Is “convergent evolution” a convenient escape clause for evidence that contradicts evolution?
Evolutionary theory has a classification scheme that cannot lose. Darwin’s original tree diagram described “divergent evolution,” a process beginning with speciation followed by the accumulation of variations that make the two branches more and more dissimilar over time. Animals with similar structures on the same branch are said to have “homologous” traits, because they derive from the same common ancestor. But the living world is filled with traits that resemble each other on different branches. What caused that? Ah, the evolutionist replies: those traits are due to “convergent evolution.” The similarities are “analogous” traits, because they do not derive from the same common ancestor. With this classification scheme, evolution explains everything: if similar animals are related, they evolved; if they are unrelated, they evolved. Is this a description of reality, or rather a convenient strategy for rendering evolution immune from falsification? Here are some recent examples of “convergent evolution” from the literature.
Jelly-Bird: PhysOrg wrote, “Ion selectivity in neuronal signaling channels evolved twice in animals.” Sea anemones and birds have complex channels in their cell membranes called voltage-gated sodium channels, responsible for passing signals along nerves. Yet their respective branches on the tree of life supposedly separated 600 million years ago. The channels in the marine invertebrates “differ from those found in higher animals, yet show the same selectivity for sodium.” Thus, “This study shows that different parts of the channel changed in a convergent manner during the evolution of cnidarians and higher animals in order to perform the same task, namely to select for sodium ions,” the article alleged. “This demonstrates that important components for the functional nervous systems evolved twice in basal and higher animals, which suggests that more complex nervous systems that rely on such ion-selective channels could have also evolved twice independently.”
Jelly-Man: Nature News claims that muscles, too, evolved twice. In “Evolutionary biology: Muscle’s Dual Origins” (12 July 2012), Andreas Hejnol said, “Jellyfish move using a set of muscles that look remarkably similar to striated muscles in vertebrates. However, new data show that the two muscle types contain different molecules, implying that they evolved independently.” Adding to the puzzle is the fact that comb jellies, on a different branch, also have striated muscles, while most other invertebrates do not. “Whether this comb jelly’s striated muscle is related to that of jellyfish or vertebrates, or represents another convergent evolution event, remains to be determined.” The claims become even more astonishing:
These results suggest that, despite their remarkable physical resemblance, the striated muscles of jellyfish and humans are constructed using a vastly different set of genes. Steinmetz and colleagues have revealed an extraordinary instance of convergent evolution — the evolution of highly similar traits in distantly related organisms.
Remarkable, exquisite, striking: Another paper in Nature begins, “In a remarkable example of convergent evolution, insect species spanning 300 million years of divergence have evolved identical single-amino-acid substitutions that confer resistance to plant cardenolide toxins.” This is not as dramatic a convergence as the previous two, because the trait involves one amino acid substitution, and the species are all insects. The authors, though, thought this really something: they said it “represents an exquisite case of convergent molecular evolution, in which distantly related insect species have evolved a common adaptive response in a single gene.” What makes it “a striking case of convergent molecular evolution” is that the common trait occurred 4 times in unrelated insects that feed on the same kind of host plant. The authors dressed up this “textbook example of convergent evolution at the molecular level” with adjectives like “autoecological convergence” and “functional convergence.” (Whiteman and Mooney, “Evolutionary biology: Insects converge on resistance,” Nature 489, 20 Sept 2012, pp. 376–377, doi:10.1038/489376a.)
The nose knows: The concept of convergent evolution shows up in two papers in PLoS Biology about olfaction (the sense of smell). Fruit fly maggots and humans could hardly be further apart in the evolutionary tree, but three Cambridge evolutionists found an “unpredicted degree of similarity” between their odor-detection equipment. They said, “Our results reveal an unexpected degree of similarity between the development of the olfactory systems in vertebrates and the Drosophila larva.” (Prieto-Godino LL, Diegelmann S, Bate M (2012) Embryonic Origin of Olfactory Circuitry in Drosophila: Contact and Activity-Mediated Interactions Pattern Connectivity in the Antennal Lobe. PLoS Biol 10(10): e1001400. doi:10.1371/journal.pbio.1001400). In the same journal, Janelle Weaver commented on the surprise without using the “convergent evolution” phrase specifically: “The findings reveal surprising similarities between vertebrates and insect embryos in the formation of olfactory networks.” She even ventured a philosophical explanation: “Because neural circuits in other sensory and motor systems share similar properties, the findings may represent general mechanisms that underlie the development of networks in the nervous system.” (Weaver J (2012) Striking Similarities in Fly and Vertebrate Olfactory Network Formation. PLoS Biol 10(10): e1001401. doi:10.1371/journal.pbio.1001401.) Note: Weaver did not mention evolution in her summary, but did neither did she disagree with the other paper’s references to evolution.
Convergent bloodsuckers: A paper about fleas in PLoS ONE states, “Blood feeding evolved at least ten times within arthropods, providing a scenario of convergent evolution for the solution of the salivary potion.” (Ribeiro JMC, Assumpção TCF, Ma D, Alvarenga PH, Pham VM, et al. (2012) An Insight into the Sialotranscriptome of the Cat Flea, Ctenocephalides felis. PLoS ONE 7(9): e44612. doi:10.1371/journal.pone.0044612.)
Convergent crayfish: Another paper in PLoS ONE found convergent evolution in 12 subgenera of Appalachian crayfish. They couldn’t get the subgenera into the same monophyletic tree, so they had to use convergence to explain the similarities. They referred to a previous study that “suggested that convergent evolution was more common in invertebrates than previously thought.” Not only that, they figured that convergence is all over the place, confounding the work of taxonomists to figure out what’s related to what:
We find convergent evolution has impacted the morphological features used to delimit Cambarus subgenera. Studies of the crayfish genus Orconectes have shown gonopod morphology used to delimit subgenera is also affected by convergent evolution. This suggests that morphological diagnoses based on traditional crayfish taxonomy might be confounded by convergent evolution across the cambarids and has little utility in diagnosing relationships or defining natural groups. We further suggest that convergent morphological evolution appears to be a common occurrence in invertebrates suggesting the need for careful phylogenetically based interpretations of morphological evolution in invertebrate systematics. (Breinholt JW, Porter ML, Crandall KA (2012) Testing Phylogenetic Hypotheses of the Subgenera of the Freshwater Crayfish Genus Cambarus (Decapoda: Cambaridae). PLoS ONE 7(9): e46105. doi:10.1371/journal.pone.0046105.)
Convergent everything: When you find similarities between plants, invertebrate animals and vertebrate animals, you have a real conundrum; yet all three unrelated groups show similar signaling pathways in their innate immune systems. This led Frederick M Ausubel to reject divergence and embrace convergence (“Are innate immune signaling pathways in plants and animals conserved?” Nature Immunology 6, 973 — 979 (2005), 21 September 2005 | doi:10.1038/ni1253):
It is commonly reported that these similarities in innate immunity represent a process of divergent evolution from an ancient unicellular eukaryote that pre-dated the divergence of the plant and animal kingdoms. However, at present, data suggest that the seemingly analogous regulatory modules used in plant and animal innate immunity are a consequence of convergent evolution and reflect inherent constraints on how an innate immune system can be constructed.
In that quote, Ausubel used a common explanatory device to explain why traits on vastly unrelated organisms end up being alike: nature imposes constraints on how systems can be constructed. For instance, if a creature wants to fly, it needs wings. That’s a requirement. Birds, flying insects, pterosaurs and bats, therefore, all had to obey that design requirement in order to fly. It could be argued, however, that animals could have evolved rockets or helicopter blades (discounting unpowered gliders like maple seeds). There’s often more than one solution to an engineering challenge.
The Wikipedia entry on “Convergent Evolution” shows that the concept has undergone a bit of taxonomic diversification itself: there’s functional convergence, homoplasy, synapomorphy, parallel evolution, re-evolution and evolutionary relay. Convergence might be detected at the morphological level or at the molecular level. As for causes of convergent evolution, the article claims that animals with similar niches are likely to evolve similar equipment. And yet that can hardly be a “law of nature,” because many organisms occupy similar niches without “convergent” traits. Thus, they are divergent except when they are convergent – an explanation that explains opposite concepts.
Wikipedia’s article ends with a statement that reveals that “convergent evolution” is an incomplete and controversial notion:
Convergence has been associated with Darwinian evolution in the popular imagination since at least the 1940s.… The degree to which convergence affects the products of evolution is the subject of a popular controversy. In his book Wonderful Life, Stephen Jay Gould argues that if the tape of life were re-wound and played back, life would have taken a very different course. Simon Conway Morris counters this argument, arguing that convergence is a dominant force in evolution, and that, since the same environmental and physical constraints act on all life, there is an “optimum” body plan that life will inevitably evolve toward, with evolution bound to stumble upon intelligence — a trait of primates, crows, and dolphins — at some point. Convergence is difficult to quantify, so progress on this issue may require exploitation of engineering specifications (e.g., of wing aerodynamics) and comparably rigorous measures of “very different course” in terms of phylogenetic (molecular) distances.
It may be a work in progress, but it’s a convenient phrase for evolutionists to toss around in their papers.
A constraint can no more evolve a trait than a stop sign can evolve a car. An “engineering specification” can no more cause a system to emerge than air can create an airplane. These guys are kidding themselves. One of the above spoke of “general mechanisms that underlie the development” of such-and-such a complex system. What are these guys, Platonists? Is there some Universal Form that gets impressed on the evolving animal? As Randy Guliuzza explained in a series of articles on ICR, evolutionists are tricksters, transferring the “natural selector” to the environment, as if a blind world could force organisms into the engineering department. He argues that ability to adapt had to be “designed in” to the organism by a Creator who doesn’t have any more to learn about engineering.
What the evolutionists have concocted with their term “convergent evolution” is a strategy for avoiding falsification. Let’s assume for the sake of argument that there really is a Creator, and one of his designs for preventing people from believing in evolution (i.e., that nature created itself) was to create complex organisms in nested hierarchies with similarities across hierarchies and within hierarchies, with all organisms using the same basic genetic code. This is the argument Walter ReMine elaborated in his book, The Biotic Message: it would reveal a single Creator who did not use an evolutionary process. The complexity rules out chance, the universal genetic code rules out polytheism, and the similarities across hierarchies rule out Darwinism. This is what we see in the living world. Rather than follow the clear biotic message, though, man’s willful ignorance leads him to concoct schemes to imagine evolution in spite of the evidence.
Clever phraseology, like “convergent evolution,” to escape being cornered, is never an argument. It’s a dodge. The desperation of some evolutionists to maintain their belief in spite of the biotic message is revealed by how they will multiply miracles to avoid the obvious. For instance, they will flippantly point to cases where their faith requires them to believe that complex traits evolved two, three, or more than a dozen times independently (examples: 9/20/2011, 7/27/2011 #9, 2/25/2011 #1, 11/10/2010 #2, 1/16/2003) Even the pro-Darwin Wikipedia page shows incredible cases of convergence, like skulls of a thylacine (marsupial wolf) and gray wolf that, though unrelated, are similar in many detailed points.
“Convergent evolution” is also an insult to the Creator who has revealed His wisdom so clearly in the intricate systems of life. Like Guliuzza pointed out, natural selection is not a design process. It’s not a process at all, any more than monkeys playing pinball with no banana. It’s not a mechanism for development, either. It’s nothing; it’s just “stuff happens.” Evolutionists use magic words to try to make it into a designer substitute. The only thing that should converge when we look at this world filled with wonderful engineering designs, often similar among unrelated groups, is agreement that it is due to “common design.” Such a simple, elegant theory is foreign to the ears of those who reject God, but the facts of nature support creation, not “convergent evolution.”
For a host of remarkable examples of similarities among unrelated groups, see Brett Miller’s humorous but penetrating essay, “The Convergence Concoction” on EvidentCreation.com.