Activity: Comparing Primates - From Gorillas to Humans

Goal: To identify the changes that occurred among the early hominoids and the hominids of today.

Background Information: About 6 million years ago, the primates known as hominoids which include gorillas and chimpanzees gave rise to a small group of species now considered to be the closest relatives to humans. This small group of species is called hominids. Hominids, which include humans and closely related primates, are members of the human family known as Hominidae. Although these early hominids were not yet humans, they did take evolutionary paths that distinguish them from other hominoids. During their evolution, many changes have occurred to the basic skeleton of these hominids. In this activity, you will identify some changes that have occurred among early hominoids and the hominids of today.

Materials: metric ruler, drawings of hominid jaws and fingers, calculators, drawings of different jaws, drawings of different fingers

Procedure:

1.  What I Know: Write a sentence or two describing what you already know about how humans have changed over time. (You can use your experience with the activity Digging for Differences and your observations of the hominid skulls as examples.)

2.  Using the drawings of the hominid jaws to make measurements of the jaw index.

a.  Measure the width of the jaw by measuring the length of the line between the back molars.

b.  Measure the length of the jaw by measuring the line from the back of the mouth to the front teeth. Record these measurements for the human, Austalopithecus, and the gorilla on the data table.

c.  To measure the jaw index, multiply the jaw width by 100 and then dividing by the length of the jaw. This is the jaw index. Find the jaw index for each of the hominoids on the data table.

Data Table:

Hominoids / Width of Jaw / Length of Jaw / Jaw Index
Human
Australopithecus
Gorilla

3.  Using the drawings of the hominid fingers to make measurements of the thumb index.

a.  Measure the length of the thumb and the length of the index finger. Record these measurements on your data table for each of the hominids.

b.  To measure the thumb index, multiply the thumb length by 100. Divide by the index finger length. Record the thumb index for each of the hominoids on the data table.

Data Table:

Hominoids / Length of Thumb / Length of Index Finger / Thumb Index
Human
Australopithecus
Gorilla

4.  What I Did: Write a short description of the procedure.

5.  What I Observed: This is the data you collected on your data tables.

6.  What I Learned: Summarize what you learned from completing this activity. Be sure to write a paragraph that includes at least 5 sentences. It should refer to the goal of the activity and should provide examples from your data tables.

7.  What I Wonder: Pose a “why” or “how” question about what you may still want to know or wonder about this topic.

8.  Questions: Answer the following questions in complete statements.

a.  What trend did you observe regarding the thumb index for humans,

Austalopithecus, and gorilla? (Hint: Did the thumb index increase or decrease as hominoids become more advanced?)

b.  What trend did you observe regarding the jaw index for humans,

Australopithecus, and gorilla? (Hint: Did the jaw index increase or decrease as hominoids became more advanced?)

c.  Do you think Austalopithecus was a hominid with characteristics somewhere in

between those of gorillas and humans? Give evidence from your data to support your answer.

d.  Why is it an advantage for a human to have a longer thumb in relation to the index finger?

e.  Based on your observations, how did the jaw change over time?