Studying Living Organisms

Thumbs Up, Thumbs Down: Grasping the Idea of Evolution

Susan S. Plati

Target age or ability group:	Middle and high school
Class time required:	One 45-50 minute class period.
Materials and equipment:	For the class: Roll of duct tape or masking tape For each pair or group of students: pencil and paper chalk and blackboard clothing with buttons clothing with zipper loafers, sandals, or shoes with no laces shoes with laces straight back chair coins of various sizes plastic drinking glass chopsticks other objects of varying size and shape door with doorknob
Summary of activity:	Students compare their performance of a series of tasks using their thumb and fingers to their performance of the same tasks without the use of their thumb. The class discussion that follows the activity defines and discusses the role of fine and gross motor skills and speculates on the role of the opposable thumb in primate evolution.
Prior knowledge, concepts or vocabulary necessary to complete activity:	Basic knowledge of the mechanism of evolution, selection, and adaptation from previous activities and discussion will be needed. This lab exercise can be used to define both fine and gross motor skills after the activity is completed.
Teacher Instructions	You may wish to follow the teaching sequence outlined below so that students can complete the activity in a single class period. Have your students read the instructions and prepare their data table before coming to class. You may then introduce the activity with a brief discussion about characteristics that make us human. Get the students to generate a lot of ideas, placing key words on the chalkboard. Indicate that they will revisit the list for a more lengthy discussion after they complete the thumb activity. Have students work in pairs or groups for the activity. In this way they can compare their individual results to the members of their group or their partner during the activity. This should serve to facilitate the post lab discussion that will take place upon completion of the activity. During this post lab discussion you may wish to have the class summarize their results and the significance of these results and begin a discussion of the questions that are in the analysis section of the lab instructions. You may further wish to go back to the list that the class generated at the beginning of the class period and expand on the discussion of what makes us human. It is interesting to speculate on how our well developed brains have helped us to use our opposable thumb (and ultimately our fine motor skills) to the advantage of our species. This ultimately may lead to a discussion of how human imagination coupled with the development of fine motor skills might have led to the development of various creative endeavors in science, art, music, literature, technology. Here is another opportunity to explore the interaction of culture (environment) and heredity (genes).

Only apes and primates have hands capable of grasping objects. The grasp is made possible by the opposable thumb, so called because it moves opposite to the rest of the fingers. In humans, the thumb can move farther across the hand than in any other primate. In this experiment you will compare your performance of a series of tasks using your thumb and fingers together with your performance of the same tasks without the aid of your thumb.

Materials and Equipment:

For the class:
Roll of duct tape or masking tape

For each pair or group of students:
pencil and paper
chalk and blackboard
clothing with buttons
clothing with zipper
loafers, sandals, or shoes with no laces
shoes with laces
straight back chair
coins of various sizes
plastic drinking glass
chopsticks
other objects of varying size and shape
door with doorknob

Procedure:

Working in groups or with a partner, each person should perform the experiment discussing the results and observations as you proceed.

1. Observe your hand. Notice especially the relationship of your thumb to the rest of your fingers and the rest of your hand. Note that your thumb can move in a number of directions and angles. Record a description of the range of motion of your thumb in your lab notebook or data sheet.

2. Perform the following list of tasks as you normally would, using your thumb and fingers. Pay special attention to your thumb and its involvement in these tasks. Enter your observations on the data table about whether it was difficult or easy to do each task and what the level of "thumb involvement" was.
   1. Write your name with a piece of chalk on the chalkboard.
      
   2. Write your name with a pencil or pen on a small piece of paper.
      
   3. Unbutton and rebutton an article of clothing that has buttons.
      
   4. Use a zipper on an article that of clothing that has a zipper.
      
   5. Put on a pair of shoes and tie the laces.
      
   6. Put on a pair of shoes with no laces.
      
   7. Pick up a straight-backed chair.
      
   8. Pick up several coins.
      
   9. Pick up a drinking glass.
      
   10. Use chopsticks.
       
   11. Open and close a door using the doorknob.
       
   12. Pick up other objects
       
   Data Table

   	Hands Untaped		Hands Taped
   Task	Ease	Thumb Involvement	Ease
   a. name with chalk
   b. name with pencil
   c. buttons
   d. zipper
   e. tie shoe
   f. slip on shoes
   g. pick up chair
   h. pick up coins
   i. pick up glass
   j. use chopsticks
   k. open and close door
   l. _______________
   m. _______________

3. Working with a partner, have each partner tape the other person's thumbs to the palms of each hand with masking tape or duct tape as shown in the illustration. Be careful not to wrap the tape too tightly and cut off the blood circulation to your hand!
   
   
   
   
   
   
   
   
4. Repeat the tasks listed in step two under Procedure with your taped hands. Pay particular attention to any difference in the performance of the tasks. Enter your observations in the data table as before.

Analysis and discussion:

1. Which tasks required the least "thumb involvement"? Which tasks required the most? Explain your answer.

2. Of the tasks you performed, which required fine motor skills (those requiring small subtle hand movements) and which required gross motor skills (those involving larger movements using arm and back muscles)? Is there a correlation between thumb use and the type of motor skills involved? Explain your answer giving evidence from your data and that of others in your class.

3. Many scientists believe that the opposable thumb has helped humans adapt to their environment and survive. Using your data as a guide, write several paragraphs to explain some of the ways in which the use of the thumb enables humans to better survive in their environment.

4. Speculate on how the well developed human brain may have helped our species make creative use of its fine motor skills.

Reference

Plati, Susan. How Important is Your Thumb? More Science Experiments on File. New York: Facts on File, 1991.

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