Chapter 7
 Charles
Dawson found a fossil that he said was the
“missing link”
 It had a human skull and an ape jaw
 Called Piltdown Man
 It was a hoax (human skull fused with an
orangutan jaw)
 Shows people (wrongly) thought human ancestors
were hybrid ape-men
 It
is not big brains
 It is bipedalism
 We began walking bipedally 7 mya (million
years ago)
 We got big brains only 2 mya
 Please
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remember:
Hominids are ancestors of any apes
Hominins are ancestors of humans
 Historically,
scientists believed the identifiable
feature of human ancestors was big brains
 This was not supported in the fossil record
 How would we tell bipedalism from a fossil?
 Also
remember that humans go in the ape
classification of Hominoid
 Why?
 Also
remember that humans go in the ape
classification of Hominoid
 Why?
 Y-5 molar
 No tail
 Shared DNA
 1.
foramen magnum underneath skull
 2. short, wide pelvis
 3. long legs
 4. no opposable big toe
 5. double-curved spine
 Honing
canine: apes’ canines cut and shred food
and are large and dangerous and they have a
diastema.
 Humans have small, nonhoning canines and no
diastema
 Apes have powerful chewing muscles and a
sagittal crest for extra power. Humans are weak
chewers
 Why? What invention did human ancestors have
that made food processing easier?
 It
is hypothesized that our ancestors were
knuckle-walkers, which allowed for easier
upright standing
 Climate and environmental changes may
have selected for bipedalism
 Darwin’s
Hunting Hypothesis: because of
similarities between humans and apes, he
concluded Africa must be our origin. There
must have been something to shift us to
walking on the ground
 Unique human traits:
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Bipedal vs quadrupedal
Tiny canines vs large canines
Tool use vs no tool use
Big brains vs smaller brains
 Darwin’s
Hunting Hypothesis: Darwin asked
what advantages bipedalism had and he
concluded it freed the hands for holding
weapons
 We now know that we walked many millions
of years before tools were made, but his
hypothesis laid the foundation
 Another
hypothesis involved the forest
becoming fragmented, and hominids walking
on two legs in between patches of trees.
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Used less energy
Could see predators
Could hold things with hands
Less of the body in direct sunlight
 Owen
Lovejoy’s Provisioning Hypothesis:
heavy parental investment by mothers led to
bipedalism
 Males would better provision females if
bipedal (free hands to carry more food)
 Better infant survival and higher fitness for
mother
 Small level of sexual dimorphism in fossils
supports this (cooperation of male and
female pair…not males fighting for one
female)
 Pros:
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Can carry things (frees hands)
Can see predators
Can save energy
 Cons:
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We are slow
If carrying items, makes us easy targets
Back injuries
If injure a foot, very difficult to get around
 Pre-Australopithecines
 Australopithecines
 Paranthropus
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Rift Valley
Volcanic rock
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What dating technique?
 Sahelanthropus
tchadensis: earliest
ancestor/oldest biped
 “Chad Man”
 7-6 mya
 Central Africa (Chad)
 Small brain (350 cubic cm, cc)
 Bipedal (foramen magnum)
 Nonhoning canine
 Close to the divergence of human line from
ape line
 Sahelanthropus
tchadensis
 Orrorin
tugenensis:
 “Original Man”
 6 mya
 Mostly femurs (thigh bone)
 Show bipedalism
 Nonhoning canines
 Aridpithecus
ramidus:
 “Great-grandma”
 “Ardi”
 4-6 mya
 Bipedal
 All species so far still spent time in the
trees…why?
 May be direct ancestor to Australopithecines
 Aridpithecus
ramidus:
 Australopithecines:
 Hundreds
of fossils from at least 7 species
 Not 100% sure of all the relationships
 Australopithecus
africanus:
 Raymond Dart found a small skull in a cave
 “Taung Baby”
 4-3 mya
 Thought baby ape at 1st
 Small teeth, bidpedal foramen magnum
 Later adult fossils had small canines too
 *Showed that bipedalism came way before
big brains*
 Australopithecus
africanus:
 Australopithecus
afarensis:
 Kenya and ethiopia
 3 mya
 Best-known and best-represented
 “Lucy” over 40% of skeleton (but over 80%
because skeleton is symmetrical)
 If Ardi is great-grandma, Lucy is grandma
 Foramen magnum, pelvis, legs, and feet all
bipedal
 Curved fingers (why?)
 Small brain still (430 cc)
 Australopithecus
 Smaller
afarensis:
canines
 Laetoli Prints: fossilized footprints in
volcanic ash (how would you date these??)
 Showed bipedalism and ‘first family’ (2
adults, 1 child)
 Australopithecus
afarensis:
 Australopithecus:
 Beginning
3mya, two lines of hominin
evolution occurred, each with unique
adaptations
 One line went extinct and one line led to
genus Homo
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This next group is the second line that went extinct
Some still call this group “robust” Australopithecus
but there are enough differences that I split them
into a new genus Paranthropus
Paranthropus:
2.5 mya
Larger, more robust bodies but small brains
Sagittal crest
Huge molars for crushing tough food
Flaring face
Do we have these adaptations?
Specialized food source may have led to extinction
 Paranthropus:
AUSTRALOPITHECUS
 Biped
 Slender
 Small
brain
 Rounder head
 Smaller teeth
 Varied diet
PARANTHROPUS
 Biped
 Robust
 Small
brain (smaller
than A.)
 Flared head
 Sagittal crest
 Large molars
 Specializeed, tough
diet