ANTH 1500: Cladistics
Instructions:
Note the species of each of the provided specimens and record it in the table
below.
Determine whether each of the listed traits display either ancestral or derived
characteristics for each specimen.
Add up the total number of ancestral and derived traits for each specimen.
Canine
Size
Species
Pan troglodytes
Foramen
Mangum
Position
Large
Back
Ancestra Ancestral
l
l
Australopithecus
afarensis
Large
Underne
Ancestra ath
l
Derived
Homo erectus
Small
Derived
Small
Homo
heidelbergensis
Underne
ath
Derived
Underne
ath
Derived
Brow
Ridges
Small
400cc
Ancestr
al
Small
420cc
Ancestr
al
Big
Ancest
ral
Big
Ancest
ral
3
1
Big
1000cc
Derived
Big
Big
Ancest
ral
Big
1
3
1
3
Derived
Ancest
ral
Big
Small
0
4
Derived
Derive
d
Derived
Small
Homo Sapiens
Underne
ath
Derived
Derived
Cranial
Capacity
# of
# of
Ancestral Derived
Traits
Traits
4
0
In the space provided below, use your completed table to draw a cladogram
illustrating the ancestry & relationship of each of the provided specimens to one
another.
Terminology Handout
Phylogenetics: the study of evolutionary relationships among biological entities such
as species. Attempts to reconstruct evolutionary relationships by identifying
monophyletic groups of species that are descended from a common ancestor. These
groups are identified by the presence of shared derived traits (see below). An example
of a shared derived trait in hominin evolution is bipedalism.
Ancestral: In phylogenetics, a primitive (or ancestral) character, trait, or feature of a
lineage or taxon is one that is inherited from the common ancestor of a clade (or clade
group) and has undergone little change since.
Derived: In phylogenetics, a derived trait is a trait that is present in an organism, but
was absent in the last common ancestor of the group being considered. This may also
refer to structures that are not present in an organism, but were present in its ancestors,
i.e. traits that have undergone secondary loss like brow ridges in Homo sapiens.
Skulls examined in discussion:
Pan troglodytes
Australopithecus afarensis
Homo erectus
Homo heidelbergensis
Homo sapiens
Image source:
https://www.pathwayz.org/Tree/Plain/
APE+VS.+HOMININ+SKULLS
Basic observations
1. Prognathism: extent to which the jaw protrudes out in front of the face.
2. Brow ridges: more pronounced in earlier species to provide attachments points for
muscle.
3. Cranial Capacity (Brain size): cranial cavity increases over time and changes
shape, particularly in the frontal areas (development of a forehead) that is
associated with enhanced cognitive abilities. Note: on average, Neanderthals brains
were bigger than Homo sapiens!
4. Location of foramen magnum: hole in the base of the cranium that attaches to the
spinal column. Shifts forward, to center of cranium with shift to bipedalism.
5. Teeth: overall size of teeth and canines decreases through time in association with
shift in diet. The shape of the mandible/jaw also changes as the dental arcade
transitions from a U-shape to a more open parabola.
6. Length of cranium: the overall shape and relative length of the cranium changes
through time.
7. Post orbital constriction: a narrowing behind the eyes is more prominent in earlier
species.
8. Zygomatic arch: space where “cheek muscles” can attach decreased over time as
eating patterns change.
9. Nuchal crest: the ridge on the back of the cranium that serves as a point of
attachment for neck muscles. Over time it becomes less pronounced (e.g. less
angled and more rounded)
0
