Primate Adaptations: The Importance of the Opposable Thumb

Adaptations are inheritable characteristics that help organisms survive in the environments in which they live. One important adaptation in primates is the opposable thumb. Opposable thumbs enable primates such as monkeys to grasp tree branches effectively. Humans use their opposable thumbs to manipulate tools. This activity will help you see how important the opposable thumb is for humans.

Materials

Duct tape

Shoelace

Stopwatch

Activity

1. Place the shoelace on a table in front of you. Use the stopwatch to see how quickly you can pick up the shoelace, tie it in a bow, and place it back on the desk.
2. Now use the duct tape to tape the thumbs of both hands to the sides of your hands. (Taping your thumbs simulates hands with no opposable thumb.)
3. Repeat step 1 without the use of your thumbs.

Follow-Up Questions

1. How much time difference was there between tying the bow with your thumbs and tying the bow without thumbs?
2. List as many activities as you can think of that would be affected if humans did not have opposable thumbs.

Answers

1. Answers will vary, but it should have taken much longer to tie the bow when the thumbs were taped to the hand.
2. Answers will vary and can include writing, throwing a ball, swinging a bat, sweeping the floor, typing, or texting.

Extension

Another primate adaptation is binocular vision, which means there is slight separation between the two eyes to better view objects. Scientists believe this adaptation has enhanced primates' eye-hand coordination and the ability to judge distance. Test this claim by having one of your classmates hold two pencils in front of you at different distances. Quickly grab one of the pencils from him. Now repeat this with one eye closed. What does this tell you about the advantages of binocular vision?