One of the more popular arguments used by anti-evolutionists is the supposed difficulty of order arising from chaos, and complexity from simplicity. Though not directly in the field of evolutionary theory, there is an analogue in the field of computation, specifically from the area concerned with cellular automata. This analogue, called John Conway's Game of Life
, shows how very rapidly order and complexity can come about from a complete mess. More than that, coordinated, self-replicating and/or motile arrangements often occur quite spontaneously.
In the analogue, it is convenient to think of the cellular automata as organisms, the playing field, including the cellular automata on it, as the environment, and the rules (being four very simple ones) by which they live, procreate or die as the laws of nature in that environment. An initial playing field arrangement that is completely random is commonly used. The energy for moving forward through the generations ultimately comes, as it does in real life on Earth, from the Sun.
The simulations become especially interesting when the rules are applied probabilistically, rather than rigidly adhered to, i.e. there is an individual probability assigned to each of the rules as to whether it is applied or not. Unfortunately, I know of no web-based simulator that permits this modification, but the results are even more surprising and illustrative.