnal
• Anthropoids
• monkeys, apes, humans
• -gt short-faced, forward directed eyes,
  larger,
• more complex brain

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Evolution 5 2006 Spring
20-1
Primate classification
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Hominoidea (Superfamily)
Evolution 6 2006 Spring
20-1
Primate classification
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Evolution 7 2006 Spring
Primate classification
Hominoids -gt adaptations to brachiating arboreal
locomotion - more erect posture -
flexible limbs - shorter spine -gt
adaptations to ground dwelling existence -
broader and larger pelvis to support
vertical weight
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Evolution 8 2006 Spring
Human-ape comparison
humans have -gt bipedal terrestrial
locomotion -gt hind limbs that are longer
relative to forelimbs -gt hands are free from
supporting the body (can be used for
manipulation) -gt larger brain -gt less body hair
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Evolution 9 2006 Spring
Human-ape comparison
Anatomical striking resemblance
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Evolution 10 2006 Spring
Human-ape comparison
Similarities in posture and facial expression
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Evolution 11 2006 Spring
Human-ape comparison
Molecular comparisons Chimpanzees and humans
are 97 98 alike!
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Evolution 12 2006 Spring
Fossil Record
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Evolution 13 2006 Spring
The Australopithecines
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Evolution 14 2006 Spring
The Australopithecines
Australopithecus afarensis gt Lucy (found in
Ethiopia) -gt small muscular body -gt adult brain
volume 450 cc (midway between chimp and
gorilla) -gt 3.5 4 feet high -gt longer arms than
humans -gt bipedal
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Evolution 15 2006 Spring
The Australopithecines
Australopithecus robustus ( southern ape) -gt
walked bipedally accompanied with
climbing -gt more or less herbivorous diet -gt
brain volume 550 cc (due to increased body
size rather than intelligence)
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Evolution 16 2006 Spring
The Australopithecines
More evidence for bipedal locomotion Fossil
footprints -gt 3.7 mio years old -gt preserved
under a layer of volcanic ash at
Laetoli (Tanzania) -gt two individuals -gt path
of more than 70 feet http//www.mnh.si.edu/anthro/
humanorigins/ha/laetoli.htm
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Evolution 17 2006 Spring
The Australopithecines
-gt genus Homo descended from a population of
australopithecines -gt or not? -gt Orrorin is
challenging this theory
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Evolution 18 2006 Spring
Bipedalism
How and why did it originate?
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Evolution 19 2006 Spring
Bipedalism
How and why did it originate? 1) Improved food
acquisition -gt patchy grassland
environments -gt enabled walking longer
distances for foraging trips -gt
invention and use of food gathering tools gt
byproduct of reduced forelimb usage for
locomotion
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Evolution 20 2006 Spring
Bipedalism
How and why did it originate? 2) Improved
predator avoidance -gt enhances height -gt
increased field of view -gt see over tall
grass in grasslands -gt still maintain
tree-climbing ability
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Evolution 21 2006 Spring
Bipedalism
How and why did it originate? 3) Improved
reproductive success -gt home base strong
family bonds -gt male gathered food and
carried it to home base -gt reduced need for
female to be mobile advantages -
more constant social relationships - reduced
infant injury - more care for offspring,
more offspring
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Evolution 22 2006 Spring
Bipedalism
How and why did it originate? 3) Improved
reproductive success preadaptations -
sexual bonding - year-round copulations -
concealed ovulation