The Dawn of
Man
Fossil Hominids
The Critters
Australopithecines
A. robustus
Sahelanthropus tchadensis
A. boisei
•Unveiled July 10, 2002
•Toros-Menalla locality, Djurab Desert, northern
Chad, central Africa
•Fauna includes aquatic and amphibious animals
alongside gallery forest and savanna fauna
A. garhi
A. aethiopicus
A. africanus
A. bahrelghazali
K. platyops
A. afarensis
A. anamensis
–Fish, crocodiles, primates, rodents, elephants, equids,
bovids
Ardipithecus
Ar. ram. kadabba
O. tugenensis
S. tchadensis
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6
5
4
3
2
Millions of Years Ago
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•Suggests hominid lived close to a lake, but not far
from a sandy desert
•Biochronology suggests an age between 6 and 7
million years
Sahelanthropus tchadensis
Sahelanthropus tchadensis
•Six specimens: nearly complete skull and several
fragmentary lower jaws
•Unique mosaic of primitive and derived characters
–Primitive: small cranial capacity (320-380 cc), large
central incisor, non-incisiform canines
–Derived: Reduced canines, thick molar enamel, nuchal
crest positioning suggesting bipedalism
•Skull nicknamed Toumaï
–Local name for a child born perilously close to the start
of the dry season (fossils occurred near the earliest
evidence of a central African desert)
•Some argue that it is a fossil gorilla!
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Orrorin tugenensis
•Lukeino Formation at Tugen Hills, Kenya
–Baringo region, near Kanapoi
•Dated at 6 m.y.a.
•Discoverers take great pains to show disimilarity
between Ororrin and the australopithecines, and
similarity between Orrorin and Homo
–The teeth are relatively small and retain thick enamel
–Femur does not rule out bipedalism, but is inconclusive
Orrorin
tugenensis
Earliest Hominids
LT 329: Lothagam
Photo by I.M. Campbell
•Dating is set at 5.8 –5.6 mya
•Jaw fragment shows numerous features
reflecting improved power and efficiency in
molar grinding
–Cannot be distinguished from later Pliocene
australopithecines including A. afarensis
(Kramer) and A. ramidus (White)
Ardipithecus ramidus kadabba
Toe
Toebone
bone
Ardipithecus ramidus kadabba
•Discovered at Aramis, Ethiopia
•Announced in July 2001
•Dated at 5.2 –5.8 million years
•Several jaw and bone fragments
–Toe bone resembles A. afarensis, suggesting
bipedality
Mandible
fragment
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Ardipithecus ramidus
Ardipithecus ramidus ramidus
•Discovered at Aramis, Ethiopia
•Announced in September 1994
•Dated at 4.4 million years
•Remains consist of skull and jaw fragments.
•Other fossils found with it indicate that it
may have been a forest dweller
New Controversy
Ardipithecus ramidus--2
•Teeth are intermediate between those of earlier
apes and A. afarensis, but one baby tooth is very
primitive, resembling a chimpanzee
–Thin enamel on the molars
•Undescribed remains suggest bipedalism
–Foramen magnum positioned forward
–Humerus does not appear to be weight bearing
–Limestone encased partial skeleton suggests bipedality
•For over a century we have expected fossils
to look more and more ape-like as we
approach the common ancestor with chimps
•Recently a number of the features that have
been assumed to be derived associated with
the face and teeth are being re-evaluated
–We
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kt
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ommon
ancestor looked more hominid than ape-like in
these features, making it more difficult to tell
when we have a very early hominid like
Sahelanthropus or Orrorin
Original Model
Modern
African
Apes
Modern
Man
6 - 8 million years
New Notions
Modern
African
Apes
6 - 8 million years
Common
Ancestor
Common
Ancestor
More ape-like
Modern
Man
More hominid-like
More ape-like
More hominid-like
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Australopithecus anamensis
Australopithecus anamensis
•Named in August 1995
•Material consists of 9 fossils from Kanapoi
in Kenya and 12 fossils from Allia Bay in
Kenya
•Aged between 4.2 and 3.9 million years ago
•Mixture of primitive features in the skull,
and advanced features in the body
Australopithecus anamensis--2
•Teeth are a mix of features
–Hominid thick enamel on molars
–Ape-like sectorial lower first premolar
–Relatively large canines
•Tibia suggests bipedality
•Humerus is extremely hominid in form
Australopithecus afarensis
Lucy: 40% complete skeleton
Sectorial
premolars
Australopithecus afarensis
•Aged between 3.9 and 3.0 million years ago
•Apelike face with a low forehead, a bony
ridge over the eyes, a flat nose, and no chin
•Cranial capacity from 375 to 500 cc
–Within chimp range, 1/4 - 1/3 modern humans
•Pelvis and leg bones far more closely
resemble those of modern man, and leave
no doubt that they were bipedal
Australopithecus afarensis
Guesstimate based on fragments
First nearly complete skull
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Australopithecus
afarensis, 4
•Laetoli footprints
•Discovered by Mary
Leakey
•Volcanic tuff dated at
almost 3.5 million
years
•Upright, bipedal
locomotion of two or
three hominids
Australopithecus afarensis, 5
•Canine teeth are much smaller than those of
modern apes, but larger and more pointed
than those of humans, and shape of the jaw
is between the rectangular shape of apes and
the parabolic shape of humans
•Females were substantially smaller than
males, a condition known as sexual
dimorphism
Australopithecus bahrelghazali
Australopithecus afarensis, 6
•Height varied between about 107 cm (3'6")
and 152 cm (5'0")
•Finger and toe bones are curved and
proportionally longer than in humans, but
the hands are similar to humans in most
other details
Australopithecus
bahrelghazali
•Age estimated at 3 - 3.5 mya due to faunal
similarity with Hadar
•Single mandibular fragment is generally
similar to Australopithecus afarensis
–Incisiform canines, bicuspid first premolar
•Differences from A. afarensis include:
–More verticle interior surface of the mandibular
symphysis
–Premolars have thin enamel and three roots
(afarensis usually has one or two roots)
Kenyapithecus platyops
•From the site of Lomekwi, western side of Lake Turkana
in northern Kenya, named in 2001
• More than 30 skull and dental fragments
– Two have been assigned to K. platyops
– Other fragments not yet assigned to any genus or species
Photograph by Michel Brunet
KT12/H1
• Found in deposits reliably dated to between 3.5 million and
3.2 million years ago
• Other mammalian species found at Lomekwi suggest that
the site was part of a complex mixture of grassland and
wooded habitats
– Like other roughly contemporary sites such as Laetoli (Tanzania)
and Hadar (Ethiopia), where remains of A. afarensis have been
found
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Kenyapithecus platyops
Lieberman on Kenyapithecus platyops
• The fossil resembles chimpanzees and A. anamensis in
having a small earhole
– It shares many other features of primitive hominins with A.
afarensis and A. anam ensis
•Cheek teeth with thick enamel
•A small brain the size of that of a chimpanzee
•Flat nasal margins
• It also has several important derived features
– An anterior origin for the root of the cheekbone arch on the upper
jaw
– The existence of a flat plane beneath the nose bone (and so the
appearance of a flat face)
– A tall cheek region
Holotype KNM-WT 40000 a, left lateral view (markers indicate the plane separating the distorted neurocranium and
the well-preserved f ace). b, Superior view. c, Anterior view. d, Occlusal view of palate. Paratype KNM-WT 38350. e,
Lateral view. KNM-WT 40001. f , Lateral view. g, Inf erior view. Scale bars: a–c, 3 cm; d–g, 1 cm. (Leakey et al. 2001)
• Postcanine teeth and brow of the skull are smaller than in
A. garhi
Kenyapithecus platyops
More Lieberman
vs. Homo rudolfensis
•KNM-WT 40000 has a small cranial
capacity but otherwise looks much like the
famous KNM-ER 1470 fossil, generally
referred to as Homo rudolfensis
–These similarities are mostly in the face, and
include the flat plane beneath the nose bone, the
tall, vertically oriented cheek region, and the
lack of a depression behind the ridge of the
brow.
KNM- WT 40000
Taung Child
KNM- ER 1470
Mrs. (?) Ples (Sts 5)
Australopithecus africanus
•A. africanus existed between 3 and 2
million years ago
•Similar to afarensis, bipedal, but slightly
larger body
•Cranial capacity ranging between 420 and
500 cc
•Molars are a little bigger than in afarensis
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Australopithecus africanus, 2
•The shape of the jaw is fully parabolic, like
humans
•The canine teeth, diastema in upper
dentition, and sectorial first lower premolars
are further reduced compared to A.
afarensis
Australopithecus
garhi
Photograph by David Brill
Australopithecus garhi
• From Bouri, Middle Awash, Ethiopia, 2.5 m.y.a.
• Large teeth
– Cheek teeth at or beyond the robust australopithecine extremes
– Large anterior teeth
•Bigger than those of the largest australopithecines
•Based on tooth size A. garhi fits with schemes that see gracile
australopithecines as a direct human descendents
–Canine-to-premolar/molar size ratios are comparable between A.
garhi, the gracile australopithecines and early Homo
• Long forelimbs and long hindlimbs
• Researchers argue that A. garhi represents a direct ancestor
of modern humans that is derived from africanus which is
likely derived itself from afarensis
Australopithecus aethiopicus
•Lived between 2.6 and 2.3 million years ago
–Known from one major specimen, the Black
Skull, and a lower jaw from Omo
Skull
–May be an ancestor of robustus and boisei, but
it has a baffling mixture of primitive and
advanced traits
•Brain size is small, at 410 cc
Australopithecus aethiopicus
Australopithecus
aethiopicus
Photograph by David Brill
Photograph by Robert I.M. Campbell
Photograph by Robert I.M. Campbell
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Australopithecus aethiopicus
Australopithecus aethiopicus
•Parts of the skull, particularly the hind
portions, are very primitive, most
resembling A. afarensis
•The massive face, jaws, and single tooth
found, and the largest sagittal crest (the
bony ridge on top of the skull to which
chewing muscles attach) in any known
hominid, are more reminiscent of A. boisei
Photograph by Robert I.M. Campbell
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