Activity: Brain Size vs. Bipedalism (Part B)

Cranial Measurements: Determine whether the relative brain size of A. afarensis was more similar to modern humans or modern chimpanzees. (Remember that the primitive condition is expected to be more like that of a modern chimpanzee).

In this section of the activity, you will take 3 measurements: cranial width (the widest part of the skull), cranial length (the distance from the forehead just behind the eyebrows to the bac of the skull), and cranial height (the distance from the top of the cranium to just below the ear).  Use the images in the chart as a guide.

  1. There are 2 options for the skull measurements. If your school has access to casts of a chimpanzee, a modern human, and an australopithecine skull, use digital calipers to measure in cm the width, length, and height of each cranium. Or you can use the images provided in this lesson. Estimate the cranial width, length, and height using the scale provided in the top right corner of the images.  Create or print out the graph below and record your results in the appropriate spaces.
  2. Calculate the cranial volume for the three specimens by multiplying the cranial width, cranial length, and cranial height by 1.333 x 3.14, then divide your answer by 10.   

  4. Answer the following question based on your results:

      -Was the brain size of A. afarensis more similar to modern humans or modern

Cranial Images