Squirm3 > EvSelfReps > Exp3

Evolvable Self-Replicating Molecules in an
Artificial Chemistry

Experiment 3: Spontaneous appearance of self-replicators

Below the experiment is running as a java applet - if you don't see anything then you either need to change your browser settings to enable java, or use a different browser.

You can control how fast the applet runs by using the slowdown controls, if enabled they cause a delay of so many milliseconds per timestep. Remember to hit 'update applet' after changing the value.

The flood controls let you specify whether you want the flood to occur and, if so, how often. The default value of 200000 timesteps was the one reported in the paper for this experiment. The flood clears out one half of the area and replenishes it with more 'raw material' - atoms of random type with state 0. Use 'update applet' after changing the values.

The cosmic ray probability controls let you specify the probability that an atom's state will be randomized at each timestep. Use 'update applet' after changing the values.

If you want maximum speed then there are controls that let you draw only every 100 timesteps, for example. If you really want maximum speed then take a look at the C++ version on the development page.

The 'pause/run' button is a toggle switch that lets you stop and start the applet.

When you hover over the atoms with the mouse their type and state are displayed. This works best when the applet is paused.

To reset the applet, use your browser's Refresh button.

Slowdown: milliseconds
Flood every: timesteps (alternates left and right)
Cosmic-ray state change probability: per atom per timestep
Draw only every: timesteps


This experiment can take a long time to produce results. Small clumps of atoms will form after a few thousand timesteps. These tend to grow and can become unable to move - four atoms bonded in a square, for example, are stuck (in this 2D square grid implementation of the chemistry). Note that the overall rate of reactions occurring is much smaller than the previous experiments, the world is relatively inert. It is only when self-replicators come along that reactions occur frequently.

It can take several hundred thousand timesteps before the first self-replicators appear. But when they do the chemistry changes rapidly. On a plot of the average reaction rate over time is is obvious where the self-replicators appeared because there is a sudden jump - the self-replicators are catalysts.

The java source for this applet is here: sq3.zip (13k) - for instructions on building the source see the development page.