Introduction to Evolvulator
Welcome to Evolvulator! These web pages are designed to illustrate some of the basic concepts of population and evolutionary genetics. They use simulations to show the effect of evolutionary processes—mutation, random drift, selection, migration, and recombination—on genetic variation within and between populations.
Mutation, drift, migration and recombination are processes that involve chance events. Whether or not a particular gamete carries a new mutation, for example, may depend on whether a cosmic ray that originated in an exploding supernova millions of light years away happens to hit a strand of DNA at just the right place. Most of these simulations, therefore, are Monte Carlo simulations, meaning they use random numbers to model these random processes. (Technically, they're pseudorandom numbers, but they're random enough for our purposes. The roulette wheels of Monte Carlo that these simulations get their name from technically aren't random, either, they're just unpredictable.) For example, here's a very simple simulation of mutation in 10 haploid individuals. The mutation rate is 0.1 mutations per individual per generation. This means that on average, one-tenth of the individuals will experience a new mutation (indicated by a solid blue square).
One generation of mutation
Natural selection is not a random process, so some of the simulations are deterministic; they model a situation in which the result is always the same. For example, if the frequency of the blue allele is 0.1 and it has a relative fitness of 0.89, its frequency in the next generation will always be 0.09 in a deterministic model. This is a pretty unrealistic model, because random drift is always occurring, so most of the simulations of selection are Monte Carlo simulations that include both selection and drift.
The graphs in Evolvulator are drawn using the <canvas> element of HTML. This is only supported by modern browsers; it works best with Firefox, and it should work to some extent with Safari, Opera, Chrome, and iCab. Microsoft has, for some reason, decided they don't want to use the <canvas> element, so these pages won't work with Internet Explorer.
In Firefox, you may get an error message that says "Warning: Unresponsive Script." If so, click the box labelled "Don't ask me again" and then hit the "Continue" button.
This page was last revised March 6, 2009. Its address is http://udel.edu/~mcdonald/evolvulator.html.
©2009 by John H. McDonald. You can probably do what you want with this content; see the permissions page for details.