The "problem" is how to account for the very rapid appearance of complex animals about 530 million years ago. Intelligent Design Creationists think that they can ignore all of the evidence for evolution for the following 530 million years and focus on this one problem to discredit naturalistic explanations for the history of life.
You might expect that they would offer an alternative explanation. Like, perhaps, an intelligent being who visited Earth 530 million years ago, created a bunch of different animals with similar body plans, then allowed evolution to proceed for the next half a billion years?
Don't hold your breath waiting for a scientific explanation. They aren't that clever.
I'm interested in the arguments that Stephen C. Meyer proposes to deal with the science that doesn't conform to his worldview. In this case, it's the molecular evidence that he dismisses in the Chapter called "The Genes Tell the Story." I summarized the chapter in: Darwin's Doubt: The Genes Tell the Story?. I also discussed the issue in a post from a few years ago: The Cambrian Conundrum: Fossils vs Genes.
Scientists wondered whether molecular data could shed some light on the Cambrian Explosion. If the various species radiated quickly then the sequences of the genes of their descendants might show this. On the other hand, if the animals of the various phyla arose more gradually over a long period of time then the molecular evidence might show much deeper roots supporting the idea of a long fuse. In that case, the absence of a long chain of transitional fossils might be an artifact of some sort.
The result of this experiment is embarrassing to Stephen C. Meyer so he has to discredit the work in order to support his (nonexistent) alternative explanation. As I explained before, he has five objections. The first one is that the fossil record doesn't support the molecular data!
... there is now good reason to doubt this allegedly overwhelming genetic evidence. In the idiom of our forensic metaphor, other material witnesses (fossils) have already come forward to testify ....He then goes on to explain that the molecular data suggests deep divergence. But the problem with deep divergence is that there are no fossils to support it.
Any plausible ancestor to such organisms would have likely left some hard body parts, yet none have been found in the Precambrian. Yet the deep-divergence hypothesis, whatever its other merits, requires a viable artifact hypothesis to explain the absence of fossilized Precambrian ancestors.Here's a short summary of Stephen Meyer's first argument.
- There are no obvious precursors to the Cambrian animals in the fossil record.
- Scientists looked to molecular data to test various hypotheses; namely, whether there was rapid radiation or whether the explosion might be an artifact of the fossil record.
- The molecular evidence shows deep divergence, indicating that there are probably missing precursors to the existing Cambrian fossils.
- The molecular evidence must be rejected because there are missing fossils.1
1. That's because absence of evidence is strong evidence of absence. So strong, in fact, that it trumps some real evidence of presence.