I love watching illusionists. They perform feats that seem to defy the very laws of physics- cutting people in half (who live to tell about it), disappearing and reappearing, escapes, and many, many others. It is interesting that we see all these things "magically" happen, but we know that they could not happen unless the illusionist was involved. The illusionist has a purpose for making something "appear" or "disappear." They wish to impress and entertain their audience. They usually pick an object with a certain level of complexity that is easily recognizable- a ball, a playing card, or dove or rabbit for instance. They carefully prepare the environment for the illusion; often the audience is a witness to this setup. Now, if any of those objects just appeared on stage (or in the street for that matter), we would not think for a moment that it "just happened" with no explanation. We would immediately look for a cause, a purposeful agent who designed and orchestrated the stunt.
Appearing Acts in Nature
The Cambrian and Avalon explosions are quite analogous to the appearance of an object by an illusionist. These acts were complete with the setup of the environment and everything. In his book "Navigating Genesis" Dr. Hugh Ross explains what has been discovered in nature and how it argues for a purposeful agent behind the setup and execution of the appearances:
"Only through billions of years of photosynthetic activity could Earth's atmosphere and oceans build up sufficient oxygen to support animal life. The very moment oxygen reached appropriate levels, the Avalon and Cambrian explosions occurred. The lack of any appreciable gap between the time of oxygen's rise to minimum life-sustaining levels and the appearance of animals argues strongly for the involvement of a purposeful Creator."