How Tall Were They? Footprints activity
Adapted from "Footsteps in Time" © 1999 ENSI (Evolution & the
Nature of Science Institutes) www.indiana.edu/~ensiweb
This material may be copied only for noncommercial classroom teaching purposes, and only if this source is clearly cited.
"One of the most remarkable events in the annals of anthropology occurred (over) 20 years ago in an area of northern Tanzania called Laetoli. A team lead by famed archaeologist Mary D. Leakey was searching for fossils of early hominids that ranged through East Africa millions of years ago. In the summer of 1976, after a long day in the field, three visitors to Leakey's camp engaged in some horseplay tossing chucks of dried elephant dung ant one another. When paleontologist Andrew Hill dropped to the ground to avoid being hit, he noticed what seemed to be animal tracks in a layer of exposed tuff- a sedimentary rock created by deposits of volcanic ash. On closer inspection of the area, the scientists found thousands of fossilized tracks, including the footprints of elephants giraffes, rhinoceroses, and several extinct mammal species. But the most extraordinary find came two years later, when Paul I. Abell, a geochemist who had joined Leakey's team found what appeared to be a human footprint at the edge of a gully eroded by the Ngarusi River. excavations of the Footprint Tuff, as it came to be known, in 1978 and 1979 revealed two parallel trails of hominid footprints extending some 27 meters (89 feet). the volcanic sediments were dated radiometrically to be between 3.4 million and 3.8 million years old." (Agnew, Neville and Demas. Scientific American. :Preserving the Laetoli Footprints." September 1998. P. 45-66.)
Objective: How do we determine the height of hominids based on foot length?
1. Look at the Northern and Southern sections of the Laetoli trackway. Create a hypothesis (in your journal) about who could have left those footprints. Be as descriptive as possible (i.e. what type of organism make the footprints, what were they doing, and how old are these organisms?)
2. Inspect the G1-27 and G1-33 footprints. How could you determine the height of these organisms? How could you determine how the footprints were made? (Did you notice that one of the footprints is actually a left foot, check out the southern portion of the trackway?)
3. In order to answer the previous two questions, develop a hypothesis and procedure to test your hypothesis in class, then:
a) measure each footprint, using your lengthy relationship data, determine the height of the person.
b) measure the stride distance for the G1 person on the trackway, take several measurements and determine the mean, then convert the mean from the scaled down trackway to the actual stride distance using the scale information on the trackway. Determine your height from the lengthy relationship graph you made earlier. (Note 44.5 mm of trackway is equal to 1 meter actual distance; take the scale measurement divide by 44.5 and the value will be a decimal which multiplied by 100 is in cm).
c) measure the plaster cast footprints of the female and male students (use the walking plaster cast); determine your height from the lengthy relationship graph you made earlier.
d) make a sand print of your footprint in the moist sand in the classroom, measure your footprint in cm and determine your height from the lengthy relationship graph you made earlier.
4. Create a data table for your experiment and record class data (in centimeters).
5. NOTE: the actual height of the male plaster cast footprint is 6' 6", the female is 5' 2" (convert the height to inches and then multiple by 2.54 to convert to cm). The actual height of A. afarensis is between 1.0 -1.3 meters. (remember that 100 cm = 1 meter).
Post Lab Questions:
1 Determine the percent error for the plaster cast height (get correct height from teacher). Use the formula below; (the absolute value of the actual height minus the estimated height divided by the actual height, then multiply by 100). Remember the actual heights are listed in procedure #5 and the estimated height is determined by using the graphs made in the lengthy relationship activity.
|actual height-estimated height| / actual height x 100 = % error
2. Taking into consideration the % error above, calculate the height range for the organism that made the G1-27 and G1-33 footprints.
3. What factors could have influenced the quality of the footprints?
4. Write a short story describing how the footprints were originally made? Include any information that you know about the area and time period. Be creative, make a comic strip, poem, jingle, etc.