Does Evolution Explain Converging Ion Channels? Part 2
Recent studies of ion channels have dramatic implications for Christian apologetics. The fine-tuning, complexity, and convergence revealed in these remarkable structures support the superiority of intelligent design as an explanation for their origin.
In part 1 of this series, I discussed how shared ion channels in potatoes and mammalian brains exemplify molecular convergence. Such convergence supports the case for intelligent design better than it does the theory of evolution. Now in part 2, I will describe two more examples of how ion channels testify to a Creator’s handiwork.
While researching ion channels in spring of 2012, scientists at Washington University’s School of Medicine in St. Louis (WU) made a discovery that defies the long-held understanding that a protein’s structure alone determines its function.1 They discovered proteins involved in regulating electrical signals in nerve cells that lack any definable structure.
Proteins are made of amino acids and will take different shapes according to the sequence of their constituent amino acids.2 Different sequences will result in different shapes, and the shape of a protein determines its function.3 For years, scientists believed protein shape is the only factor deciding function.4 In fact, improperly shaped proteins were believed to be functionless—but this new discovery from WU adds yet another layer to the amazing complexity of proteins. It now appears that shape is not the sole determiner of protein function—indeed shape may not even be necessary in some cases.
At the time of their discovery, the WU research team was studying the physiological effects of BK (Big Potassium) channel behavior in the cells of mice5 in an attempt to gain more knowledge about the electrical signaling between cells, which allows them to communicate with one another. BK channels are large ion channels that allow the passage of potassium ions in and out of the cell.6 (Improperly functioning BK channels have been linked with epilepsy, asthma, and cardiovascular disease.7 Research in this area aims at a better understanding of ion channels in an effort to prevent these debilitating conditions.)
Ion channels, such as BK channels, send electrical signals to other cells in order to regulate nerve cells.8 At some point in the signaling process, these channels need to close in order to let the cells rest and “recharge.”9 The WU team observed BK channels as they opened and closed, and in doing so they found that an “intrinsically disordered” protein is responsible for the temporary shutdown of these channels.10 The proteins lack any definable structure yet they perform a highly specific function. In order to shut down signaling, the unstructured proteins must nestle into receptors inside BK channels.11 Without these proteins it would be impossible to close the channels. Christopher Lingle of WU explains,
It’s a two-step process, which distinguishes it from other inactivation mechanisms that have been described. My guess is that the part of the protein that binds to the potassium channel receptor may have to move through some very narrow spaces. It may be that by having a less defined structure, the protein can navigate more easily through tight spaces and get to the binding site.12
Such unstructured proteins make little sense from an evolutionary point of view. Chance mutations, the laws of chemical reactions and physics, and natural selection should make predictable biochemical systems—yet unstructured functioning proteins seem to fly in the face of what scientists know, or believe they know, about proteins. These unusual proteins will be more fully understood one day—and no doubt some will still postulate an evolutionary explanation for their origin.
However, will this explanation prove sufficient?
In summer 2012, scientists at the University of Vienna and the Woods Hole Oceanographic Institution gained new insights into the voltage-gated ion channels found in animals.13 Specifically, their research focused on ion channels in sea anemones and jellyfish. It was thought that the channels in the nervous systems of lower animals and their unicellular relatives were not capable of differentiating between calcium and sodium ions.14 On the other hand, the channels in higher animals are geared specifically for sodium ions, which are needed for the correct and efficient functioning of complex nervous systems.15
However, this study revealed that a particular group of basal animals with simple nervous systems does in fact possess ion channels with the ability to select for sodium. The voltage-gated sodium channels in these lower creatures differ from their counterparts in higher animals, yet perform the same function.
According to an evolutionary interpretation, these types of animals, belonging to a phylum called cnidarians, diverted from the rest of the animals more than 600 million years ago.16 This means that, supposing all animals came from a LUCA (Last Universal Common Ancestor), these similarly functioning sodium channels must have evolved twice within both higher and basal animals.17 Yet the data makes such a naturalistic conclusion highly unlikely.
Evaluating Explanatory Power
Biochemical systems are some of the most complicated systems on Earth. It is difficult for scientists to establish rules for how these systems ought to behave, especially because there is so much more to be learned about them. Embracing a theory that conflicts with the data increases the difficulty. Just as with the proposed evolutionary accounts for other biochemical systems, a naturalistic interpretation of ion channels will most likely involve astronomical improbabilities. It is becoming clearer that intelligent design presents a better explanation of the data.
In his book, Signature in the Cell, philosopher of science Stephen C. Meyer explains that historical scientists, such as evolutionary biologists, evaluate the explanatory power of competing explanations for the physical universe using a three-part criterion. Each historical explanation, or causal claim, needs:
- evidence that this cause was present;
- evidence that it can and has produced the effect in question; and
- evidence that there is a lack of proof for other possible causes.18
Meyer discusses the theory of evolution in light of these requirements. He writes, “Indeed, many scholars think that Charles Darwin structured his case in the Origin to show that natural selection met both the causal-adequacy and causal-existence conditions of a best explanation and, in so doing, that he was able to test his theory as well.”19
Yet at the time Darwin made his case for evolution he did not fully grasp the complexity and the fine-tuning of biochemical systems. As more research (particularly in evolutionary biology) is performed, evolution’s explanatory power decreases, and it is more challenging to view it as the best interpretation of the data. Intelligent design, however, seems to meet all three requirements for causal claims:
- God certainly was present at the time in question (creation of the universe);
- His creation of space-time is evidence enough that He is capable of also designing and creating today’s biochemical systems; and
- studies—such as those mentioned earlier—seemingly contradict the primary competing claim (Darwinian evolution).
Still, many people find the creation account in the book of Genesis almost, if not entirely, impossible to accept as true. But believing that the universe lacks a Creator sometimes necessitates accepting concepts more fantastic than those found in Genesis.
For example, as organisms evolved from simple to complex, and irreducibly complex nervous systems appeared, what change was made to determine that unstructured proteins no longer needed a distinct shape in order to perform a specific function, such as shutting down BK channels? Could the rules have been changed by chance? It makes better sense to recognize the existence of design in BK channels. Unguided processes must follow the strict rules of chance and evolution—but God’s designs are limited only by His imagination.
In considering the origin of the voltage-gated ion channels studied by the scientists at the University of Vienna and the Woods Hole Oceanographic Institution, evolution seems inadequate there as well. These channels are an example of functional molecular convergence (see part 1) in which biochemical systems are found to perform the same functions in unrelated organisms. This result is contrary to what is expected from an evolutionary standpoint. The idea that evolution—a random, mindless process—could independently repeat an outcome is difficult to accept.
Moreover, in order to ensure an organism’s survival, a simple nervous system would need to simultaneously evolve the ability to use sodium channels alongside the ability to differentiate between sodium and calcium ions. In higher animals the complex nervous system is obviously not the sole user of ion channels within organisms. Many other processes depend on calcium channels as well. Without channels that can differentiate between sodium and calcium ion signals, cellular damage can occur due to the wrongful activation of various signaling systems.20
Yet, if the mutation for the sodium channel occurred independently, cellular damage due to wrongful signaling from calcium ions would be extremely detrimental for the organism. If the mutation for differentiating between sodium and calcium ions occurred independently, then no real advantage would arise without the sodium channels themselves. In fact, a possible disadvantage would exist due to the extra energy being allocated to a signal differentiating process trying to select for sodium ion signals that do not exist within the system. This means natural selection would not necessarily “choose” animals of this kind to survive in order to evolve the sodium ion channels through further mutation.
How many more examples of findings contrary to the conclusions of evolution must be uncovered before naturalists consider an alternative approach?
Functional convergence coupled with the irreducible complexity of these ion channels and their proteins seems to fit better with a creation explanation. Just as a highly skilled human engineer would utilize proven designs, so it appears God reused the same concepts, designs, and functions in His many creations. As more and more ion channel discoveries come to light, God’s intentional design becomes more and more apparent. Ion channels are proving to resemble finely tuned and expertly designed systems. The complexity contained within these systems is making it increasingly, almost impossibly, difficult for evolutionary processes to provide an explanation for their origins. Ion channels seem to be loudly broadcasting the case for design.
1. Washington University School of Medicine, “Unusual Protein Helps Regulate Key Cell Communication Pathway,” ScienceDaily, April 22, 2012, http://www.sciencedaily.com/releases/2012/04/120423104956.htm.
2. Fazale Rana and Hugh Ross, Origins of Life (Colorado Springs: Navpress, 2004), 136.
4. Washington University School of Medicine, “Unusual Protein,” http://www.sciencedaily.com/releases/2012/04/120423104956.htm.
13. University of Vienna, “Ion Selectivity in Neuronal Signaling Channels Evolved Twice in Animals,” ScienceDaily, July 26, 2012, http://www.sciencedaily.com/releases/2012/07/120726135228.htm.
18. Stephen C. Meyer, Signature in the Cell (New York: HarperCollins, 2009), 168.
19. Ibid., 169.
20. University of Vienna, “Ion Selectivity,” http://www.sciencedaily.com/releases/2012/07/120726135228.htm.
By Kyle Keltz
Kyle Keltz received his BBA in finance from Texas Tech University in 2010, and is currently earning his MA in apologetics (concentration in scientific apologetics) from Southern Evangelical Seminary in Matthews, North Carolina.