Name: Samantha Simmon Date: 2/22/21
Student Exploration: Human Evolution - Skull Analysis
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: bipedal, canine, cranial capacity, cranium, evolve, foramen magnum, hominid, hominin, index,
maxilla, orbit, palate, skull
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Label one of the skulls below as human and the other as a chimpanzee skull.
Human Chimpanzee
2. What features did you use to identify which skull was human and which was chimpanzee?
The size of the jaw and the back part of the skull
Gizmo Warm-up
In 1924, a fossilized skull that looked very similar to a chimp skull was
discovered. But the skull most definitely did not belong to a chimp. The
location of the foramen magnum—a hole in the skull where the spinal
cord exits—indicated that the individual was bipedal, or walked on two
legs. This fossil was some of the earliest evidence of human evolution.
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.
1. Examine the Front view of the Homo sapiens (modern human) skull.
Then, use the Select skull menu to examine the same view of the Pan troglodytes (chimp) skull.
How do the skulls compare?
The chimp’s jaw is much larger than a humans and the size of its head is also smaller than a
human.
2. Now, examine the Bottom view of the two skulls. How do they compare?
The chimp has a longer jaw than the human jaw. The eyes are also bigger than the humans.
, Activity A: Get the Gizmo ready:
Foramen magnum ● Select the Homo sapiens (modern human) skull.
Introduction: Skulls, even from the same species,
can have a wide variety of shapes and sizes. To
compare skulls, scientists use measurements of
certain features to calculate indexes. An index is a
ratio of one measurement to another.
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 complete the table.
● Turn on Click to Measure Lengths. Measure the distance from
the opisthocranion to the opisthion, as shown at top right.
Record the opisthocranion-opisthion distance in the table below.
● Measure from the opisthocranion to the orale, as shown at
bottom right. Record the opisthocranion-orale distance in the
table.
● To calculate the opisthion index, divide your first measurement
by your second measurement. Multiply this number by 100.
Opisthocranion-
Opisthocranion-
Species opisthion distance Opisthion index
orale distance (cm)
(cm)
Homo sapiens 4 cm 15.5 cm 25.806452 cm
Pan troglodytes 2.5 cm 20.5 cm 12.317 cm
2. Analyze: The opisthion index is an indicator of where the foramen magnum is situated. The greater the
opisthion index, the closer the foramen magnum is to the center of the cranium. This position is usually
found in species that stand upright. A low value for the opisthion index occurs when the foramen magnum
is situated in the rear of the cranium. This may indicate that the species walked on its knuckles or on four
legs.
Using the index values you calculated, what can you conclude about humans and chimps?
Compared to chimps, humans stand very upright.
3. Gather data: Humans, chimpanzees, and the other great apes are hominids. Hominids evolved from a
common ancestor that lived about 13 million years ago. Hominins are hominids that belong to the lineage
Student Exploration: Human Evolution - Skull Analysis
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: bipedal, canine, cranial capacity, cranium, evolve, foramen magnum, hominid, hominin, index,
maxilla, orbit, palate, skull
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Label one of the skulls below as human and the other as a chimpanzee skull.
Human Chimpanzee
2. What features did you use to identify which skull was human and which was chimpanzee?
The size of the jaw and the back part of the skull
Gizmo Warm-up
In 1924, a fossilized skull that looked very similar to a chimp skull was
discovered. But the skull most definitely did not belong to a chimp. The
location of the foramen magnum—a hole in the skull where the spinal
cord exits—indicated that the individual was bipedal, or walked on two
legs. This fossil was some of the earliest evidence of human evolution.
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.
1. Examine the Front view of the Homo sapiens (modern human) skull.
Then, use the Select skull menu to examine the same view of the Pan troglodytes (chimp) skull.
How do the skulls compare?
The chimp’s jaw is much larger than a humans and the size of its head is also smaller than a
human.
2. Now, examine the Bottom view of the two skulls. How do they compare?
The chimp has a longer jaw than the human jaw. The eyes are also bigger than the humans.
, Activity A: Get the Gizmo ready:
Foramen magnum ● Select the Homo sapiens (modern human) skull.
Introduction: Skulls, even from the same species,
can have a wide variety of shapes and sizes. To
compare skulls, scientists use measurements of
certain features to calculate indexes. An index is a
ratio of one measurement to another.
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 complete the table.
● Turn on Click to Measure Lengths. Measure the distance from
the opisthocranion to the opisthion, as shown at top right.
Record the opisthocranion-opisthion distance in the table below.
● Measure from the opisthocranion to the orale, as shown at
bottom right. Record the opisthocranion-orale distance in the
table.
● To calculate the opisthion index, divide your first measurement
by your second measurement. Multiply this number by 100.
Opisthocranion-
Opisthocranion-
Species opisthion distance Opisthion index
orale distance (cm)
(cm)
Homo sapiens 4 cm 15.5 cm 25.806452 cm
Pan troglodytes 2.5 cm 20.5 cm 12.317 cm
2. Analyze: The opisthion index is an indicator of where the foramen magnum is situated. The greater the
opisthion index, the closer the foramen magnum is to the center of the cranium. This position is usually
found in species that stand upright. A low value for the opisthion index occurs when the foramen magnum
is situated in the rear of the cranium. This may indicate that the species walked on its knuckles or on four
legs.
Using the index values you calculated, what can you conclude about humans and chimps?
Compared to chimps, humans stand very upright.
3. Gather data: Humans, chimpanzees, and the other great apes are hominids. Hominids evolved from a
common ancestor that lived about 13 million years ago. Hominins are hominids that belong to the lineage
