Transcript Australopithecus aethiopicus

Australopithecus africanus
Discovered: 1924 in Taung limestone
quarry in South Africa by Raymond Dart
 Age range: 3.0 – 2.2 mya
 Type specimen: Taung Child (6 yo)
 Cranial capacity: 440 cc (avg.)
 Features: slightly projecting lower face,
large molars, small front teeth &
canines, short face
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Australopithecus africanus
Australopithecus robustus
Discovered: 1936 by Robert Broom in
South Africa
 Age range: 1.8 -1 mya
 Cranial capacity: 530 cc
 Features: robust features = sagittal crest,
large teeth, thick & wide cheekbones,
large face, large jaw, small brain
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Diet of hard food items: nuts, seeds, tubers,
roots, leaves
Australopithecus boisei
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Discovered: 1959 by Mary Leakey in Tanzania
(East Africa)
Note: Originally named “Zinjanthropus boisei”
Age range: 2.2 – 1.3 mya
Cranial capacity: 530 cc
Features: “Hyper-robust” – massive jaw, huge
molars & big teeth w/wear, prominent sagittal
crest
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Cranial-dental features work as “grinding machine”;
nicknamed “Nutcracker Man”; ate seeds, nuts, roots,
tubers, leaves (NOT a tool maker---teeth are tools)
Australopithecus afarensis (aka “Lucy”)
Discovered: 1974 in Hadar, East Africa by
Don Johanson
 Age range: 3.9 – 3 mya
 Significance:
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Antiquity - 1 my older than any
other hominid found at that time
 40% complete – nearly all bones
represented
 Established bipedalism in earliest
known hominid (w/small brain)
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Lucy’s Features
Only found in E. Africa
 Cranial capacity – 375 – 550 cc.
 Ape-like face
 Low forehead
 Bony ridge over eyes
 Flat nose
 No chin
 Protruding jaws
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Lucy’s Features, Cont.
Large, thickly enameled back teeth
 Slightly projecting upper canine
 U-shaped jaw (like apes, but not identical)
 3 ½ - 5 ft. tall
 Arms longer than legs
 Pelvis & leg bones adapted for bipedalism
 Curved finger & toe bones
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“The First Family” – A. afarensis
Discovered: 1975 by Don Johanson
 Features: Remains of 13 individuals
(male, female, adults, juveniles)
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Highly sexually dimorphic (males much bigger
than females)
Same features as Lucy
Significance: strong evidence of variation
within the species & for A. afarensis as a
hominid
A. afarensis, cont.
The Laetoli Footprints
 Discovered: 1978 in Tanzania by Mary
Leakey
 Age: 3.7 – 3.5 mya
 Features: Prints reveal human-like stride;
big toe in line with others; arch in foot
 Significance: Establishes bipedality in
earliest hominids
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Evolution of Bipedalism
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Anatomical Adaptations
Australopithecines have
wide, short pelvis
Femur is angled inward
toward the knees to bear
upper body weight
Modern human pelvis is
rounded
Early Hominid Bipedalism
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Not EXACTLY like modern humans
A. afarensis ankle & shoulder joints more like a
chimp’s (more flexibility)
A. afarensis finger and toe bones retain some
curvature
Foramen magnum indicates A. afarensis is an
obligate biped (committed to bipedalism)
Conclusion: A. afarensis spent time in trees & on
the ground
Comparison of Hominid Skeletons
Adaptive Patterns of the
Australopithecines
Bipedal
 Small bodied (avg. height of 4-5 ft.)
 Small brains (approx. same as modern
chimp)
 Tool use similar to modern chimps
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NOT stone tool user
Small, social groups of bonded
males/females & offspring
The Australopithecines, Continued
Lived in mixed woodland/savannah
 Foragers – gathered nuts, seeds, fruits,
roots, tubers
 Small populations
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Genetic drift, mutations, selective pressures =
rapid genetic divergence & eventual speciation
Represent a successful lifestyle
Adaptive Patterns of Early African
Hominids
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Gracile australopiths
More omnivorous
More arboreal
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Reflected in foot, ankle,
hand, wrist bones
A. afarensis, A. africanus
Adaptive Patterns of Early African
Hominids
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Robust
australopiths
Diet of hard food
items
Less arboreal
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Due to food sources
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Extinct 1 mya
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A. robustus, A. boisei
Different Genus? Paranthropus
The Pre-Australopithecines
Ardipithecus ramidus
Discovered: 1994 in Ethiopia by various
research teams
 Age range: 5.8- 4.4 mya
 Features: most complete ancient hominid
skeleton – bones of hand, feet, limbs,
pelvis, most of skull & teeth; remains of
males, females, juveniles
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A. ramidus, cont.
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Mix of ape & human traits:
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Small canines
Grasping big toe (only biped w/ this feature)
Long arms, short legs
Small brain
Hand bones NOT adapted for knuckle-walking
Small molars
Diet: omnivorious - plants, fruits, insects, nuts,
seeds
Environment: lush woodlands, forests
Ardipithecus ramidus
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Significance:
 1 my older than Lucy
 Closest established hominid to Last Common
Ancestor with chimps
 Evidence of bipedalism arising in a more
arboreal context than previously thought
Ardipithecus ramidus,
cont.
Lucy (Au. afarensis) at left
Ardi (Ard. ramidus) on right
Ardipithecus ramidus
Orrorin tugenensis aka “Millenium Man”
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Discovered: 2001 in western Kenya
Age range: 6 mya
Remains: Fragmentary arm & thigh bones; lower
jaws & teeth
Features: Limb bones larger than later hominid
species
Cranial capacity: Not yet determined
Notes: Some evidence of bipedality & tree
climbing; dental & some skeletal features more
human than ape like
Significance: More evidence that bipedalism may
have originated in the trees
Pre-Australopithecines, cont.
Sahelanthropus tchadensis
 Found in central Africa, country of Chad
 Nearly complete cranium
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Small braincase: 370-380 cc
Massively built, heavy browridges, crest in
back, large muscle attachments
Reduced upper canine
Small, vertical face
Cannot determine bipedality
 OLDEST possible hominid
 Common ancestor?
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Other Australopithecines
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You will not be tested on any of the
following species, they are included here
only to demonstrate the VARIATION
present in early hominid evolution
Australopithecus aethiopicus
Discovered: 1985 in Kenya
 Age range: 2.8 – 2.2 mya
 Cranial capacity: 410 cc
 Features: Very broad projecting face
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Large sagittal crest
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Massive jaws and molars
 Notes: Ancestor to A. boisei and A.
robustus
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Australopithecus anamensis
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Discovered: 1995 in Kenya by Meave Leakey
Age range: 4.2 – 3.9 mya
Remains: Skull, teeth, leg and arm bones
Cranial capacity: Not yet determined
Features: Thickly enameled teeth
Notes: Skull features are primitive
Body features are humanlike*
*Skull and skeletal bones may not be from the
same species
Australopithecus garhi
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Discovered: 1999 in Ethiopia
Age range: 2.5 mya
Remains: 5 hominids; 1 partial skull, parts of
limb skeleton
Cranial capacity: Not yet determined
Features: Extremely large back teeth, large front
teeth, projecting face
Notes: Long forelimbs and long hindlimbs
Found in assoc. w/butchered animal
bones
Could A. garhi be first stone tool user?
Kenyanthropus platyops
Discovered: 2001 in Kenya by R. Leakey
 Age range: 3.5 mya
 Remains: Partial skull
 Cranial capacity: 410 – 440 cc
 Features: Large, flat face; small teeth
 Notes: Some features foreshadow Homo
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