In this activity, students observe and interpret "fossil footprint" evidence. From the evidence, they are asked to construct defensible hypotheses or explanations for events that took place in the geological past. The estimated time requirement for this activity is two class periods. This activity is designed for grades 5 through 8. The activity is adapted with permission from the Earth Science Curriculum Project.11
This activity provides all students an opportunity to develop the abilities of scientific inquiry and understanding of the nature of science as described in the National Science Education Standards. Specifically, it enables them to:
propose explanations and make predictions based on evidence,
recognize and analyze alternative explanations and predictions,
understand that scientific explanations are subject to change as new evidence becomes available,
understand that scientific explanations must meet certain criteria. First and foremost, they must be consistent with experimental and observational evidence about nature, and must make accurate predictions, when appropriate, about systems being studied. They should also be logical, respect the rules of evidence, be open to criticism, report methods and procedures, and make knowledge public. Explanations of how the natural world changes based on myths, personal beliefs, religious values, mystical inspiration, superstition, or authority may be personally useful and socially relevant, but they are not scientific.
This activity provides teachers with the opportunity to help students realize the differences between observations and inferences. In terms of the Standards, it centers on the development of explanations based on evidence. It encourages students to think critically about the inferences they make and about the logical relationships between cause and effect.
Observations or statements of observations should have agreement by all individuals: "These are fossil footprints," or "The dimensions of one of the footprints is 20 cm by 50 cm." Inferences are statements that propose possible explanations for observations: "The two sets of footprints represent a fight between the animals." If this is true, then what evidence could you look for to support the inference. Note that the primary emphasis for this activity is developing abilities and understandings for ''Science as Inquiry" as described in the Standards.12
Make an overhead transparency of the footprint puzzle from the master provided on page 89. Have a blank piece of paper on hand to mask the puzzle when it is put on the projector.
Engage Project position 1 of the footprints from the overhead by covering the other two positions with a blank piece of paper. Tell the students that tracks like these are common in parts of New England and in the southwestern United States. Point out to the students that they will be attempting to reconstruct happenings from the geological past by analyzing a set of fossilized tracks. Their problem is similar to that of a detective. They are to form defensible explanations of past events from limited evidence. As more evidence becomes available, their hypotheses must be modified or abandoned. The only clues are the footprints themselves. Ask the students: Can you tell anything about the size or nature of the organisms? Were all the tracks made at the same time? How many animals were involved? Can you reconstruct a series of events represented by this set of fossil tracks?