Convergence in Catfish Venomous for Evolution
New Research Raises Questions about Evolution, Supports Intelligent Design
While working for Procter & Gamble, I was involved in a project that required me to travel frequently to a chemical plant in Batesville, Arkansas. While there, our hosts often “treated” us to a meal that featured deep-fried catfish, a local “specialty.”
I don’t care much for fish and I didn’t enjoy the catfish meal the first time I had it. Even though I didn’t wish to repeat the experience, our hosts took us out for catfish dinner every time we visited Batesville. So I just learned to expect it.
Catfish have recently caused problems for evolutionary biologists as well. Researchers have discovered an unanticipated example of convergence (repeated occurrence) involving catfish, one that causes them as much indigestion as the fried catfish caused me. It turns out the venom glands of poisonous catfish must have had at least two independent origin events, if viewed from an evolutionary perspective.
As I’ve previously pointed out, given the nature of its mechanism, evolution shouldn’t repeat itself, because it’s a historically contingent process. (See here and here for a more detailed discussion of this point.) And yet, over the last decade or so, evolutionary biologists have discovered a number of examples of convergence at the organismal and biochemical levels. In his book, Life’s Solution, paleontologist Simon Conway Morris describes numerous examples of morphological and behavioral convergence.
But convergence isn’t confined to macroscopic systems. As I describe in The Cell’s Design, when viewed from an evolutionary perspective, a number of life’s molecules and processes, though virtually identical, appear to have originated independently, multiple times.
New work by a scientist from the University of Michigan serves as one of the few detailed studies on the origin of venomous glands in fish. This investigator studied over 150 different species representing all the known species of catfish. Based on his examination, he concluded that between 1,250 to 1,600 species of catfish possess venom glands, far exceeding previous estimates.
Anatomical characterization reveals the venom glands are associated with sharp, bony spines along the leading edge of the catfish fins. When the spines puncture another fish, the membrane surrounding the venom-producing cells rips, thus releasing poison. The venoms generated by catfish cause a variety of effects including pain, muscle spasms, tissue damage, and respiratory distress.
When trying to account for the origin of venom glands in catfish from an evolutionary perspective, it appears as if these structures must have emerged at least two separate times. It also seems as if the evolutionary pathway leading to the emergence of toxin glands and associated structures was the same as well, with the gland toxins apparently derived from other skin compounds.
It is remarkable to think that a complex biological system like this would emerge independently on at least two separate occasions.
The widespread occurrences of convergence at the organismal and molecular level are unexpected given the nature of the evolutionary process. Biological convergence provides very real justification for skepticism about the idea that evolutionary mechanisms alone account for life’s history and diversity. On the other hand, the repeated, independent origins of complex systems make sense from a creation viewpoint. It is reasonable, then, to expect that the Creator would reuse good designs.
When served catfish by our well-meaning hosts, I thanked them for their hospitality and politely did my best to choke it down. But I have a hard time swallowing the idea that biological convergence can be explained apart from the work of a Creator.