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Convergent Evolution: An Argument That Comes at a Price

Photo: Dolphins, by Gregory “Slobirdr” Smith [CC BY-SA 2.0], via Wikimedia Commons.

Can the laws of nature explain the biological information in human beings and other creatures? In his recent book The Compatibility of Evolution and Design, theologian Rope Kojonen argues that they can. My colleagues and I reviewed the book in the journal Religions and have been critiquing it here.

I turn now to convergent evolution, which is Kojonen’s strongest positive argument for the laws of form, or what he calls the “library of forms.” This argument is significant because these laws of form play a crucial role in Kojonen’s positive case for design. In his view, the laws of form arise from designed laws of nature and, in turn, they vitally shape the “fine-tuned” preconditions that help make evolution possible. So, Kojonen’s convergence argument is a crucial part of his case for design. It also plays a key role in his account of how design supplements evolutionary processes in just the right way.

To understand why this is problematic, it helps to know more about convergence. Kojonen says that convergence means “the independent evolution of the same biological outcome in two or more different lineages, beginning from different starting points” (Kojonen 2021, p. 125). He notes, for example, that “dolphins and sharks have similar streamlined bodies and dorsal fins, even though dolphins are mammals and sharks are fish.” He also says that “paddle-shaped limbs for swimming have evolved independently seven times, and a structure as complex as the eye has evolved independently 49 times…” (p. 125). The word “convergent” is used to describe these examples because, in general, multiple lines of evidence — usually from genetics, paleontology, biochemistry, systematics, and similar fields — indicate that it is hard to make a coherent phylogenetic account of how they came to be from a given common ancestor. Under the idea of common ancestry, these facts are considered odd. Thus, evolutionists say that they are the result of convergent evolution.

A Stacked Deck

Kojonen sees this convergence as evidence that laws of form “play a significant role” in helping evolutionary processes cluster around similar solutions (p. 125). He comes to the conclusion that convergence shows “functional constraints have a big effect on the evolution of life like that on Earth” (p. 127). The general idea, expressed as a rhetorical question, seems to be: If the same solutions came up independently over and over again, doesn’t that suggest that the deck was probably stacked to help evolution succeed? 

The first problem is that convergence needs not only to evolve certain complex proteins, traits, and systems but also to evolve these things on their own more than once. If proteins are rare and isolated (as our review establishes) and the chances of even a single short protein evolving once in the whole history of the earth are too low, then, all other things being equal, the chances of similar proteins evolving more than once are even lower. This is amplified when scaled up to protein complexes, cell types, tissues, and organs, again demonstrating why the strength of the scientific evidence is crucial. If unguided evolution was not the cause of convergence, Kojonen’s argument that convergence supports the reconciliation of evolution and design would also fall apart.

A Dilemma

Second, and more importantly, Kojonen’s model is stuck in a paradox. This problem is a version of “Sober’s Paradox,” which is a term used by philosopher of biology Paul Nelson (Nelson 2022). Kojonen’s ideas about common ancestry and his ideas about convergence are at odds with each other. His attempt to agree with both sides breaks up the model internally.

Accept Convergence, Lose Common Ancestry

For instance, if convergence of forms is the result of being constrained by the laws of physics and chemistry, then Kojonen’s co-option response to Behe’s argument about irreducible complexity loses some of its power. This is because co-option only makes sense if there are similar protein parts in other systems that could be changed into the specialized parts needed for the bacterial flagellum. Kojonen says this about the flagellum: “The fact that similar parts exist in other systems, for example, does show that evolution is possible” (p. 118). But with “convergent evolution,” parts or systems that are even more complicated than the flagellum of a bacterium can develop without any similarity or common ancestry. If that’s true, what real power does co-option have?

Let’s also think about how true evolutionary convergence hurts Kojonen’s case that proteins evolved over time. As the story goes, mutation and natural selection can transform one functional protein into another. But if convergence is happening, wouldn’t it be easier for evolution to just make a new protein? Otherwise, if it is just as likely that evolution can lead to big changes as it is to lead to small ones, why talk about gradual changes moving one functional protein to another? Again, the argument has lost its power.

As we’ve seen, Kojonen’s belief in evolutionary convergence hurts the case for common ancestry in standard evolutionary theory. Evolutionary biologists usually think that similar structures can best be explained by having a common ancestor with a similar structure, i.e., it is far more likely that a complex trait evolved once instead of twice. If complex features are just as likely to appear on their own, then it is very hard to prove that two organisms share a common ancestor (Luskin 2017).

Accept Common Ancestry, Lose Convergence

What about the other side of the dilemma? If Kojonen accepts common ancestry, then what follows for his case for convergence and, by extension, his case for the “laws of form”? It seems like two results follow. First, he can no longer explain a lot of biological phenomena. This is because he says that convergence is “ubiquitous.” 

Second, in Kojonen’s model, convergence is part of his case for the laws of form. And these laws play a crucial role in the “fine-tuned” preconditions that help make evolution possible. Given that these preconditions arise from designed laws of nature, they play a vital part of Kojonen’s overall account of design. But if Kojonen accepts common ancestry (and its standard justification), then he loses a crucial element of his particular account of design. This greatly harms the heart of his model, which is to defend a certain view of design and its compatibility with evolutionary theory.

So Kojonen’s model has internal inconsistencies. He is basically stuck between a rock and a hard place. Kojonen’s understanding of (and justification for) “design” conflicts with both his own reasoning (about co-option and protein evolution) and the justification of common ancestry, which is a mainstay of evolution. So while Kojonen’s study of the laws of form is one of the most interesting ways he looks at design, this argument comes at a very high price.


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