Chapter 10
Hominid Origins in Africa
Chapter Outline
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Early Primate Evolution
Miocene Fossil Hominoids
The Bipedal Adaptation
Early Hominids from Africa (PreAustralopithecus Finds)
Australopithecus from East Africa
Chapter Outline
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Early Homo
South African Sites
Interpretations: What Does It All Mean?
Adaptive Patterns of Early African
Hominids
Early Primate Evolution
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Earliest fossils identifiable as hominids
are from Africa.
From new discoveries, the earliest
hominids are now thought to date as far
back as the end of the Miocene (7–5
m.y.a.).
These discoveries have all been made
very in the last five years.
Eocene primates
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There are more than 200 species of Eocene
primates found in North America and Europe.
 Some are probably ancestors of the
prosimians, and others are probably related
to the tarsier.
 New discoveries of late Eocene primates from
North Africa, the Persian Gulf, and China,
indicate anthropoid origins were well
established by this time.
Oligocene (34-23 m.y.a.)
Anthropoid Remains
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Most come from the Fayum, in Egypt.
The Fayum anthropoids include the
genera Apidium and Aegyptopithecus.
– Apidium was a squirrel-sized arboreal
quadruped.
– Aegyptopithecus is about the size of a
howler monkey. It has a small brain and a
long snout, and has no hominoid or Old
World monkey derived features.
Location of the Fayum,
Oligocene Site in Egypt
Inferred Paleobiological
Aspects of Oligocene Primate
Apidium
750–1,600 g
Weight Range
(2–3 lb)
Aegyptopithecus
6,700 g
(15 lb)
Substratum
Arboreal
Arboreal
Locomotion
Quadruped
Quadruped
Fruit, seeds
Fruit, some
leaves?
Diet
Major Events in
Early Primate Evolution
Miocene Fossil Hominoids
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Continental drift during the Miocene altered
climatic patterns and created new migration
routes.
 The initial Miocene was warmer than the
preceding Oligocene.
 The Arabian Plate “docked” with northeast
Africa around 16 m.y.a., allowing African
animals direct passage into southwest Asia.
Miocene Hominoid
Distribution, From Fossils
Discovered
Miocene Hominoids
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May be grouped geographically into African,
European, and Asian forms.
– The African forms (23-14 m.y.a) include the bestknown genus Proconsul from Kenya.
– The European forms (16-11 m.y.a.) include a
number of derived forms that are not well
understood.
– The Asian forms (16-7 m.y.a.) are the largest and
most varied group. The best-known genus is
Sivapithecus.
Miocene Hominoids: 5
Generalizations
1.
2.
3.
4.
5.
They are definitely hominoids.
They are mostly large-bodied hominoids.
Most are derived relative to living apes.
Sivapithecus from Turkey and Pakistan has
facial features similar to living orangutans.
There are no fully documented, definite
hominids among the Miocene material,
although it now appears that hominids
diverged in the latter Miocene.
Hominid Bipedalism
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The pelvis is shaped
more in the form of
a basin to support
internal organs;
moreover, the ossa
coxae are shorter
and broader, thus
stabilizing weight
transmission.
Hominid Bipedalism
The foramen magnum is
farther underneath the
skull, so the head is
more or less balanced
on the spine and
requires less robust
neck muscles to hold
the head upright.
Hominid Bipedalism
The spine has two
distinctive curves—a
backward (thoracic)
one and a forward
(lumbar) one—that
keep the trunk (and
weight) centered
above the pelvis.
Hominid Bipedalism
Lower limbs are
elongated, as shown by
the proportional lengths
of various body
segments (e.g., in
humans the thigh
comprises 20% of body
height, while in gorillas
it comprises only 11%.
Hominid Bipedalism
The femur is angled
inward, keeping
keeping the legs
more directly under
the body; modified
knee anatomy also
permits full
extension of this
joint.
Hominid Bipedalism
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The big toe is enlarged
and brought in line with
the other toes; in
addition, a distinctive
longitudinal arch forms,
helping absorb shock
and adding propulsive
spring.
Earliest Hominids
– All are from Africa.
– The earliest traces of hominid evolution
were thought to date to between 3 and 4
million years ago in 1999, but the earliest
traces may date to 7 million years ago.
– A nearly complete cranium from TorosMenalla, Central Africa, was discovered in
2001 and has been assigned the name
Sahelanthropus tchadensis.
Sahelanthropus tchadensis
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The braincase is small but it has huge
browridges combined with a sagittal crest
and large muscle attachments in the rear.
The face does not protrude, unlike other
early hominids.
There are no postcranial elements, so its
locomotor capabilities are unknown.
The hominid status of Sahelanthropus is
insecure, and some have argued it is
actually an ape.
Discoveries from East Africa
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The Tugen Hills area is located near Lake
Baringo, Kenya.
– The fossils found here have been named Orrorin
tugenensis and date to about 6 m.y.a.
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Fragmentary, late Miocene (5.8-5.2 m.y.a.)
fossils discovered in 1997 through 2001 in
the Middle Awash (Ethiopia) .
– Remains consist of mostly teeth, a jaw fragment,
and some pieces of the limbs (these have been
assigned to Ardipithecus kadabba).
Ardipithecus from Aramis
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Fossil remains of perhaps 50 individuals from
Aramis (Ethiopia) were excavated between
1992 and 1995 and date to about 4.4 m.y.a.
 The remains provide anatomical evidence of
bipedalism, the criterion for hominid status.
 The team of excavators have suggested that
the Aramis hominids be assigned to a new
genus and species, Ardipithecus ramidus.
Australopithecus from East
Africa
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East African fossil remains assigned to the
genus Australopithecus date from 4.2 to 1.4
m.y.a.
 The earliest Australopithecus remains come
from Allia Bay and Kanapoi (4.2-3.9 m.y.a.).
 The limb remains indicate bipedalis, and the
molars have thick enamel caps.
 They retain primitive characteristics such as
large canines and a sectorial lower first
premolar.
Laetoli
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Dated at between 3.5 and 3.7 m.y.a.
Fossilized hominid footprints were found
in an ancient volcanic bed.
Despite agreement that these
individuals were bipedal, some
researchers feel they were not bipedal
in the same way as modern humans.
Hadar (Afar Triangle)
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Dating calibrations suggest a range of dates
from 3.9 and 2.3 m.y.a.
– "Lucy" an Australopithecus afarensis female, was
recovered here.
– Group of bones representing 13 individuals and
including 4 infants, suggest a social unit died at
the same time..
– Some stone tools may be 2.5 million years old,
making them the oldest cultural evidence yet
found.
Bouri (Middle Awash)
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Several fossils were discovered dating to 2.5
m.y.a.
 These fossils are quite different from other
Plio-Pleistocene hominids:
– Projecting face
– Very large back teeth
– Long hind limbs
 Animal bones found with these fossils show
clear signs of butchering.
Australopithecines from
Olduvai and Lake Turkana
– Represent two different genera and up to
six different species, later in time and more
derived than A. afarensis.
– The virtually complete cranium of the 2.5
m.y. old WT 17000 (Australopithecus
aethiopicus) from West Lake Turkana is the
earliest trace of the “robust” forms in East
Africa.
Olduvai Gorge
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Louis and Mary Leakey conducted
continuous excavations from the 1930's
to early 1980.
Paleontological evidence includes more
than 150 species of extinct animals
which can provide clues to the
ecological conditions of early hominid
habitats.
South African Sites
The first australopithecine “the missing link”
between apes and humans was discovered at
a quarry at Tuang.
 As the number of discoveries accumulated, it
became clear that the australopithecines
were not simply aberrant apes.
 The acceptance of the australopithecines as
hominids required revision of human
evolutionary theory.
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“Robust” Australopithecines
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Similar to those found in East Africa.
 Small cranial capacities, large broad faces,
and very large molars and premolars.
 Most researchers agree these hominids have
distinctive enough dental proportions and
facial architecture to be designated a
separate species (A. robustus).
 All “robust” species are adapted to a diet of
hard food items such as seeds and nuts.
“Gracile” Australopithecines
The “robust” lineage is present in both east
and South Africa, but the “gracile” lineage (A.
africanus) is only in South Africa.
 “Gracile” australopithecines are small-brained
but not as large-toothed as the “robust”
varieties.
 There seem to be no significant differences in
body size between the “robust” and “gracile”
varieties.
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Geology and Dating Problems
in South Africa
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The South African hominid sites have
complex geologic contexts.
 Hominid remains are found in limestone cliffs,
caves, fissures, and sinkholes mixed with
other fossils in blocks of sand and stone.
 The dating of the South African sites has
been difficult, especially since there are no
volcanic deposits.
Plio-Pleistocene Hominids:
Ongoing Taxonomic Issues
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Determining hominid status of
Sahelanthropus, Ardipithecus, and Orrorin
specimens.
 Determining whether specimens assigned to
A. anamensis and A. garhi should remain
distinct from A. afarensis at the species level.
 Determining the number of genera present.
 Determining the number of species present in
the material assigned to early genus Homo.
Groups of
Plio-Pleistocene Hominids
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Specimens recovered represent close to 200
individuals from South Africa and more than
300 from east Africa.
 The specimens have been divided into four
broad groupings:
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Set I Basal Hominids.
Set II Early Primitive Australopithecus.
Set III Later, more derived Australopithecus.
Set IV Early homo.
Estimated Body Weights and Stature in
Plio-Pleistocene Hominids
A. afarensis
Body Weight
Male
Female
99 lb
64 lb
Stature
Male Female
59 in.
41 in.
A. Africanus
90 lb
65 lb
54 in.
45 in.
South African
“robust”
88 lb
70 lb
52 in.
43 in.
East African
“robust”
H. Habilis
108 lb
75 lb
54 in.
49 in.
114 lb
70 lb
62 in.
49 in.