Those strange sounds you may have been hearing recently could be the wailing and gnashing of teeth that is surely emanating from the headquarters of the Discovery Institute (better known as the Disco Institute) following the publication of new research that suggests the Cambrian “explosion” might not have been quite as, well, explosive as previously thought.
A click above will link you to an article on Phys.org discussing the new research, which concerns the fossil of a tiny sponge, smaller than a grain of sand. The reason you care is because the fossil dates to about 600 million years ago, about 60 million years earlier than the aforementioned “explosion.”
The Cambrian explosion, if you’re unfamiliar, refers to the “sudden” (geologically and evolutionarily speaking — it lasted about 20 million years) appearance in the fossil record of most major extant animal phyla, including — you guessed it — sponges (phyla: Porifera).
Proponents of young-earth creationism claim the Cambrian explosion as support for their view because they argue this time frame is too short for evolution to operate (it’s not) and that we’ve never discovered ancestral forms for the phyla that appeared during this period (we have). But anyway.
I personally never put much stock in this whole argument, on either side, because it’s so speculative and relies so heavily on the assumption that the fossil record is a more or less complete and reliable account of the history of life on earth. Which, in fact, we know it is not. It’s the rock version of the argument from silence.
Just as easily as anti-evolutionists can assume that the Cambrian phyla had no ancestral forms (except for the ones for which we have, in fact, found fossils of ancestral species), we can assume that the phyla did have ancestral forms, but they were either not preserved in the fossil record, or their remains have yet to be discovered.
This new research suggests the latter. From Phys.org (emphasis mine):
Though some evidence, including molecular clocks, has already pointed to sponges evolving earlier, this fossil shows that the Cambrian explosion might not be a period when a large number of new traits emerged, but a period when a large number of fossils could be preserved, as animals during the Cambrian grew larger and gained skeletons.
“This specimen is of an animal that had already evolved a number of fundamental sponge traits,” [study co-author David] Bottjer said. “It implies that by the time this animal was living, most of the developmental genes for sponges had evolved.”
Though I never took the whole “explosion” that seriously, the fellas up at the Disco Institute (who, I should note, do reject evolution, at least on some level, but are generally not young-earthers) are not like me. They have, in fact, put a lot of their eggs in the Cambrian “explosion” basket. Case in point, the publication of “Darwin’s Doubt” by their employee, Stephen Meyer.
The book is nothing but one long, valiant effort to shoehorn the Cambrian explosion into supporting intelligent design, and they have hailed its publication as one of their top accomplishments in recent history (though it was published almost two years ago now, their blog still continues to reference it at least once or twice a week).
How will they respond to new evidence suggesting the Cambrian explosion was not really an “explosion” at all, but simply a particularly unpropitious failing of what we already know to be an imperfect recording system? Only time will tell, but it should be entertaining.
Link to the original paper, published in PNAS in March.