Clines and Population Variation
Groups: Your Number group
Purpose
Anthropologist Frank Livingstone wrote, in 1962, "There are no races, only clines." In this activity, we'll explore what he meant by considering the clinal distribution of human diversity around the world.
Goals
To introduce and provide practice with the concept of clinal distributions
To explain the difference between concordant and discordant variation, and how this relates to human biodiversity
To reinforce the concept of human biodiversity as continuous, while racial categories are arbitrary and categorical
Further practice with the scientific method of data gathering, description, and analysis
Procedure
Divide into your number groups. Choose your roles based on your shoe size, as follows:
smallest shoe size: recorder The recorder will take notes on the group's discussion. If anything needs to be turned in, the recorder will take care of it.
second smallest shoe size: time-keeper The time-keeper makes sure the group stays focused on the activity and completes the steps on time.
second largest shoe size: presenter The presenter will speak for the group during the whole class discussion.
largest shoe size: leader The leader makes sure every voice is heard, and helps encourage the group to stay on-task
Each group member should write their own name on the top of the handout.
A cline is a gradual, continuous change in a particular trait or trait frequency over space. A clinal map
looks like a topography map, with lines representing changes in the trait or frequency. At the right is an example of a clinal map, showing the frequency of yellow-brown hair within Australian Aboriginal communities.Using the information given to you on your handout, each person should create their own clinal map for the trait they were assigned. You will not have enough data to make an extremely detailed clinal map, but do your best to fit the patterns described by the handout. I recommend that you use a pencil to create the initial map, then use the crayons or markers provided to shade in the different clines. Make sure you include a title and legend so others can interpret your map
When you are finished with your map, describe the distribution of your trait with the rest of your group. Can you create one or more hypothesis as to why your trait follows this specific distribution? What data would you need to test this hypothesis? If we have time, we will share some of these hypotheses with the whole class.
When all maps have been finished, compare the distribution of the four different traits (or three, if you have fewer people in your group). Answer the following questions:
Are the clinal maps all the same? That is, does the distribution of one trait follow the same distribution as the other traits? Why or why not?
How do these clinal maps illustrate that race is not a biological reality, but a cultural construct?
As a class, we will discuss the concepts of concordant (dependent, or tracking) and discordant (independent or non-tracking) variation.
Take-home Messages:
Human biodiversity is clinal, discordant, and continuous, but racial labels are categorical. Therefore, "race" does not reflect biological reality.
Reflection
Please put your reflection on the back of your map. You may reflect on any aspect of this activity that you choose, but if you would like some questions to help you start: What was the most important thing you learned in today's class? What questions do you still have about these topics?
