Lab exercise 12.3 anthropology

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LAB EXERCISE 13.3
Station 1: Australopith Postcrania (Alternative to Specimens: Figures A and B on the next page;
materials or figures from Station 2 of Lab Exercise 13.2)
1. Compare postcranial bones of Australopithecus afarensis or another australopith to those
of an ape and a human, and fill out the table below. Answer from a comparative
perspective. For example, for orientation of iliac blades in A. afarensis compared to an
ape you might say, “more laterally placed,” while for A. afarensis compared to a human
you might say, “slightly more posteriorly placed.”
A.afarensis
Compared to an
Ape
A.afarensis
Compared to a Human
Pelvis Lateral orientation, long and
skinny
Very broad
Ilium shape and length Curved outward Curved inward
Orientation of iliac blades Posterior Lateral
Size of anterior inferior iliac
spine
Larger anterior inferior iliac
spine
Smaller anterior inferior
iliac spine
Femur Large Smaller
Bicondylar angle? Absent Present
Femoral head orientation Posterior orientation Lateral orientation
Height of femoral head
versus greater trochanter
Have a greater trochanter
than the height of the
femoral head
Greater femoral height than
the trochanter
Size of linea aspera
Not that long Located on the posterior
fermur longer
2. Overall, are the A. afarensis pelvis and femur more similar to apes or to humans? What
evidence do you see, if any, for bipedal adaptations in A. afarensis?
The reduced trochanter and increased femoral height with the bicondylar angle allow for
easier bipedal adaptations and balance.
Station 2: Australopith Cranium and Dentition (Alternative to Specimens:
Figures A through D on the next page and Figures 13.10 to 13.14)
1. Compare the cranium and dentition of Australopithecus afarensis to those of an ape and
a human, and fill out the table below. Answer from a comparative perspective. For
example, for position of foramen magnum you might say, “more anterior” compared to
an ape, but “more posterior” compared to a human.

2. A.afarensis
Compared to an ape
A.afrensis
Compared to a Human
Amount of prognathism Much Little or none
Canine shearing complex
(present or absent)
All components present Absent
Canine size Larger Smaller
Diastema Present Absent
Sectorial P3 Present Absent
Shape of chin
area/mandibular symphysis
(recedes back? vertical?
actual chin?)
Posterior : simian shelf Anterior :chin
Size of braincase—smaller or
larger (relative to overall
cranium size)
Smaller with about 275-550
cc
Larger approximately
1300cc
Much vs. little postorbital
constriction
Lower Higher
Position of foramen
magnum—more anterior vs.
more posterior
More posterior More anterior
Shape of dental arcade—
rounded, squared,
rectangular; are tooth rows
parallel?
Rectangular Rounded
Do molars increase or
decrease in size from M1 to
M3?
Increase Decrease
Location of maximum skull
breadth (viewed from
back)— higher vs. lower on
skull
Much Little
2. Overall, is the A. afarensis cranium more similar to apes or to humans? In what way is it
more similar to whom?
It is more similar to the human as it has more similar physical features.
3. What about the dentition? In what way is it more similar to whom?
It has a smaller dentition and decreased size of teeth and it’s more similar to the
human dentition.
Station 3: Comparative Australopith Cranial and Dental Features (Alternative to Specimens:
Figures A through G on page 375 and Figures A through D on page 372)

3. 1. Compare the three representatives of australopiths and note your comparisons in the table
below.
A. afarensis A. africanus Robust australopith
Amount of
prognathism
Little or none Considerable Little
Canine shearing
complex, or remnant?
(large canine size,
diastema, sectorial
P3)
Absent Present Absent
Height of skull – how
much skull is
superior to the
supraorbital ridge?
Inferior Superior Inferior
Sagittal crest? Present Mostly Present and
pronounced in males
Shape of facial
profile— “scooped”
out, flat, etc?
Flat kind of and little Scooped –out with
facial profile more
proganthic
More orthognathic ,
flatter , little
prognathism
Shape of chin
area/mandibular
symphysis (recedes
back? vertical? actual
chin?)
Anterior :chin More gracile not
flared
Very robust and flare
outward
Size of braincase
relative to face—
which takes up more
space on the
cranium?
Larger Lower Higher
Much vs. little
postorbital
constriction
Higher Little Much
Shape of dental
arcade— rounded,
squared, rectangular;
are tooth rows
parallel?
Rectangular Squared More rectangular
Do molars increase or
decrease in size from
M1 to M3?
Decreased Large Smaller
Robusticity of
zygomatic arches
Not flared Not flared Flared outward
Flare of zygomatic
arches (how far out
A little curved Do not curve much Curved outward

4. from the face do they
curve?)
Location of
maximum skull
breadth
More pronounced on
the lower
On the upper side On the lower side
2. Which of these forms do you think looked most like the common ancestor of the human
line; that is, which appears to have the most ancestral, or primitive, traits? Which features
prompt you to answer the way you did?
The A. africanus is similar to the human and has the most primitive traits, if you compare
the braincase and the skull sizes they are bigger and more defined than that of the human.
3. Which of these forms is most similar to humans? In what way(s)?
Robust australopith is more similar to the human and is more likely to be an ancestor of
the humans. Due to the size of the braincase, skull features and similarity of the zygomatic
arches.
4. For the robust australopiths, what do you think the molar tooth form and size, degree of
zygomatic flare, and presence of sagittal crest are related to?
I think it’s more related to the human in terms of the different features.
Station 4: Tooth Proportions (Measure the Specimens from Stations 2 and 3)
1. The relative size of the anterior and posterior dentition has changed through time and is
dependent upon dietary adaptations. Tooth proportions can be measured to track that
change. Measure the width (side to side) of a central upper incisor and of an upper second
molar (lingual side to buccal side). Then calculate an index to obtain a ratio of incisor-to-
molar width.
Incisor width * 100
100 Molar width
Incisor width M2 width Index
Chimpanzee 9.2 7.6 1.21
A. afarensis 9.1 7.9 1.15
A. africanus 9.05 8.0 1.13
Robust australopith 7.84 7.4 1.06
Modern human 9.26 8.63 1.07
2. What did this tell you about tooth proportions—the relative size of incisors and molars?
Do any of these specimens group together with similar measurements (or similar
descriptions)?

5. The tooth proportions are useful in classification of the different primates and type of
species.it aslo allows for various grouping and categorization of similar species and
evolutionary change.
3. Given that the ape is presumably the most similar to the common ancestral condition, and
A. afarensis is the oldest australopith, and humans obviously the most recent, can you say
anything about trends in tooth proportion over time?
The trend in the tooth proportion from the above data shows a decrease in index and size. The
teeth have become smaller and closer in size.
Station 5: Comparison of Young Individuals (Alternative to Specimens: Figure Below and
Figures from Lab Exercise 13.2, Station 1)
1. Compare the Taung child, designated as Australopithecus africanus, with the modern
fetal human skull and young ape in Lab Exercise 13.2, Station 1. Why do you think
the discoverer of the Taung child, Raymond Dart, insisted that the Taung skull was on
the human, not the ape, line? What features may have led him to this conclusion?
Keep in mind that this individual was at least three years old.
In that year, remains of the young individual the “Taung child”was brought to Raymond
Dart, who immediately recognized its significance as the first fossil used to establish that early
humans existed in Africa.By this time members of these species have long been referred to as
gracile australopiths to distinguish them from the robust group. It took many years for the
scien- tific community to widely accept Australopithecus as a member of the human line,
largely because it was held up to an earlier “find” from England and was found lacking in
comparison.