Teachers Notes s1

Teachers Notes

·  This experiment is adapted from ENSI webpage (http://www.indiana.edu/~ensiweb/lessons/footstep.html). The site contains a lot of different ways to do this experiment.

·  I had the original tracks printed up to actual size, so the students could walk on it. I would highly recommend it (I got a real thrill walking on it!). The ENSI site will send you the orginal to expand (they sent all the way to China for me!)

·  Read “Preserving the Laetoli Footprints, (Agnew, Neville, and Martha Demas. "Preserving the Laetoli Footprints". Scientific American, Sept. 1998, pp.44-55.). Gives an idea of the importance of the Laetoli Footprints. I would recommend giving it to older students to read.

·  The original nature article also has measurements of the footprints. Average size

Trail 1: length/breadth 18.5cm X 8.8cm

Average stride length: 38.7 cm

Trail 2: length/breadth 21.5cm X 10 cm

Average stride length: 47.2 cm

·  A related article of human footprints found in the relatively same area (Wilandra lakes document) could also be used for a comparison.

·  From the previous experiment, the following information can be determined:

foot length

leg length

height

stride length running

stride length walking

·  Other information that you can “guide” the students to:

Stride length changes. Any ideas why? Stopping to look around? something scared them? Were they walking or running?

One set of footsteps (the larger track) looks different (research suggests that another hominid walked in the footsteps of the larger hominid for a total of 3 hominids.) What other reasons? (Some research has suggested that the larger foot slipped more in the mud)

Have two students walk the footsteps together (works best is someone large and small). What you will find is that the students have to be very close to each other. What other arrangements could be used to explain the footsteps ?

The large set of footprints suggests that the hominid was 5 feet tall (1.524 m), the hominid walking in the footsteps of the larger was 4.5 feet tall (1.37 m), the smaller set of footprints was 4 feet tall (1.22 m).

The sizes suggest two males (one older and one younger) and one female. What does this say about sexual dimorphism in the hominid?

Based on your data, what hominid might this be?

·  Students will need to refer back to their previous experiments. A lot of that is baseline data they can use.

·  The other research papers can be given to compare the students data.

·  Even if we can't have absolute certainty about the identity of the trackmakers of Laetoli at present, the tracks themselves can tell us much about the functional morphology of the creatures that walked through the volcanic ash. While the tracks are very small, the two more easily distinguishable prints being between 18 and 22 cm long, they show some remarkable characteristics that prove that the hominids were walking upright on two legs. First, there are no impressions of knuckles on the ground, indicating that these animals were not moving in the manner of modern day Chimpanzees, Gorillas, or Bonobos. More importantly, however, the big toe is brought in line with the rest of the toes at the front of the foot and does not jut out to the side as in extant great apes. The condition of the toe is not as derived as in humans or later bipedal hominids, but the difference between the Laetoli foot structure and the foot structure of living apes is remarkable. The footprints are not simply flat impressions, either; they can tell us a bit about how these animals walked. They did not shuffle or stop, but rather walked by placing the heel down and then pushing off with the front of the foot and toes (hence the move of the big toe), again proving that the tracks were made by creatures walking on two feet. Indeed, hominids were upright, obligate bipeds by 3.5 million years ago at the latest, but what sort of world did the "upright apes" inhabit? (extracted from Laelaps, Brian Switek)

·  Laetoli Footrprints (measured from the G1 and G2 footprints)

from Tuttle [1987]: G1: 180.4 +/- 4.8 mm; G2: 208.8 +/- 11.6 mm

(David A. Raichlen et al., The Laetoli footprints and early hominin locomotor kinematics, J Hum Evol (2007), doi:10.1016/j.jhevol.2007.07.005)

·  The original nature article also has measurements of the footprints. Average size

Trail 1: length/breadth 18.5cm X 8.8cm

Average stride length: 38.7 cm

Trail 2: length/breadth 21.5cm X 10 cm

Average stride length: 47.2 cm

(Leaky, M.D, and R.L Hay. " Pliocene footprints in the Laetolil Beds at Laetoli, northern Tanzania." Nature 278 (1979): 317-323.)

·  The Becoming Human Website (www.becominghuman.org) has information about height and so forth. (under lineages and profiles)