December 22, 2008

Primate Bipedalism: Understanding Standing Up

Becoming Human is an interactive documentary experience that tells the story of our origins.
Journey through four million years of human evolution with your guide, Donald Johanson.

For this experience you will need to:

Anthropologists and evolutionary biologists agree that upright posture and the subsequent ability to walk on two legs was a crucial major adaptation associated with the divergence of the human lineage from a common ancestor with the African apes. Efficient upright walking required numerous changes in the anatomy of the limbs and pelvis and we are the result of the variations and selection pressures that forged this new ability. The ability to walk on two legs was later followed by other human evolutionary trends that lead to tool manufacture and the enlargement of the brain.

Main Concepts

Human evolution is marked by a mosaic pattern. This means that different parts of the body, and different adaptations, evolved at different times and different rates. The anatomical changes associated with bipedalism emerged as among the earliest innovations of the human lineage.

Assessible Objectives

Students will...

  1. identify key anatomical similarities and differences between the great apes and humans.
  2. infer likely anatomical features in ancient human ancestors.
  3. list principal anatomical changes in primates necessary for adaptation to fully bipedal locomotion.
  4. sequence particular anatomical features in hominids as part of a series of broader evolutionary trends.

Teaching Strategy & Preparation

This activity can be effectively and easily inserted into any one of several parts of your course. For example:

  1. As part of your evolution unit in which comparisons between chimpanzee and human characteristics leads to an analysis of essential differences in locomotor pattern and cranial capacity.
  2. As part of your unit on human anatomy and physiology where the focus of the lessons would be the skeletal and muscular systems and how they are adapted for bipedal locomotion.
  3. As part of a unit on animal behavior which looks at migration and culminates with an examination of human dispersal around the planet from a region of origin in Africa.

Students may work independently, but will benefit most from the dialogue among partners when working in groups of two or three.


For each pair of students...

  1. Photocopy the image pages of chimpanzee, human and australopithecine to overhead transparency film. The australopithecine template has letters on the template that can spell out "IM LUCY" . The human template can spell out "WALKER" and the chimpanzee can spell out "PONGID." Cut the 12 images of the chimp and human anatomy and place in an envelope marked "Part 1" . Cut the written clues for Part #1 and also place in this envelope, or you may want to read the clues at random to your students and have them place the anatomy pieces based on your reading. Place 2 large paper clips in this envelope.
  2. Cut the six images for the australopithecine and place in an envelope labeled "Part 3." Place the Part #3 clues in the envelope. Place one large paperclip in this envelope.
  3. Print out the Primate Reconstruction Page on plain or colored paper in "landscape" mode. Photocopy the "Reconstructions" page, but do not staple it to the set of other student materials.
  4. Photocopy and staple the 6 page Student Activity Packet.
  5. Have paper towels and a water source handy for Part 2 which involves creating a hominid trackway.
  6. Provide a water-based overhead marking pen.
  7. Set up a small tray or box from which students may take additional paperclips if necessary.


  1. You might want to open up the discussion by asking students about their favorite animal or an animal that they find interesting. Inevitably, primates such as chimpanzees come to mind and you can probe students. interests in this creature. More often than not, students will say that they seem so humanlike.
  2. Follow that conversation briefly with a discussion about so-called "missing links" and what is properly meant by this phrase. (Realistically, NOT any direct ancestor species, but rather a collection of closely related species, "cousins", with intermediate traits, which lived and went extinct during the evolutionary history of a group.) Have students briefly comment on what kinds of physical features would be considered intermediate. You might also briefly explore what students know about the current status of fossil discoveries documenting the evolution of hominids.
  3. Proceed to distribute materials to each pair of students. Have students record any written answers or responses on a separate sheet of lined notebook paper. Keep in mind that students are sorting anatomical pieces like arms, legs, pelvis, skull, thorax, etc. as overlays on a traced border of each organism on the "Reconstructions" page. Remember that you can choose to read the clues instead of including the clues in the student envelopes.
  4. Check with each student pair after they complete Part 1, using the teacher answer pages to determine if students have properly used their clues for precise ordered placement of the pieces. If a piece is misplaced or not in the correct order, ask students to make needed corrections, preferably without telling them specifically what is wrong. They can figure it out by reviewing the clues and checking the order of the placed pieces. Check student responses to discussion questions as well.
  5. Students should be allowed to go to Part 2 only after successfully completing Part 1. Carefully monitor the creation of their own hominid trackway. This does seem to work best on dry concrete. Check student responses to the questions in Part 2, OR save the review of these questions for a lively review at the end of class.
  6. In Part 3 monitor the placement of the final six pieces representing an australopithecine and check for proper ordering of the pieces. Use the teacher answer pages to determine if students have properly used their clues for precise ordered placement of the pieces.


Use some or all of the Check Questions, along with a few additional questions in a quiz to see if students fully grasp the main concepts. The questions in part 2 end up being a source of lively discussion as a class if you prefer not to review the answers with each paired team prior to letting them move on to Part 3 of the exercise. Be sure to test for the stated Assessment Objectives. Here are some examples:

  1. Given either pictures or descriptions of skeletal features of hominids, including modern human, apes and australopithecines, students will assign them to their appropriate group.
  2. Given sample questions from this lesson regarding timing of first appearance of selected traits, including those associated with bipedalism, students will answer correctly in terms of the relative timing of those features, creating a mosaic as opposed to a sudden appearance of fully human traits.

Extensions & Variations

  • Students could test their skill by mixing all pieces together and sorting them, again with the clues, as a final test of understanding. Or if they are an advanced group you might just go ahead and mix ALL of the 18 acetate pieces together to see if they can use both sets of 6 clues to reassemble the 3 skeletons simultaneously.
  • Have students research several hypotheses on the factors that may have contributed to the evolution of bipedalism. Let students research one or several factors and select the one that is most highly regarded by the scientific community and explain why it is currently the consensus view.
  • Create a timeline of 10 important events or discoveries in paleoanthropology. Discuss the prevailing views of the time and how each of these new discoveries or conclusions lead to a dramatic change in how scientists later viewed human evolution.
  • Go to the zoo to observe primates. Record observations for later discussion that address significant similarities and differences between humans and the great apes in their mode of locomotion.
  • Have students create an animated flip-card book illustrating either human locomotion (p. 75 Cambridge Encyclopedia of Human Evolution) or chimp locomotion (p. 395 Strickberger) If necessary have students complete the animated sequence if the images shown do not include the entire pattern of locomotion.
  • Have students read and discuss the Scientific American article If Humans Were Built to Last and share any additional design flaws they may be aware of. Have them talk to a local doctor about anatomical or physiological flaws and present their findings to class in order to compile a class list for group discussion.

Some excellent and conceptually consistent follow-up lessons to this activity:

  1. "Hominid Chronology"
    Students infer a likely pattern of dissent among numerous fossil hominids present in the fossil record by plotting chronological distribution. From ENSIweb.
  2. "Hominid Cranial Comparison"
    Student quantitative measurement of actual replicas of extinct and extant hominoid crania encourages evaluation of humanlike characters of fossil intermediates. From ENSIweb.
  3. "Footprints in Time: Analysis of the Laetoli Footprints"
    Inferring stride length, total height and walking speed in early australopithecines using student modeled walking data. From ENSIweb. Or see the "Watch Your Step" activity in the WGBH/PBS-Evolution Teacher's Guide, page 24.
  4. "Investigating Common Descent"
    In this activity, students formulate explanations and models that simulate structural and biochemical data as they investigate the misconception that humans evolved from apes. Grades 9 through 12.
  5. "Fossils and Migration Patterns of Early Hominids"
    Type and location of abundant hominid fossil data is plotted on a world map to determine a continent of origin and a likely path of dispersal throughout the world. Also, see the version in the WGBH/PBS-Evolution Teacher's Guide, page 25.
  6. "The Chromosome Connection"
    An activity on this IHO Web site. Also see variation: "Comparison of Hominoid Chromosomes" (especially the part in which the chromosome banding patterns are compared between humans and the three great apes.): , and another version, "Chromosome Clues", in the WGBH/PBS-Evolution Teacher's Guide, page 24.
  7. "Molecular Sequences & Primate Evolution"
    Beta hemoglobins from several different primates (including apes and humans) are compared, leading to the building of a cladogram, and a consideration of how these data can form the basis for a molecular clock:

References & Resources

ENSIweb is an online resource (from the Evolution and Nature of Science Institutes) which provides detailed classroom-tested lesson plans with reproducible handouts and expected outcomes. Evolution and the Nature of Science Institutes (


  • Campbell, Bernard G., 1982. Humankind Emerging. 3rd edition. Little, Brown and Company, Boston. Pp. 213-222.
  • Jones, Steve & Robert Martin and David Pilbeam, editors. 1996. Cambridge Encyclopedia of Human Evolution. Cambridge University Press. Bristol, Great Britain. Sections 2.8-2.9 Pages 75-81.
  • Klein, Richard G. 1999. The Human Career. University of Chicago Press. Pages 66, 208-209.
  • Lewin, Roger (1), 16 September 1988. "Hip Joints: Clues to Bipedalism." Science. Volume 241. Pp. 1433.
  • Lewin, Roger (2), 1988. In The Age of Mankind. Smithsonian Press.pp. 50-68.
  • National Academy of Sciences. 1998. Teaching About Evolution and the Nature of Science. National Academy Press,. Washington, DC.
  • Nelson, Harry and Robert Jurmain. 1991. Introduction to Physical Anthropology. 5th edition. West Publishing, Inc. St. Paul, MN. pp. 428-435.
  • Olshansky, S. Jay, Carnes, Bruce A., and Butler, Robert N, March 2001. "If Humans Were Built to Last" Scientific American. pp. 50-55
  • Strahler, Arthur. 1987. Science and Earth History - The Evolution/Creation Controversy. Prometheus Books. Buffalo, N.Y.
  • Strickberger, Monroe. 1990. Evolution. Jones and Bartlett Publishers, Boston. Pp. 392-395.
  • Tattersall, Ian et al, editors. 2000. Encyclopedia of Human Evolution and Prehistory. Garland Publishing. New York. Pages 394-395.
  • Zihlman, Adrienne, 1982, 2000. The Human Evolution Coloring Book. Coloring Concepts, Inc. Oakville, CA

Time Required

This activity can be easily completed in one 45 minute period.


  1. Student Overview
  2. Reconstructions Page
  3. Human Anatomy
  4. Chimpanzee Anatomy
  5. Australopithecine Anatomy
  6. Student Clues Page
  7. Student Activity Packet
  8. Teacher Answer Pages
  9. Envelopes: 2 for each pair of students
  10. Paper Clips
  11. Paper Towels
  12. Water Source
  13. Water-based Overhead Marking Pen

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