Gene Drift Model Information
WHAT IS IT?
This model is an example of random selection. It shows that turtles that randomly exchange colors converge on a single color. The idea, explained in more detail in Dennett's "Darwin's Dangerous Idea", is that trait drifts can occur without any particular purpose or "selective pressure".
HOW DOES IT WORK?
The model starts with a random distribution of colored turtles. They move by wiggling randomly across the world. Each turn, a turtle produces between 0 and 4 offspring. If the total number of turtles is greater than the original number, then turtles are randomly killed until the original number is restored. After enough turns, a color will gain a slight dominance. By statistical advantage, a dominant color becomes more likely to win the entire grid. However, because the process is random, there will usually be a series of dominant colors before one color finally wins. Equally important is the fact that a color can never come back once it dies out.
HOW TO DO I USE IT?
THINGS TO NOTICE AND TO TRY
Gradually a color will gain a slight dominance. By statistical advantage, a dominant color becomes more likely to have more colors like it. However, because the process is random, there will usually be a series of dominant colors before one color finally wins.
CREDITS AND REFERENCES
To refer to this model in academic publications, please use: Wilensky, U. (1997). NetLogo GenDrift T reproduce model. http://ccl.northwestern.edu/netlogo/models/GenDriftTreproduce. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
In other publications, please use: Copyright 1997 Uri Wilensky. All rights reserved. See http://ccl.northwestern.edu/netlogo/models/GenDriftTreproduce for terms of use.