Physical Anthropology
Comparing Hominids
Introduction: It is widely believed that
Australopithecus africanus was closely related to the
ancestors of modern humans, including ourselves.
Some members of A. africanus eventually evolved
into Homo habilis, the first human species. In turn,
Homo habilis was the ancestor of Homo eragaster,
the ancestor to two lines of hominids, Homo erectus
and Homo heidelbergensis. H. heidelbergensis gave
rise to two homind species who lived at the same time
until one became extinct, Homo neanderthalensis
about 30,000 thousand years ago leaving only one
living hominid species, Homo sapiens.
Essential Question: What kinds of data can we use to
identify and organize fossil species of hominids to
illustrate how common ancestry and biological
evolution occur?
Objectives:
1. Compare major similarities and differences
between the skulls of Australopithecus sp., Homo
erectus, Homo neanderthalensis, and Homo
sapiens.
2. Infer evolutionary changes by comparing
qualitative and quantitative anatomical features of skulls.
Materials:
 internet access and/or skull casts
 Calipers (if using skull casts)
 Metric rulers
 copies of hominid and Australopithecus sp. skulls
 student handout
 calculators
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Procedure:
Part A: Qualitative comparisons of skulls
A. Examine the skull, face and forehead of the hominid casts and/or visit
http://www.indiana.edu/~ensiweb/lessons/skulls2.html and examine skulls h, f, e, and d
(Australopithecus sp., H. erectus, H. neanderthalensis and modern H. sapiens).
Compare physical characteristics of each of the fossil species relative to one another.
 Describe the forehead as more vertical or more sloping.
 Describe the face as larger and more projecting or smaller and straighter.
 Describe the brow ridges as larger or smaller.
Visit http://australianmuseum.net.au/Virtual-Skulls to examine the back of the hominid skulls
 Describe the maximum skull width, as seen from the back, as closer to the base, closer to the top, or
in between.
Record your observations in the table below.
Table 1: Comparative Skull Features Qualitative Data
Fossil Species
Forehead
more vertical or
more sloping
Face
larger and more
projecting or
smaller and
straighter”
Brow Ridges
larger or smaller
Maximum Skull
Width
closer to the base,
closer to the top,
or in between
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Australopithecus sp.
skulls “h”
Homo
neanderthalensis
skulls “e”
Homo erectus
skulls “f
Homo sapiens
skulls “d”
Part B: Quantitative comparisons of skulls
Let's take a closer look at the skulls and see if we can get some sort of measurements to back up our qualitative
observations. Scientists use three basic sets of measurements to compare skulls. These measurements are
described below. View the diagram of the skull below as you read through the meaning and calculation of these
measurements.
•
•
•
condylar position index (ratio of CD:CE x 100)
o important for maintaining balance when walking upright
on two legs (bipedal) and indicates how upright the
organism stood
o the more centered that the occipital condyles (location C)
are along the Frankfurt plane the more likely the hominid
stood upright
maxillary prognathism index (ratio of HE:DE x 100)
o Maxillary = related to the upper jaw bone
o Prognathism = how much top jaw protrudes
o indicates dietary changes in evolution
supraorbital height index (ratio of FB:AB x 100)
o used to measure the height of the eyes above the skull
o indicates overall cranial height (frontal lobe), this is an
indirect measure of the size and complexity of the
cerebrum.
Two of these measurements (condylar position index and maxillary prognathism index) use an area called the
Frankfurt plane (line DE). The Frankfurt plane is a line that passes from the bottom of the eye socket through
the top of the ear opening. This is the plane in which the head is normally carried during life. Run your finger
across the Frankfurt plane on your skull. The third measurement (supraorbital height index) indicates the
relative size of the brain. As you make the measurements, record the results in the table below.
Table 2: Comparative Skull Features Qualitative Data
Australopithecus
sp.
length CD (mm)
length CE (mm)
length HE (mm)
length DE (mm)
length FB (mm)
length AB (mm)
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Homo
neanderthalensis
Homo erectus
Homo sapiens
Data Analyses and Conclusions
Calculate the basic measurements used by scientists to compare hominid skulls.
Table 3: Comparative Skull Features Qualitative Calculations (show calculations, round to whole number)
Australopithecus sp.
Homo
neanderthalensis
Homo erectus
Homo sapiens
condylar index
CD/CE * 100
maxillary
prognathism
index
HE/DE * 100
supraorbital
height index
FB/AB * 100
By using the information you have recorded in your table and the display of skulls, answer the following
questions.
1. Reread the introduction and place your skulls in order from oldest to most recent.
Condylar Index Analyses
1. List the four Hominid skulls (Australopithecus sp, Homo neanderthalensis, Homo erectus, and Homo
sapiens) in order, from largest condylar index to smallest condylar index.
2. What inference can you make regarding size of the condylar index and the age of the fossil?
3. Explain the evolutionary significance of this relationship.
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Maxillary Prognathism Index
1. List the four Hominid skulls (Australopithecus sp, Homo neanderthalensis, Homo erectus, and Homo
sapiens) in order, from greatest maxillary prognathism to least maxillary prognathism.
2. What inference can you make regarding the percent of maxillary prognathism and the age of the fossil?
3. Explain the evolutionary significance of this relationship.
Supraorbital Index
1. List these same skulls in order, from the largest supraorbital index to the smallest supraorbital index
2. What inference can you make regarding the size of the supraorbital index and the age of the fossil?
3. Explain the evolutionary significance of this relationship.
Conclusion
1. As humans have evolved, try to describe, in one sentence, the three patterns of change illustrated by the
skulls you have examined.
2. What has happened to brain size and jaw size over 6 million years of human evolution?
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