Student worksheet

Thought-starter: What other animals use tools?

Introduction - How are we different to animals?

Look at the images below comparing animal feet and arms/wings with human feet and arms. What are the significant differences and why do you think these exist? How and why did they evolve in these ways?

When studying the evolution of humans, we can see that there were several significant steps on the way to becoming modern humans. One of these is brain size, another is the shape of our skull and jaw, another is the slope of our legs and our ability to walk bipedally, and another is the use of tools.

The use of tools is important because it shows that our hands have evolved enough to grip these tools.

In this activity you will examine adaptations of the human hand by looking at your own hand and comparing your hand to the hands of other animals.

Activity 1. Adaptations of the human hand

Step 1.

Hold one of your hands out in front of you (hold out the hand you DON’T write with) with your palm face down and your fingers spread out. Observe the position of the thumb compared to the fingers, and write a description of these differences.

Step 2.

Turn your palm upwards and touch each of your fingertips with your thumb. Experiment with moving your thumb around. Observe how your thumb can move and write a description of this.

Step 3.

Pick up a ruler in your hand and hold it as you would a hammer. This is called a power grip. Describe how your thumb helps you with holding the ruler.

Step 4.

Hold a pen/pencil for writing. This is called a precision grip. Describe how your thumb helps with this grip and how the position of the thumb differs between the power grip and the precision grip.

Step 5.

The trapezium bone enables the thumb to touch your little finger. Hold your hand with the palm facing upwards and move your thumb to touch your little finger. Observe the direction the thumbnail points before, during and after you move it. Write a description of your observations.

Analysis

1. Why do you think the grip explored in Step 3 is known as a power grip?

2. Why do you think the grip in Step 4 is known as a precision grip?

3. Using the image of the hand above, identify the trapezium. Can you now identify the trapezium on your own hand?

4. How do you think the adaptations of the hand have aided object manipulation?

Activity 2. Without an opposable thumb

Step 1.

Turn to your partner and ask your partner to bind one of your hands so that your thumb is tight against the side of your hand touching the base of your forefinger.

Step 2.

Experiment with the power grip and the precision grip. Spend several minutes trying to complete other simple tasks, such as opening books or cupboards, typing on the computer, picking up a sheet of paper or eating (or pretending to).

Step 3.

Bind your partner’s hand in the same way so they can experiment with the power grip, precision grip and other actions.

Step 4.

Write a description of your experiences without the use of an opposable thumb.

Analysis

1. How do you think the adaptations of our hands have aided our evolution?

2. Speculate about how human evolution might have been different if our hands had evolved without an opposable thumb.

3. Speculate about the future evolution of our hands given that for most of us technology is now a bigger part of lives than holding hammers or even holding pencils. For example, some people have speculated that our thumbs will change to become more adapted to texting.

Activity 3. Comparing homologous structures in humans

Step 1.

Remove the shoe and sock from your left foot. Describe the position of the big toe and other toes.

Step 2.

Turn your foot and observe the instep of your foot (or if that’s too hard, ask to look at someone else’s instep). Observe the shape of the foot from heel to toe and describe what you see.

Step 3.

Look at a skeleton of the foot and the x-ray of a foot and describe how the foot looks from the side.

Step 4.

Again looking at the x-ray and skeleton, describe the heel and the differences between the toes.

Analysis

1. How do the positions of the big toe and the thumb compare?

2. Is the big toe as important to the functionality of the foot as the thumb is to the hand? Explain.

3. Could the heel, metatarsal and big toe be considered adaptations of the foot for walking? Explain your answer.

4. Describe how you think the same homologous structures could evolve into both hands and feet.

5. Speculate about the future evolution of our feet given that we are living more and more sedentary lives.

Evolution - Homologous Structures in Humans

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