Australopith and Early Homo Locomotion

Groups: Your Color groups

Purpose

There are many ways we can study the bones of animals (whether fossilized or not) to understand their way of life. For early human ancestors, the shape of the leg and arm bones can be used to determine their type of locomotion. Anthropologists often take a variety of measurements on bone, as well, to compare between different specimens or different species. In this exercise, we will use one of the simplest of these measurements, the Humerofemoral Index.

The Humerofemoral Index is simply the maximum length of humerus/maximum length of femur x 100. The result tells you how long the major muscle-bearing bone of the arm is, relative to the major muscle-bearing bone of the leg. If the index length is less than one hundred, then the femur is longer than the humerus. This suggests that powerful legs are more important than powerful arms for that particular species. This is common in animals that leap or walk. On the other hand, if the index length is higher than one hundred, then the arms were more powerful than the legs. This is common in animals that brachiate.

How do humans compare to other primates?

Goals

• • To introduce one way that anthropologists study fossils and the bones of living animals

  • To reinforce the idea of cross-species comparisons when studying fossils

  • To illustrate the differences in locomotion between different human ancestors

Procedure

• 1. Within your color group, compare birth dates. Divide into roles based on your age, as follows:

     1. 1. Oldest member of group: recorder The recorder will take notes on the group's discussion. If anything needs to be turned in, the recorder will do so.

        2. Second-oldest member: time-keeper The time-keeper makes sure the group stays focused on the activity and completes the steps on time.

        3. Second-youngest member: presenter The presenter will speak for the group during the whole class discussion.

        4. Youngest member: leader The leader makes sure every voice is heard, and helps encourage the group to stay on-task

  2. The recorder should write each person's full name on the handout.

  3. You will be given a handout with information about the humerus and femur length of various primates, living and extinct. Calculate the Humerofemoral Index, as shown. This should take no more than 5 minutes.

  4. There are three questions on the back of your handout. Take 5-10 minutes to answer the questions as thoroughly as possible.

  5. Presenters should be ready to talk about their answers with the whole group

Take-home Messages:

• • Even though we can't see living specimens of our ancestors, we can use comparisons to other living species to understand the meaning of their physical traits

  • Humans have a unique type of locomotion among primates, but our earlier ancestors were unique from both chimpanzees and us.

Reflection

Take five minutes to reflect on the activity. How does this activity illustrate the methods anthropologists use to understand our ancestors? If you found this activity particularly helpful or not helpful, please tell me why.