What exactly is the cambrian explosion and how is it related to evolution?

The Cambrian Explosion was a “sudden” appearance of a wide range of fossils from complex species around 540 million years ago. There is a lot of debate in the scientific community as to what would cause development of so many complex species in such a relatively short period of time. Some creationists have tried to claim the explosion is evidence against the theory of evolution, since so many types of animal can be found in one place, rather than over a gradual period of time as natural selection would seem to explain.

However, there are quite a few transitionary fossils in the Cambrian layer, such as lobopods and intermediaries between worms and arthropods. Also, the Cambrian Explosion is not quite as diverse or explosive as some people claim; there are quite a few phyla that are pre and post Cambrian (bear in mind that a phyla is the second largest categorization of living things, so we’re talking thousands of species, perhaps millions). Finally, there are several possible explanations for what caused the explosion. For example, the environment may have been more favorable to the spread of life during the Cambrian period (it followed an Ice Age). There were other environmental factors such as oxygen content of the atmosphere, phosphate content in the oceans, etc. And, it may simply be that we don’t yet know enough about the development of species during this period to make a definite conclusion; deciding that intelligent design is valid is not necessarily the right course of action.