In this lesson, students investigate hominid evolution. They learn the difference between a relative and an ancestor, study the emergence of bipedalism and the related physical adaptations and cultural ramifications, and chart patterns of hominid migration. Throughout the lesson, an emphasis is placed on the importance of fossil evidence in unraveling the history of our ancestors.
- Learn about fossil evidence for human evolution
- Identify major fossil groups:Australopithecus,Homo habilis,Homo erectus,Homo neanderthalensis, andHomo sapiens (modern and present)
- Understand molecular evidence for human evolution
- Learn about the genetic relationship between humans and our closest living relatives
- Identify major characteristics selected for in hominid evolution -- bipedalism and a large brain -- and the adaptive advantages of each
- Understand hypotheses about the evolution of bipedalism
- Learn about migration patterns of early hominids
- Three class periods
- Laetoli Footprints Video
- Laetoli Trackways Diagram Image
- Finding Lucy Video
- The Transforming Leap, from Four Legs to Two Document
- Walking Tall Video
- Riddle of the Bones Interactive
- Evolving Ideas: Did Humans Evolve? Video
- Origins of Humankind Interactive
- Hominid Fossil Data Sheet Document
- World Map Document
- Hominid Migration Discussion Questions Document
- Copies of handouts
- Laetoli Trackways Diagram diagram and backgrounder
- Colored pencils
- Colored pushpins
Before the Lesson
- Prepare for the lesson by making copies of the handouts and collecting the materials.
Part I: Laetoli Footprints
1. Have students watch the Laetoli Footprints video as an introduction to this lesson on human evolution.
2. Divide the class into teams of two, and distribute copies of theLaetoli Trackways Diagram diagram and accompanying backgrounder to each team. Ask each team to study and discuss the trackways and record their answers to the following questions:
- What creatures probably made the tracks?
- How were these creatures moving (walking, running, etc.)?
- What interactions, if any, do the tracks suggest?
- What is the evidence for your answers?
3. Conduct a classwide discussion, sharing different scenarios from each team and pointing out the evidence for each.
4. Engage students in a discussion about what footprints can tell us. For example:
- Do individuals with longer feet also have longer legs?
- Are people with longer legs taller?
- Are the number of strides a person takes in a given distance different when he or she is running or walking?
- Does the person's stride length change with speed? Would the same hold true for early hominids?
- Can patterns of the present give us clues to patterns of the past?
Part II: Walking on Two Feet
5. Have your class watch the Finding Lucy video and discuss the following questions:
- What evidence did Johanson use to show that Lucy walked upright?
- Why might bipedalism have been an advantage in early hominids?
- What changes in the environment might have exerted selective pressure?
- Why might larger brains have evolved after bipedalism?
6. Have students read the article The Transforming Leap, from Four Legs to Two. Discuss the following:
- What hypotheses do scientists give for the evolution of bipedalism?
- What anatomical changes were necessary for bipedalism to evolve?
- What cultural changes did bipedalism cause?
- How do recent fossil findings support the idea that bipedalism evolved long before large brains?
7. Continue your discussion of bipedalism by watching theWalking Tall video and comparing skeletons of the modern human and the chimpanzee. Ask:
- What modifications in the human skeleton allow us to walk upright?
- List the similarities and differences between human and chimpanzee skeletons.
- What problems do humans experience as a result of their upright stance?
- What advantages does it convey?
- Why can't the chimpanzee walk on two legs?
Part III: Fossil Findings
8. Have students visit the Riddle of the Bones Web activity. Tell them that in this activity they are going to be paleoanthropologists. Assign them to teams of four.
9. There are four dig sites in the Riddle of the Bones activity: Lucy, Hadar Skull, First Family, and Laetoli Footprints. Assign each team to a dig site. (It's OK that there will be more than one team per dig site.)
10. Tell each team to review the evidence at their site and answer the following questions:
- What kind of creature made this fossil?
- When did this animal live?
- What did it look like alive?
- How did it move?
- When was it found and by whom?
11. Have the teams write a summary of their findings, then discuss with the class how the fossils are related to one another.
Discuss as a class the following questions:
- What kinds of information about hominid evolution does the fossil evidence provide?
- What are the limitations of fossil evidence?
- What inferences about early hominids are made from the fossils?
Part IV: Hominid Evolution
12. Have students watch the Evolving Ideas: Did Humans Evolve? video as an introduction to the following activity.
13. Ask your class to visit the Origins of Humankind Web activity. Assign students to groups of two and give each group one or more of the following groups of questions, depending on the size of your class:
- Look at the family tree: Why are some of the branches labeled with question marks? Find another family tree on the Web or in your textbook. Note any differences. Why might the two trees be different?
- Look at the species gallery: What observations can you make about the changing shape of the hominid skull?
- Look at the timeline: When was the first hominid fossil found? Why is this earliest hominid controversial? (You may need to look for online articles to answer this question.)
- Why do some scientists considerHomo neanderthalensis to be part of the speciesHomo sapiens?
- When did bipedalism evolve? Which species was the first early bipedal hominid? What specific evidence supports bipedalism in early hominids? Which early hominid fossils provide the strongest evidence of bipedalism?
- When did the first evidence of tool use appear? In what species?
- Which was the first hominid to leave evidence of culture? What clues did hominids leave behind that reflected their cognitive abilities?
- What cultural adaptations allowedHomo erectus to expand beyond tropical and subtropical environments into the cooler climate of the temperate zones? Which hominids coexisted in time? Why and how do you think this was possible?
14. Reconvene as a class and discuss answers.
Part V: Hominid Migration
15. Introduce the next part by explaining that discoveries of fossil hominids around the world have helped scientists to determine not only the likely place of origin for the human species, but also a migration path throughout the world. Tell students that their assignment is to map this distribution.
16. Group students into five teams:australopithecine, Homo erectus,Homo neanderthalensis, and two Homo sapiens teams. Give each team one part of the fossil evidence from theHominid Fossil Data Sheet (PDF) and colored pencils to match their taxon code (Australopithecines -- red, Homo erectus -- blue, etc.). Point out that the early modern Homo sapiens data is divided between two teams because there is more of it. Post the color key on the board.
17. Tell students that each team will plot their data points on a small world map, (World Map (PDF)), using the assigned color. Later each team will add their data to the class world map. Demonstrate how to plot a data point.
18. Have teams transfer their data to a large world map using colored push pins that match the colored pencils. (Note: This process may take twenty to thirty minutes.) Have students check off the fossils on their data sheets as each pin is placed, to prevent repeats.
19. Tell students to return to their teams to analyze the distribution of fossils on the world map and answer theHominid Migration Discussion Questions (PDF). Have teams discuss their answers.
20. Ask students to refer to the class map as they think about the following questions:
- Which human species overlap in time and, possibly, place?
- What biological adaptations would you expect to find in modern human populations in different parts of the world?