GENERAL SCOPE AND USES OF

PHYSICAL/BIOLOGICAL ANTHROPOLOGY

Course name: Physical Anthropology

Paper No. & Title: B.A./B.Sc. Anthropology 2nd semester

Paper –II

Topic No. & Title: 14/15 Australopithecines

(Australopithecus africanus)
Objective:
Most of all the Hominid fossils of Africa comparing with the
African apes have large brain, relatively reduced chewing or
molar teeth and limb bones that are, except in points of
details, like those of modern Homo sapiens. However, there
are at least four and perhaps five species of hominid that
lack expanded brain, the reduced molar teeth and the
skeletal features of Homo. They antedate or overlap with
earliest representatives of Homo and are known collectively
as the Australopithecines. Hence, this module aims to
understand importance of this hominid fossil
(Australopithecines) in tracing the evolutionary line of
present day human being.

Content & Script of the Programme

Introduction:
Most of all the Hominid fossils of Africa comparing
with the African apes have large brain, relatively reduced
chewing or molar teeth and limb bones that are, except in
points of details, like those of modern Homo sapiens.
However, there are at least four and perhaps five species of
hominid that lack expanded brain, the reduced molar teeth
and the skeletal features of Homo. They antedate or overlap
with earliest representatives of Homo and are known
collectively as the Australopithecines. Raymond Dart first
discovered in 1924 at Taung in South Africa. The finding
includes part of mandible, facial skeleton and endocranial
parts of a child. Dart named the skull as Australopithecus
africanus. The meaning of austral is south and pithecus
means ape. At first discoverer of the various
Australopithecine fossils named four to five genera, but now
the consensus of scientific opinion recognizes one genus
Australopithecus and two species, a slenderly built and
smaller form, Australopithecus africanus (Gracile form) and
larger roughly built Australopithecus robustus originally
called Paranthropus. The following are the fossils along with
the sites found in South Africa and East Africa:

Fossils of South Africa:

Place Fossils Discoverer

Taung Australopithecus africanus Raymond Dart, 1925

Kromdraai Paranthropus robustus Robert Broom, 1938

Makapansgat Australopithecus promethecus Robert Broom, 1948

Stenfontein Plesianthropus transvalensis Robert Broom, 1936

Swartkrans Paranthropus crassidens Robert Broom, 1947

 In South Africa, the gracile form occurs at three sites; they
are Taung, Makapansgat and Stenfontein, and Robust form at two
sites. They are, Kromdraai and Swartkrans.

Fossils from East Africa:

Ethiopia

Hadar: Australopithecus afarensis (Lucy) C. Johanson, 1974.

Omo: Australopithecus africanus, Australopithecus boisei,

Homo habilis and Homo erectus.

Kenya

Koobifora: Australopithecus boisei, Homo erectus.

Lothagam: Australopithecus africanus.

Lake Turkana: Australopithecus boisei, Homo habilis and

Homo erectus.
Tanzania

Olduvai Gorge: Zinjanthropus boisei (Australopithecus

boisei, II bed) 1959.

Homo habilis, Homo erectus.

by Leakeys (L.S.B. Leakey) in 1964.

Laetoli: Australopithecus africanus.

In East Africa, Louis Leakey made the first discovery

of a hominid fossil from Bed I of Olduvai Gorge in 1959. The
first discovery named Zinjanthropus boisei, now known as
Australopithecus boisei is considered to be a super robust
Australopithecus. Another important discovery was
announced in 1964 from Olduvai Gorge and named Homo
habilis.

Other important sites in East Africa are the Omo river

valley of Southern Ethiopia where both robust and gracile
forms have been found. Similarly both robust and gracile
forms were discovered from Hadar in Eastern Ethiopia and
Turkana region of Northern Kenya. Turkana region have
been studied by Richard Leakey since 1969 and over 120
hominid fossils have been discovered so far.
Classification:
i) Classification given by Loring Brace
Hominidae
______________________________Genus
Australopithecus Homo
__________________ ____________
A. africanus A. robustus Homo erectus Homo sapiens.
(A. afa; H. habilis)

ii) Classification given by John Robinson

Hominidae

_______________

Australopithecus Homo

_____________ ___________________

A. africanus A. robustus H. habilis H. erectus H. sapiens

(A. afa)

According to Loring Brace Homo habilis is the member of

Australopithecus africanus but for John Robinson it is not.
iii) Classification given by Donald C. Johanson

Hominidae

_____________________

Australopithecus Homo

__________________________
A. africanus A. afarensis A. robustus

T. Robinson’s Dietary hypothesis:

Going by the dental fossil evidence found in East and

South Africa, there are two adaptive groups which can be
extended to families. These two adaptive groups are gracile
and robust. They are quite distinct in morphological,
ecological relationship and behavior. Gracile group is
Australopithecus whereas Robust group is Paranthropus.

He sees a dichotomy in cranio – dental form

separating these two Australopithecine groups. Robust group
has the large post canine teeth crowns and its thick canine
has larger occlusal surface, well developed roots and
relatively flat occlusal surface (greater enamel has been
damaged). Crownding and size reduction of the front teeth,
point to a primary dietary function of crushing and grinding.
The massiveness of the entire masticatory apparatus
including the musculature and the wear of the teeth indicate
a diet of rough material which needed much chewing, hence
robust was herbivorous or vegetarian. Gracile forms show
none of these features, rather their post canine teeth are
smaller and anterior teeth would be substantial until tool
making had reached a fairly advanced level.

Age and Antiquity of place:

The Taung cave once considered to be very ancient

actually seems to be the most recent one, less than 0.9
million years ago. The specimen may represent one of the
last surviving members of the genus Australopithecus. The
absence of suitable materials precludes the use of Radio-
active dating in South Africa. A recent attempt of dating in
South Africa on the basis of geological data has resulted the
following dates:

Makapansgat – 3.7 million years ago

Stenfontein – 3.3 million years ago
Swartkans – 2.6 million years ago
Taung – 0.9 million years ago

In Olduvai Gorge pre historic volcanic activities

provided abandoned material for the application of Radio-
active dating techniques. The Australopithecus remains are
dated by potassium argon method and placed between 1.9
and 1.1 million years. Sites of the Omo valley has been
dated between 2.75 and 2.5 million years, the Hadar
material is dated between 3 to 3.5 million years and the
Lake Turkana is around 3 to 1 million years. However gracile
Australopithecus from other sites of East Africa such as
Middle Awash and Lothagam extend the age range of this
group of fossils to 4 million years and beyond perhaps to 5
million years.

Characteristic s of Australopithecus africanus:

Skull: Taken as a whole, the skull is a combination of

small brain case and large jaws. The brain case lacks high
vertical forehead of Homo sapiens and the high roundedness
of the skull vault. This gives a simian appearance. But in
bone feature it contrasts with pongidae and matches with
hominidae.
i. The supraorbital height index shows that the relative high
exceeds range of variation in anthropoid ape and actually
comes within the range of hominid skull.

ii. The occipital torus and the inion occupy a low level as in
hominid skulls. In adult apes this occipital torus forms a
crest high up the occipital aspects of the skull, thus
extending considerably the nuchal area for attachment of
neck muscles. In Australopithecus the nuchal area is
restricted as in homo.

iii. In Australopithecus the occipital condyles are forward in

position relative to the total length of the skull and the
auditory aperture. The occipital condyles of pongidae are
behind the midpoint of the cranial length and also behind the
auditory apertures.

iv. In all the Australopithecus skulls in which mastoid region

are sufficiently well preserved, there is a well marked
pyramidal process typical of hominid form.

v. The brow ridges are poorly developed compared to that of

the apes.
vi. The facial skeleton is however, large in relation to the
brain case.

vii. The cranial bones of Australopithecus robustus are

thicker than the Australopithecus africanus and the sagittal
crest is developed. The zygomatic arches are expanded and
flared.

viii. The jaws are also relatively large but no simian shelf.

Cranial capacity: In cranial capacity, the range of

variation is quite considerable. The skull of Australopithecus
afarensis and Australopithecus africanus ranges from 400 to
500 cc and Australopithecus robustus ranges from 410 to
530 cc. Thus the general endocranial size of Australopithecus
does not differ markedly from those of gorilla and
chimpanzee. However in relation to the body size
Australopithecus shows larger brain capacity proportion than
the apes.

Dentitions: Australopithecus dentition is essentially of

hominid type. In all the adult specimens the dental arcades
is evenly curved as in Homo sapiens with no diastimic
intervals. The canine is reduced in size and spatulate in
forms. Canines and incisors are almost in the same level.
The anterior upper premolars have two roots, the anterior
lower premolars are non sectorial and have one root
(sectorial and two roots in apes). There is good evidence for
the study of the immature specimens that the order of
eruption of permanent teeth agrees with the hominidae. In
Homo sapiens the canine erupts before the second molar.
This is reverse in the apes.

Pelvis: The total morphological pattern of the pelvis

of Australopithecus is hominid.

i. The anterior inferior iliac spine is strongly developed.

ii. The ilium is much relatively broader than in the apes. The
broad ilium lengthens the attachment of the gluteus muscles
that makes important in maintaining balance of the trunk on
the legs. The gluteus maximus becomes a fourfold extension
muscle which is needed for erect bipedal locomotion.
Whereas in monkeys and apes the gluteus maximus is an
abductor muscle.

iii. The posterior extremity of the iliac crest is extended

backward and downward in the sacral area.
iv. The angle of the sciatic notch (depression) is more acute
in the pelvis of man and Australopithecus than that of the
great apes. This is resulted in part due to development of
prominent ischial spine.

v. Ischial tuberosity is relatively high in man and

Australopithecus and closer to acetabulum than that of the
apes.

vi. Sacrum is shifted upward and closer to the acetabulum

forming more or less a basin or funnel shaped pelvis which
indicates the character of erect posture.

In all these characters the pelvic bone of

Australopithecus contrasts with the apes and shows pattern
for erect bipedalism. However the pelvis of Australopithecus
is not fully developed like that of the modern man. Ischail
tuberosity is not as quite closely approximated to the
acetabulum as it is in Homo sapiens. The anterior superior
spine extends further forward.

Limb bones: In addition to the pelvis, the

Australopithecus finds include many fossilized bones of leg,
hand and feet. One group from Olduvai Gorge includes
twelve of the major bones of a single foot and so perfectly
preserved that the details of the foot are readily
reconstructable. The foot of Australopithecus is much smaller
than a human foot. But the metatarsals are hominid and the
big toe points forward and not splayed out. The carpe bones
and phalanges found in Olduvai Gorge also show hominid
characters. Two specimens of the lower part of femur found
at Stenfontein have been described. They show a
combination of features such as the obliquity of the shaft,
the alignment of the condyles, the forward prolongation of
the intercondyler notches which confirm to the hominid
femur. Upper extremity of one specimen, however shows
certain pongidae features, such as relatively small size of the
articular head. A tibia and fibula found in Olduvai have
relatively straight shafts conforming to hominid character.

Difference between Australopithecus africanus and

Australopithecus robustus:
Character Australopithecus africanus Australopithecus robustus

Height 1.1 – 1.4 m. 1.2 – 1.4 m.

Weight 30 – 60 kg. 40 – 80 m.

Physique Light build, probably Very heavy build,

relatively long arms, relatively Long arms;
more human features; marked sexual
Probably less sexual dimorphism.
dimorphism.
Brain size 400 – 500 cc 410 – 530 cc

Skull form Low, flat forehead, Prominent crest on top

brow ridges less and back of skull,
prominent. long broad flattish face,
strong facial buttressing.

Jaw teeth Small incisor like Very thick jaws, small

canine, no gap incisors and canine,
between upper incisors large molar like premolar,
and canines, larger molars. very large molars.

Phylogenetic Position:

Currently there are three main phylogenetic trees

(A,B,C) each with its own cadre of proponents.

In figure A given by Johanson and White, the phylogenetic

tree places Australopithecus afarensis to as ancestral to the
later Australopithecines on one hand and the homo line on
the other. It gives homo line a late start i.e after 2 million
years.

In figure B given by L.S.B. Leakey, the common ancestor

of homo lineage and Australopithecine lineage diverge quite
early. And certainly by that line Australopithecus afarensis is
not the common ancestor of Homo and Australopithecus.
 The figure C is the combination of A and B where afarensis
is accepted as being ancestral to Australopithecines africanus
and it gives rise to the homo line on the one hand and
another Australopithecus robustus on the other (Here
Australopithecus africanus may have been a transitional
form which lead to the emergence of Homo habilis).

Conclusion:

The problem of whether Australopithecus africanus

represent early grade in homo liniage or a small brain
hominid arising as a separate product of Ramapithecus
radiation is yet to resolve. At the same time we also do not
know how the two dimorphic forms i.e. gracile and robust
Australopithecines are to be classed phylogenetically.
Whether they reflect polytypic nature of single taxon or
systematic enough to concieve as two taxa is still a question.

There is no generally accepted phylogenetic tree for

human evolution. There are several proposal branching (A, B
and C) perhaps the major distinction between them is
whether homo is perceived as late arrival (A and C) or as
early arrival (B and D).
 In some phylogenetic, robust is consider to be on the
same evolutionary line with Australopithecines and some
consider robustus to be separate from the earlier gracile
species (D) in which Paranthropus robustus/promethecus is
equivalent to Australopithecus robustus and Homo africanus
equivalent to Australopithecus africanus.

A third point to note is whether Australopithecus africanus is

ancestral to homo (C and D) or is a side issue (A and B).

Frequently asked questions:

Q.1. Why are the genera Australopithecus divided into

two species?

Ans: At first, several discoverers of the various

Australopithecus fossils named four to five different genera,
but now the consensus of scientific opinion recognizes one
genus Australopithecus and two species, one gracile form
represented by Australopithecus africanus and other robust
form represented by Australopithecus robustus, originally
called paranthropus. This division is made on the basis of
their morphological feature. The gracile form are slenderly
built and smaller; gracile form have probably relatively long
arm, probably less sexual dimorphism, high forehead,
shorter face, brow ridges less prominent. The incisors are
also small with no gap between upper incisor and canines
and have big molars; cranial capacity ranges from 410-530
cc. The robust form are large and roughly built. They have
relatively long arm with moderate sexual dimorphisms, crest
on top of skull, flattish face. The robusts have thick jaws,
small incisors and canine, very large molars; the premolar is
also large like molars. The cranial capacity ranges from 410-
530 cc.

Q.2. What do you mean by T. Robinson Dietary

hypothesis?

Ans: Going by the dental fossil evidence found in East and

South Africa, there are two adaptive groups which can be
extended to families. These two adaptive groups are gracile
and robust. They are quite distinct in morphological,
ecological relationship and behavior.

T. Robinson sees a dichotonomy in cranio-dental form

separating these two Australopithecines groups. Robust
group has the large post canine teeth crowns, thick enamel,
larger occlusal surface, well developed root and relatively
flat occlusal surface (greater enamel has been damage).
Crownding and size reduction of the front teeth points to a
primary dietary function of crushing and grinding. The
massiveness of the entire mastigatory apparatus including
the musculature and the wear of the teeth indicate use of a
diet of rough material which needed much chewing. Hence
robust was herbivorous or vegetarian. Gracile form shows
none of these features rather their post canine teeth are
smaller and anterior teeth larger. The needs for these in
meat eating would be substantial until tool making had
reached a fairly advanced level.

Q.3. What is the position of Australopithecus in the

line of human evolution?

Ans. Different scholars have given different opinion about

the position of Australopithecus in the line of human
evolution. According to Johanson and White Australopithecus
afarensis is regarded as the common ancestor of
Australopithecine and Homo. Australopithecus afarensis rise
to Australopithecus africanus and to Homo in one hand and
directly to Australopithecus robustus in the other hand. Here
Australopithecus africanus act as a transition form from
Australopithecine to Homo.

According to L.S.B. Leakey, the common ancestor of

both homo lineage and Australopithecine divided quite early.
He considers Australopithecus afarensis as not the common
ancestor. The homo lineage starts separately after 3 million
years and Australopithecus a little bit early but also only 3
million years.

Glossary:

Allometric - Differential growth rates of various parts of an

organism showing the shape of changes as a result of size
increase.

Anthropoid – A member of the primate, suborder

Anthropoidae (old and new world monkeys, apes and
humans). Alternative informal names are semian or higher
primate.

Apes – The primate group that have no tail, like gibbons,

orangutans, gorillas and chimpanzees.

Bipedalism – Walking on hind limbs, especially in the

upright, human way.

Canine – One of the pointed teeth at the corner of the

mouth.
Dimorphism – Two distinctive forms e.g. male and female
of a species.

Enamel – The hard white material containing over 96

percent apatelic calcium phosphate that covers the outer
surface of crown of teeth.

Extinction – The disappearance of species.

Fossil – Any preserved remains or traces of past life more

than about 10,000 years old, embedded in rock either as
mineralized remains or as impressions, casts or traces.

Occlusion – The position of the teeth when the jaws are

closed and their biting surfaces touch or occlude.

Phylogenetic tree – A schematic diagram of the evolution

or genealogical relationship among a group of species.

Potassium-Argon dating – A radiometric method for

dating volcanic rock based on the rate of decay of the
isotopes potassium 40 to argon 40.
References:

1. Campbell G. Bernard: Human Emerging. Scott Foresman

and Company, Boston London.

2. Clark W.E Le Gros, 1978: The Antecedents of Man.

Edinburgh University Press, George Square Edinburgh.

3. Comas J., 1972: Manual of Physical Anthropology. CC.

Thomas, Spring Field.

4. Harrison G.A., H.S. Weiner, M. Tanner, Barnnicot,

Reynolds, 1977: Human Biology, Introduction to Human
Evolution, Variation Growth and Ecology. Oxford
University Press.

5. Janusch, John Buettner, 1969: Origin of Man, Physical

Anthropology. Wiley Eastern Private Ltd. New Delhi.

6. Jones Steve, M. Robin, D. Pilbeam, 1992: Cambridge

Encyclopedia of Human Evolution; Cambridge University
Press.
Summary:

Australopithecines are the hominid fossils which are

abundantly found in Africa around 4 to 2 million years ago.
The fossil is discovered by Raymond Dart for the first time
in 1924 at Taung in South Africa. Others are Robert Broom,
L.S.B Leakey, C. Johanson etc. who have discovered from
different sites of South and East Africa. Earlier
Australopithecines fossils are grouped into four to five
different genera, but now the consensus of scientific
opinion recognizes one genus Australopiothecus and two
species Australopithecus africanus (gracile form) and
Australopithecus robustus (robust form). Considering all the
features such as dentitions, cranial capacity, limb bones,
pelvis etc. the Australopithecines is purely a hominid. The
phylogenetic as given by Johanson & White occupied
Australopithecus as the common ancestor of the later
Australopithecus on one hand and the homo lines on the
other hand. Again Leakey is of the opinion that the common
ancestor of Australopithecus and Homo diverse quite early.