Student Name ________________________________ Class _________________________________
Others on Team _____________________________________________________________________
HOMINID SKULL COMPARISON Introduction In this activity you will examine skull casts and other evidence to investigate and evaluate evolutionary relationships among living and extinct human relatives.
Materials per class: 1 skull cast of each of the following: Homo sapiens (modern human), Pan
Procedure: PART A – Comparison of Modern Apes and Humans
Using skull casts, photographs, and other visuals of humans, chimpanzees, and gorillas, your teacher will engage you in a discussion, during which, you compare these modern hominids. During this discussion, you should make a list of the features these hominids share and those features that make them differ.
Procedure: PART B – Comparing Modern and Extinct Hominid Skulls In this part of the activity you will make detailed observations and measurements of skull casts of seven modern and extinct hominids. You will then use your data to determine a hominid evolutionary tree hypothesis. Your data will also provide a basis for drawing some conclusions about patterns of hominid evolution.
1. Your team will move from station-to-station as you examine the skull casts. At each station you will find
a skull, metric ruler, protractor, and caliper. A few “rules” should be followed:
Do not make pencil or pen marks on the skulls.
Be careful with the skulls. They are expensive reproductions that are breakable.
Be sure to take turns in making the measurements.
Measure in millimeters (mm). Round off to whole numbers.
2. Complete the “Hominid Skull Comparison Data Table” as you move from station-to-station. Refer to
the “Hominid Comparison Checklist” for a description of each hominid characteristic you observe.
HOMINID SKULL COMPARISON CHECKLIST
1. FOREHEAD: Does the forehead (frontal bone) look more vertical or does it slope backward?
2. CHIN: Does the chin stick out or does it recede back?
3. SAGITTAL CREST: A sagittal crest is a bony ridge that runs from front to rear on top of the cranium. Is it small, medium, large, or absent?
4. FACIAL PROGNATHISM: How much does the snout protrude when looking at the skull from the side? Is the protrusion large, medium, small or absent?
5. BROWRIDGE: The brow ridge is a heavy mass of bone directly over the eye orbits. Rate it large, small, medium.
6. DENTAL ARCADE: This refers to the shape of the arrangement of the teeth in the jaw when looking directly at the chewing surface of the teeth. Does the arrangement form a parabolic (rounded) shape with a relatively continuous outward curvature or is the arrangement rectangular with the premolars and molars in parallel rows?
a = incisors
b = canines
c = premolars
d = molars
7. CANINE TOOTH: What is the length in millimeters of the exposed part of the upper canine tooth?
8. DENTAL FORMULA: Record the number of incisors, canines, premolars and molars present in the upper jaw. (ICPM) 9. CANINE DIASTEMA: Is there a gap present on the upper jaw between the canines and incisors?
10. ANGLE OF INCISOR: Do the incisors rise vertically from the jaw or do they slant out?
11. FORAMEN MAGNUM: The foramen magnum is a large opening in the back or bottom of the skull through which the spinal cord enters the cranium. Determine if it is more to the rear or towards the bottom of the skull.
12. WIDTH OF CRANIUM: Use the caliper and ruler to determine the maximum width of the brain case. Measure from temple-to-temple and record your answer in millimeters.
13. LENGTH OF CRANIUM: Use the caliper and ruler to determine the maximum length of the brain case. Measure from the forehead to the back of the skull.
14. FACIAL SLOPE: Use the protractor to measure the angle make by the face and the upper jaw when viewed from the side.