Replies

lol! So you really don't know anything about the Cambrian and the organisms existing at the time, you don't know anything about Precambrian organisms, and you don't know anything about the changes in habitat and genetic innovations at the time, yet you find it all incredibly problematic?

The term "Cambrian Explosion" is falling by the wayside as we find out it really wasn't an explosion after all, any more than there was a "Permian Explosion" of mammal-like reptiles or a "Cretaceous Explosion" of dinosaurs or a "Tertiary Explosion" of mammals. The Cambrian organisms had their roots in Precambrian organisms--the impression Creationists give is that there was no life before the Cambrian.

The Cambrian is interesting because of the innovation in body plans in larger metazoans than had been present before. There are a variety of reasons for this. Increasing oxygen concentration may have allowed larger organisms to develop. The Hox genes which control body patterning appeared about this time. The success of one type of organism in increasing body size could have triggered the evolution of more larger organisms by providing a large prey source to munch on.

The other myth creationists have is that most modern phyla popped into existence, as if one day there was nothing and the next day modern sponges, clams, and crabs. This is not the case. Many modern phyla did have their roots in the Cambrian, but the first Cambrian organisms are difficult to classify. Many have traits that might place them into multiple phyla (can you imagine looking at a modern organism and wondering whether it's a worm, an arthropod, or a mollusc?) This is because the modern phyla share a common ancestor in one of these strange Cambrian creatures, so in the earliest organisms we see mixed traits from both phyla. Populations descended from these organisms would have evolved along their own lines and lost some ancestral traits while adding new ones. So the first Cambrian organisms are what we would call "stem group" organisms (an ancestral group that shares diagnostic traits with a modern phylum while also having traits that don't match), while their eventual descendants that are in the modern phylum are called "crown group" organisms.

When we study the Cambrian organisms we see that in the early Cambrian there are many enigmatic organisms, while the late Cambrian organisms millions of years later have begun to evolve along separate lines and are much easier to classify into modern phyla.

The evolutionary process in the Cambrian took place over millions of years and is consistent with evolutionary theory.