Using the Human Evolution – Skull Analysis Gizmo™, you will discover some of the ways that skulls can be used to learn about human evolution. Start by comparing two modern hominids: a human and a chimpanzee.
An important index for measuring hominid skulls is the opisthion index. This index indicates the position of the foramen magnum in the base of the cranium. The opisthion index can indicate whether a hominid species was bipedal or not.
Question: How does the location of the foramen magnum indicate if a species was bipedal?
1. Measure: Select the Bottom view. To determine the opisthion index for humans and chimps, follow the steps below and answer the questions.• Turn on Click to Measure Lengths. Measure the distance from the opisthocranion to the opisthion, as shown below. Record the opisthocranion-opisthion distance.• Measure from the opisthocranion to the orale, as shown. Record the opisthocranion-orale distance.• To calculate the opisthion index, divide your first measurement by your second measurement. Multiply this number by 100.
Question: How does the cranial capacity compare amongst hominids?
Measure: To estimate the cranial capacity of each skull, measure the area of the part of the cranium that houses the brain. This part of the cranium is roughly behind the red line in the diagram. You can also use the other three skull images as a guide for measuring the rest of the skulls in the Gizmo.
After you measure the area of each cranium, multiply the result by 5. This will give you a very rough estimate of the species’ cranial capacity.