The purpose of the Intelligent design (ID) movement is to put a new face on old-fashioned creationism – like spraying a rotting carcass with air-freshener, but it doesn’t even cover up the odor. The cornerstone of ID is irreducible complexity, which is literally just a new name for the old god-of-the-gaps nonsense. ID’ers say that there are structures in biology that are too complex to have evolved, because they could not function if they were any less complex. Their complexity is irreducible, so evolution has not path it could have taken to get there, and chance alone is too improbable.

The weakness of this argument is that it is an argument based upon ignorance – what we currently do not know. Saying something is irreducibly complex, in practice, amounts to pointing at the current gaps in our knowledge of how certain structures evolved, and saying that those gaps are irreducible and therefore they are the product of an intelligent designer. God of the gaps is now ID of the gaps, and irreducible complexity is the gaps.

But this line of argument is dependent on what we currently do not know, and that is a moving target, because biologists are discovering all the time new information which reduces the allegedly irreducible. In the Dover trial of 2005 evidence was presented that essentially all of the examples of irreducible complexity presented by Michael Behe had since been reduced. The gaps were filled in. That Behe still maintains his position was branded by the conservative judge as intellectual dishonesty.

Behe and his cohort also ignore the primary theoretical rebuttal to their position – structures may be irreducible in their current function, but they could have evolved from a simpler structure that serves a simpler function. So called coaptation pulls the theoretical rug out from irreducible complexity. IDers have no response to this except to move the goalpost by saying, “Prove that that is what happened in fact, not just theoretically.” Of course, when this is done they just migrate over to a new gap.

Still, I revel whenever a new gap is closed, a complex structure reduced. A new study does just that. The gap in question is the complex set of proteins that make up the synapse – the connection between two nerve cells.  The researchers here are exploiting the available of sequenced genomes from multiple species. We can now make comparisons of genes across species, and therefore across different evolutionary pathways.

What they looked at in this case is the sponge – a very primitive animal that has no nervous system. This gives us a window into the common ancestor between sponges and other animals, a creature that also must have lacked a nervous system. I turns out that sponges, specifically Amphimedon queenslandica, have almost the complete set of genes for post-synaptic proteins – proteins that make up the structures on the receiving end of the synapse. Some of the genes demonstrate complete or near complete conservation, which means they are identical to the human version of the genes. Further they are expressed in those cells that would be the precursor to nervous tissue.

The authors write:

The data presented here support the presence of a proto-post-synaptic scaffold in the last common ancestor to all living animals. The presence of a large number of post-synaptic genes in the genome of demosponge Amphimedon, the nearly absolute conservation of binding domains and ligands between this sponge and animals with neurons, as well as the expression of a set of post-synaptic mRNAs in the same cell type, suggest the proto-post-synaptic scaffold existed as an assembled functional structure very early in animal evolution.

What this amounts to is stunning evidence for an evolutionary relationship between sponges and other animals, including humans. And that the complex structure of the synapse has it roots in the structures that existed before nerves and synapses evolved. The authors further write:

The Amphimedon cell type that most prominently expresses the post-synaptic orthologs is the flask cell found in larva and characterized by a deep cilium and a large population of basal vesicles. The flask cell may have some environmental sensing properties that require membrane specializations and perhaps reflect an evolutionary intermediate and a cell type that served as a starting point for the evolution of neurons.

There is no non-evolutionary explanation for this type of evidence, and this is just one tiny slice of the evidence. There are countless other independent lines of evidence that also establish a clear evolutionary history for life on earth.

But there will also always be gaps. That is the nature of science. It is completely disingenuous for creationists to look at a snapshot of the scientific evidence for evolution and say, “Aha, there are gaps.” They are thereby claiming that if evolution were true there would be no gaps, and this is utter nonsense. It is more appropriate to look at how the gaps in our ability to explain the history of life through evolution have changed over historical time. If we take this view we see that the gaps have been constantly shrinking. As we gather more and more evidence, the unknowns are getting smaller and smaller. The evidence for evolution has been building over time, and that is a testament to its explanatory power and its ultimate correctness.

Moreover, creationists have been in constant retreat from this evidence. Every time they offer up a gap to harp on, it gets closed. First they said there was no evidence for a type of inheritance that allows for evolution, but then genetics were discovered. Then they said there was no fossil evidence for change over time, but the fossils just keep pouring in. They said that there was no evidence for the evolution of whales form terrestrial mammals, but then we discovered Ambulocetus – a half whale with tiny legs.

Irreducible complexity is really just a strategy for retreating further from the evidence – away from anything that can be documented with fossils. Behe used as his example of gaps microscopic structures and biochemical pathways that do not fossilize. But the creationists could not hide even there, because our technology for sequencing DNA has allowed us to peer at the very basis for all biology. They really have no place left to hide. But that does not mean they will give up – as ideologues they will never surrender to the evidence. They have proven that they have a limitless capacity to distort the evidence, to move the goalpost, and when necessary to simply lie.