Using the inference that all life is descended with modification from common ancestors, students calculate approximate "cousinhood" relationships between humans and non-human primates and several other organisms. Using human pedigrees as a model for descendant-ancestor relationships spanning a few generations, students can then extrapolate to time periods spanning several thousands or millions of generations.

All species of living things currently on the Earth are related on a genealogical level called "cousins," related to, but not descended from each other.

ASSESSABLE OBJECTIVES

Students will...

1. recognize that all organisms must possess ancestors, though not all leave descendants.
2. determine numerically that most relationships among living things are best defined as "cousins," whereas only a few relationships are best defined as ancestor-descendant.
3. recognize the similarities between small scale genealogies like human family pedigrees and evolutionary phylogenies.
4. associate degrees of similarity with relative timing of evolutionary distance.

TEACHING STRATEGY & PREPARATION

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

1. Following the completion of a unit on genetics.
2. Integrated into a general science, earth science or biology lesson that looks at the fossil record and examines the relationships among fossil specimens and modern day organisms.
3. As part of a unit on human biology, inheritance, and genealogy where students gain experience with information regarding the construction of pedigrees and their use.
4. Following a unit on taxonomy, classification and evolution, where students have surveyed the characteristics of living things and may want to explore more deeply the evolutionary insights that emerge from these concepts.

Preparation

1. Provide handout materials for each team of students:
   - Stapled set of the 6-page Student Activity Packet for each student
   - Graphics page featuring Figures 3 and 4 for each student
   - 2-sided Calculating Cousins Summary Page for each student
2. Prepare teacher materials for Recommended and/or Optional Extension Review:
   - photocopy to card stock and cut out card sets A and B. Place in 2 separate containers, one marked A and the other marked B.
   - scotch tape
   - overhead of blank phylogeny and teacher key phylogeny
   - overhead projector and chalk for chalkboard OR dry erase markers for whiteboard.

1. Open the activity with a catchy phrase like "Well I'll be a monkey's uncle" and ask students if there is any truth in that statement. Or, you might want to find a composite picture from a zoo information booklet and place the title "Family portrait" prominently beneath it and see what kind of response you get from students. In each of these circumstances it might be useful to see if students express any of the common misconceptions that this activity attempts to address.

2. For best results, teams of 4 students should work together. Teams of 4 are recommended for cross-checking of calculations or to more effectively divide up the assigned tasks. They should then pick the 5 of the 11 possible cousin calculations they will be completing. Have the students or student teams report to the teacher which ones they are doing so that , if necessary, the teacher can reassign calculations so that each one of the eleven calculations will be covered by the class. Each student does the 5 different calculations. Note that in each of the three categories from Section 3, only a portion of the sample needs to be completed: three from Part A, one from Part B, and one from Part C. Remind students not to write on the Student Activity Packet.

3. As the student teams complete their five calculations, students should be checking their work with lab team members, and answer all self-check and activity questions. Students should not begin writing the summary essay until the end of the lab, perhaps as a homework assignment. Each student is responsible for completing and turning in a Calculating Cousins Summary page.

Recommended Review: presenting results and building a phylogenetic tree

4. When the class appears finished, the teacher surveys the student groups to see which groups have done which calculations, noting especially any calculation done by only one group. This group would therefore be required to present that piece of information to the class since no other student team had done it. Hand out to student teams pieces of the card set A with names of the creatures studied in this exercise. Each group should get at least one card.

5. Next, the teacher uses the overhead of the blank phylogeny chart (taped to the overhead projector to prevent movement). It is recommended that the teacher trace the lines projected on the board with chalk or dry erase marker so that the overhead can then be turned off and students can work in a lighted classroom. The teacher should write in the "nodes" A-J and announce to the students that these points represent divergence points from common ancestors. Students will discuss this later in the review.

6. The teacher then hangs each card of set B ("cousinth relationship, times removed") on the board for students to see, using tape (or magnets on magnetic board).

7. The teacher then announces the placement of each of the set A name cards, in the same order as they appeared in the student activity pages. Students come up, one at a time, and place their name card on the right side of the phylogeny, in line with the name "human" already typed in on the chart. After each student places their name card on the phylogeny, they then select one of the B set cards (with "cousinth, times removed") hanging on the board and then position the B set card to the right of the A set card. During this process the teacher can help guide a conversation about how close common ancestry is often shown in the large number of similarities between two creatures, whereas distant common ancestry usually results in creatures with fewer anatomical similarities. You may want to include the Australopithecine "Lucy" in the conversation once all other Set A and Set B cards have been placed. Some scientists consider Lucy to be one of the direct ancestors of modern humans, while others consider the specimen to be a very, very close cousin.

8. Complete the class review by talking about the branching points A-J on the chart. Discuss how, for example, two creatures like a snapping turtle and bullfrog could have the same branching point from a common ancestor as a bullfrog and a human, even though bullfrogs seem to have more in common with the snapping turtle.

Optional extended review: (the teacher can suggest these as possible additional assignments to be completed in class or at home)

1. If the students have done well with the recommended review, challenge them to create a phylogenetic tree that is entirely scaled on the horizontal axis. Dotted horizontal lines on the phylogeny were an indication that the scale of 1 mm = 2 million years could not work because the lines would have gone off the chart. What is the scale now when projected on to the board? Encourage students to erase and redraw the dotted horizontal lines so that they are to scale. (Correctly scaled, the horizontal axis with redrawn branching points may go off the board. )

2. Have students create a family tree for their family going back to their great-grandparents. Use appropriate symbols and label each individual with full name, birth date, marriage date (if any), and date of death if deceased. Be mindful of the fact that many students may not be the biological descendants of their parents. In such cases, have equivalent/alternative activity opportunity for those students, e.g., doing a friend's family, or tracing three or more generations of a famous person's family (the JF Kennedy family, the Kirk Douglas family, etc.)

3. Have students create an expanded family tree, a phylogeny, for themselves and other organisms in the school lab or in their household. Consider fish in a fish tank, small rodents, dogs or cats, pet iguanas, etc. Label this phylogeny with each creature's name and approximate "cousinth" relationship with them based on this activity.

4. Given their ethnic heritage, have students infer where their ancestors were and what they did 10,000 years ago. Have students illustrate with drawings showing them actively engaged in a daily activity appropriate to the area. Include clothing, utensils, food acquisition implements and techniques, housing structures; anything that is appropriate. Students can assist their search by accessing information on-line. Then have students draw their descendants 10,000 years in the future. Have students comment on/illustrate what they will be like, how they will live, what transportation will be like, what they will wear, and/or what structures they will live and work in. Put these 2 drawings side by side and have students create a list that includes 5 things that remain the same and 5 things that are different between their ancestors of 10,000 years ago and possible descendants 10,000 years in the future.

5. Have students extend their current family tree from #2 above by fancifully predicting their future relatives. Attach a piece of paper to the bottom of the pedigree completed in #2 above and draw in 3 more generations of individuals. Have students speculate on names of future spouses, number of future children and their spouses, etc. , grandchildren, great grandchildren and their birth dates, etc. until they have an expanded family tree with them as one of the great grandparents somewhere in the middle of this growing family tree.

ASSESSMENT

Examine student or student team work on the Calculating Cousins Summary Page. 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 concept. Check team understanding of the material by looking at the placement of the A and B cards by each team.

Two excellent and conceptually consistent follow-up lessons which use several of the same creatures explored in this activity:

1. "Making Cladograms: Phylogeny, Evolution, and Comparative Anatomy"
   Relative divergences from common ancestors for a similar group of vertebrates determined using cladistics.
   http://www.indiana.edu/~ensiweb/
   lessons/mclad.html
2. "Molecular Biology and Phylogeny"
   Molecular evidence from cytochrome c amino acid sequences to determine relative divergences from common ancestors.
   http://www.indiana.edu/~ensiweb/
   lessons/mol.bio.html

ENSIweb is an online resource (from the Evolution and the Nature of Science Institutes) which provides detailed classroom-tested lesson plans with reproducible handouts and expected outcomes. Evolution and the Nature of Science Institutes ( http://www.indiana.edu/~ensiweb/home.html)

Bibliography

Glick, Joe. 1995 . Harrisonburg High School. Harrisonburg, VA "Time Conceptualization." Classroom Activity

Campbell, Bernard. 1982. Humankind Emerging. Little, Brown and Co, Inc. Boston. Chapter 5, pp 93-117.

Colbert, Edwin H. 1969. Evolution of the Vertebrates: A History of Backboned Animals Through Time. Second edition. John Wiley and Sons, Inc. New York.

Strahler, Arthur. 1987. Science and Earth History - - The Evolution/Creation Controversy. Prometheus Books. Buffalo, N.Y. pp 312-313.

Strickberger, Monroe. 1990. Evolution. Jones and Bartlett Publishers, Boston. Chapters 18, 19.

Jones, Steve & Robert Martin and David Pilbeam, editors. 1996. Cambridge Encyclopedia of Human Evolution. Cambridge University Press. Bristol, Great Britain.

National Academy of Sciences. 1998. Teaching About Evolution and the Nature of Science. Activity 4 - "Investigating Common Descent: Formulating Explanations and Models," pp81-83. National Academy Press,. Washington , DC.

Klein, Richard G. 1999. The Human Career. University of Chicago Press. Chicago, IL.