The Dawn of
Man
Fossil Hominids
The Critters
Australopithecines
Sahelanthropus tchadensis
A. robustus
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
Ardipithecus
– Fish, crocodiles, primates, rodents, elephants, equids,
bovids
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)
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Orrorin tugenensis
• Lukeino Formation at Tugen Hills, Kenya
• 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
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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
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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
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
New Controversy
• 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’re beginning to think that the common
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. anamensis
• 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 face). 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, Inferior 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
– 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
Australopithecus robustus
Australopithecus robustus
• Body similar to A. africanus, but larger and
more robust skull, jaws, and teeth
• Found primarily in cave deposits estimated at
1½ - 2 mya from Swartkrans and Kromdraai in
South Africa
• Massive face is flat or dished, with no forehead
and large brow ridges
• Relatively small front teeth, but massive
grinding teeth (molars and premolars) in a large
lower jaw
Australopithecus robustus, 3
• Most specimens have sagittal crests
• Diet would have been mostly coarse, tough
food that needed a lot of chewing
• Average brain size is about 530 cc
• Animala bones excavated with A. robustus
skeletons suggest to some workers that the
australopithecines may have used bones as
digging tools
Australopithecus boisei
• A. boisei existed between 2.1 and 1.1
million years ago
• Similar to A. robustus, but the face and
cheek teeth even more massive
• Cranial capacity averages about 530 cc
• Some experts consider A. boisei and A.
robustus to be variants of the same species
– Others place them in a separate genus,
Paranthropus
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KNM-ER 406
Gracile vs. Robust
• Australopithecus afarensis and A. africanus
are known as gracile australopithecines,
because of their relatively lighter build,
especially in the face and teeth
– Gracile means slender, and in paleontology is
used as an antonym to robust
– Despite this, A. afarensis and A. africanus were
still more dentally robust than modern humans
Photograph by David Brill
Gracile vs. Robust, 2
• Australopithecus aethiopicus, A. robustus
and A. boisei are known as robust
australopithecines, because their skulls are
more heavily built
Discovery of this jaw in
1960 led Louis Leakey
to name a new species,
Homo habilis, as direct
ancestor of man, with
Homo erectus
representing an extinct
side branch
OH 7
– The jaws, cheek teeth, and face are the most
heavily built aspects of these fossil hominids
– The canine teeth are quite small in all of these
species
Photograph by John Reader
Homo habilis
• Fossils named “handy man” because of the
suggestion of evidence of tools found in
contemporary deposits
• Lived between about 2.4 and 1.5 million
years ago
• Similar to australopithecines in many ways
• Face is primitive, but projects less than in A.
africanus
Photograph by John Reader
KNM-ER 1813
Photograph by David Brill
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Homo habilis, 2
• Back teeth are smaller than those of the
australopithecines, but still considerably
larger than modern humans
• Average cranial capacity, at 650 cc, is larger
than in australopithecines
– Brain size varies between 500 and 800 cc,
overlapping the australopithecines at the low
end and H. erectus at the high end
Homo habilis, 4
Homo habilis, 3
• Brain shape is more humanlike
– Bulge of Broca's area, essential for speech, is
visible in one H. habilis brain cast, indicating it
may have been capable of rudimentary speech
• H. habilis was about 127 cm (5'0") tall, and
about 45 kg (100 lb) in weight, although
females may have been smaller
KNM-ER 1470
Homo rudolfensis
• Habilis has been a controversial species
– Some scientists have not accepted it, believing
that all H. habilis specimens should be assigned
to either the australopithecines or Homo erectus
– Many now believe that Homo habilis combines
specimens from two or three different species
• Homo habilis
• Homo rudolfensis
• Homo ergaster
Photographs by David Brill
Homo rudolfensis
• The species designation of Homo rudolfensis is much
debated
KNM-ER 992
Homo ergaster
– Is it a separate species
– Is it an australopithecine rather than a homonine
• One of the main problems with H. rudolfensis species is that
there are no postcranial remains
– Large brains in conjunction with megadont postcanines
– Some researchers see the larger brain and tooth size as indicative
of allometric changes due to increased body size--rudolfensis and
habilis are the same, with the former the males and the later the
females
– Some see rudolfensis as the ancestor of habilis with a decrease in
brain size occurring
– Others see the two on completely different evolutionary lines
Photograph by Robert I.M. Campbell
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Homo ergaster
KNM-WT 15000
• Homo ergaster is one of the more problematic of
species designations
• Each researcher that sees ergaster as valid sees
different specimens as belonging or not belonging
• Most researchers see too little difference between
ergaster and erectus to form the basis of a species
• As a general rule of thumb, one can consider most
attributed ergaster specimens to be early erectus
geographically confined to Africa
Photographs by David Brill
Homo erectus
from Zhoukoudian
Weidenreich
Tattersall and Sawyer
Homo erectus
• Wolpoff claims that H. erectus is an invalid taxon,
though few accept this interpretation at this point
in time
• Others believe the material attributed to erectus
should be split into several different taxons
– Asian and later African material remaining as H.
erectus--not contributing to modern humans
– Early African material as H. ergaster
– European material as H. heidelbergensis
Photographs by David Brill
KNM-ER 3733
Homo erectus
• An increase in brain size to approximately 900 cc
• Reduction in postcanine dentition and a decrease
in jaw size
• Vertical shortening of the face.
• Shortening arm bones, especially forearms to very
modern limb proportions
– Postcranial proportions are very similar to tropically
adapted modern humans
Photographs by David Brill
• Development of a more barrel-shaped chest
• The formation of an external nose
• Modern human size in terms of height
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Homo antecessor
• Approximate brain size of 1000 cc
• Marked double-arched browridge
Gran Dolina Material
Homo antecessor
– like later Neanderthals and Chinese H. erectus
• Canine fossa but no expanded maxilla
– May be due to the individual's young age since others (ATD 658) have an expanded maxilla
• Sharp nasal margin
• Shallow maxillary notch
• Reduced mandibular corpus thickness when compared to
H. ergaster or early H. erectus
• Small postcanines that resemble those of the habilines
• M3 reduced relative to M1
• Moderate taurodontism
– Characteristic of H. erectus and H. heidelbergensis)
• Large I2 dimensions that resemble H. heidelbergensis
Homo antecessor
Photograph by Javier Trueba
Homo heidelbergensis
from Arago
• An important feature that was discovered when the remains
were examined were cut marks that were present on most
of the material
– 12 parallel cut marks on a temporal fragment where the
sternocleidomastoid muscle attaches
– Cut marks on two foot phalanges where the flexor muscle lies
• Dismemberment was the likely goal
• Faunal material shows the same cut marks as the hominid
remains
– Very few carnivore tooth marks indicates that hominids were
mainly responsible for processing the bones
• This is the earliest well-documented case of cannibalism in
a hominid population, and this information is important for
deciphering the behavior of early hominids
Photographs by David Brill
Homo heidlebergensis
• An increase in brain size to approximately 1200cc
• A shift in the widest part of the brain case from
the cranial base to the parietal regions
• The rear of the cranial vault becomes more
vertical
• A gradual reduction in cranial robusticity
• A decline in postcranial robusticity
• A tendency for a shift from shorter more robust
stature to taller, leaner bodies
Mauer 1
Homo heidlebergensis
• 1907 Mauer sand pits in Germany
• Validated Schoetensack's
conviction that Pleistocene human
remains would be found in the
quarry
– Associated with rhino, bear, elephant,
bison, deer, and horse
• Schoetensack (1908) named a new
species of hominid, Homo
heidelbergensis
– New species not justified by
describing unique anatomical
features of the species
– Lack of older or other specimens kept
heidelbergensis from being accepted
Photograph by John Reader
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Homo heidelbergensis
Homo neanderthalensis
Neanderthal 1
Photograph by Rheinisches Landesmuseum Bonn
Homo neanderthalensis
Homo neanderthalensis
Mount Circeo
La Chapelle-aux-Saints
Photographs by John Reader
Photograph by Ministry of Culture, Italy
Inner Ear Morphology
Homo neanderthalensis
• An occipital bun
• A suprainiac fossa
• Position of the mastoid crest located behind the
external auditory meatus
• Position of the juxtamastoid crest located behind
the mastoid crest, and often larger than the
mastoid process
• Position of the mastoid process
• The supraorbital torus
• The supratoral sulcus
• A receding frontal
• Presence of lambdoidal flattening
Drawings by C. David Kreger
•
•
•
Another trait that is being looked at currently as a way of
distinguishing Neanderthals in the inner ear morphology
Researchers are trying to determine if the Neanderthals had a
unique inner ear morphology that can be used
When comparing the values of S/I, humans generally have a
value close to 1, chimpanzees have values greater than 1, and
Neanderthals have values less than 1
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References
• LEAKEY, MEAVE G., FRED SPOOR,
FRANK H. BROWN, PATRICK N. GATHOGO,
CHRISTOPHER KIARIE, LOUISE N. LEAKEY &
IAN MCDOUGALL (2001) New hominin genus from
eastern Africa shows diverse middle Pliocene lineages.
Nature 410, 433 – 440.
• LIEBERMAN, DANIEL E. (2001) Another face in our
family tree Nature 410, 419 – 420.
• Kreger, C. David (2001) A look at modern human origins.
http://www.modernhumanorigins.com/
Possible evolutionary
relationships of the hominids
• The five major genera,
with Kenyanthropus in
red, Homo in blue,
Paranthropus in green,
Australopithecus in black
and Ardipithecus in
yellow
– Question marks indicate
hypothetical or conjectural
relationships; horizontal
bars indicate uncertainty in
the species' temporal spans
• Lieberman, 2001
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