If you google ‘front-loading evolution,’ there are three hits on the front and second page that attempt to refute this hypothesis. Let’s have a look.
First, Ed Brayton argues:
And while front loading means those genes had to be “turned off” for hundreds of millions of years, exaptation posits that those genes were turned on, expressed in the phenotype and serving different functions. Thus, exaptation is consistent with the preservation of those genes while front loading is not.
Equally as important, while front loading presumes that those genes serve no function before they are later expressed, exaptation predicts that they must have some function if they are highly preserved over a long period of time. They simply must be expressed in the phenotype for some function or they will mutate in to uselessness. And that is exactly the case here, as this study found that those genes, though virtually identical between sponges and humans, serve a different function in sponges than they do in humans (obviously so, since the sponges have no nervous system).
There are only two ways out of this for ID advocates: either they have to accept that those front-loaded genes had different functions in earlier species (which effectively makes front loading synonymous with exaptation, rendering the idea meaningless) or they have to posit that God not only loaded the genes for all those later developments in to earlier organisms that didn’t need them, but he also put some sort of mystical force field around them to prevent them from mutating over the last 4 billion years.
The other problem, of course, is that no one has ever found an organism that has all of the genes needed for later developments (feathers, wings, lungs, flagella, etc); that is, no organism actually has a fully complete genome front-loaded with all the goodies to be used later. If front loading was true, then the prokaryotes – the earliest existing life form on Earth – should have all of those genes. They don’t, of course. The bottom line is that the evolutionary hypothesis, exaptation, predicts the evidence perfectly; the ID hypothesis is flatly contradicted by it and can only try to explain it away or invent mystical and unknown processes to circumvent the evidence.
Next, Allen MacNeill argues:
This evolutionary argument is now being strongly supported by findings in the field of evolutionary development (“evo-devo”), in which arguments based on “deep homology” are providing explanations for at least some of the seemingly amazing convergences we see in widely separated groups of organisms. Recent discoveries about gene regulation via hierarchical sets of regulatory genes indicate that these genes have been conserved through deep evolutionary time, from the first bilaterally symmetric metazoans to the latest placental mammals, as shown by their relative positions in the genome and relatively invariant nucleotide sequences. These genes channel the arrangement of overall anatomy and body form throughout the course of development, producing the overall shapes of organisms and the relationships between body parts that we refer to when discussing evolutionary convergence.
However, as should be obvious by now, this in no way provides evidence for the currently popular ID hypothesis of “front-loading”, except insofar that it states that the hierarchical control of overall development evolved very early among the metazoa. It provides no empirically testable way to distinguish between an evolutionary explanation and a “design” explanation. Indeed, all of the evidence to date could be explained using either theory.
And so, by the rules of empirical science, since the evolutionary explanation is both sufficient to explain the phenomena and does not require causes that are outside of nature (i.e. a supernatural designer, that is neither itself natural nor works through natural – i.e. material and efficient – causes), evolutionary biologists are fully justified in accepting the evolutionary explanation (and disregarding the “front-loaded ID” explanation.)
Finally, Henry Neufeld argues:
But there are two important ways of looking at the general design of the universe that are very important to distinguish. The first is called frontloading. “Frontloading” refers to the idea that God placed certain design elements into the universe, or into life at the beginning. For example, one can assume that God created the first life-form and put certain elements in its DNA that would eventually result in complex structures. It seems to me that this notion could be tested, because one should find apparent “junk” DNA in early creatures that looks like the DNA that creates complex structures in later life forms.
In the next entry, I will show how these criticisms fail.