#843 Random Mutations and Epigenetics

Dr. craig’s response

Not to worry, Vaughan! In my treatment of the Doctrine of Creation for my projected systematic philosophical theology I have a lengthy “Excursus on the Origin and Evolution of Life” in which I discuss the epigenetic factors that help to shape organismal evolution. In the contemporary Extended Evolutionary Synthesis, in contrast to the Modern Synthesis that preceded it, “important drivers of evolution, ones that cannot be reduced to genes, must be woven into the very fabric of evolutionary theory.”[1] The “gene-centric” focus of the Modern Synthesis fails to capture the full gamut of processes that direct evolution. “Missing pieces include how physical development influences the generation of variation (developmental bias); how the environment directly shapes organisms’ traits (plasticity); how organisms modify environments (niche construction); and how organisms transmit more than genes across generations (extragenetic inheritance).”[2] So you’re quite right to take notice of this significant change in evolutionary biology, and I’m grateful for your sharing this very interesting article with me.

Still, I don’t think you’ve understood the gist of my response to proponents of the Modern Synthesis, who claim that mutations occur randomly. Many Christians have thought that evolutionary theory is incompatible with Christian theism, since in the Christian view God is providentially supervising any mutations that occur, and therefore they are not occurring blindly or by sheer chance. My point was that when the proponents of the Modern Synthesis explained what they meant by “random,” it turns out that “random” mutations are not at all inconsistent with God’s directing mutations. What they say “random” means is that mutations do not occur for the benefit of the host organisms. That is to say, there is in the natural causes of mutations no directionality driving the process in favor of the flourishing of the host organism. Such a definition of “random” is obviously compatible with God’s directing and even causing mutations to occur. God-directed mutations need not imply some benefit for the host organism. Thus, mutations can be both directed by God and random in the sense defined.

The article you cite says nothing to contradict the definition of “random” that I quote from the proponents of the Modern Synthesis. Merely capitalizing the word “random” does not show that it is being differently defined. In fact, you should have capitalized the words, “with respect to their consequences.” That phrase reveals that the authors are not using “random” to mean “by pure chance,” but rather to indicate that the mutations are indifferent to the benefit conferred on their host organism. The point of their article is to show that in the particular plant they studied, mutations are, in fact, skewed or constrained by epigenetic factors to suppress deleterious mutations, so that the mutations tend toward the benefit of the plant in question.

The authors of the article report that they have discovered in the plant Arabidopsis thaliana a mutation bias associated with epigenetic factors that “acts to reduce levels of deleterious variation in Arabidopsis by decreasing mutation rate in constrained genes” (p. 104). They compare this bias to a pair of loaded dice: “The adaptive value of this bias can be conceptualized by the analogy of loaded dice with a reduced probability of rolling low numbers (that is, deleterious mutations), and thus a greater probability of rolling high numbers (that is, beneficial mutations)” (p. 105). Thus, in sharp contrast to claims of the Modern Synthesis, mutations may, indeed, be biased toward the benefit of the host organism in which they occur.

The evolutionary theorist James Shapiro has likewise argued in support of what he calls Natural Genetic Engineering (NGE), according to which organisms actively restructure their genomes in the course of evolution, using a set of bio-chemical and cellular NGE tools to rewrite their DNA.[3] He argues that organisms have a built-in S.O.S. system that can actually respond to stressors and dangers by generating mutations that will help to meet the challenge.

So if in the Extended Evolutionary Synthesis it turns out that mutations do, in fact, occur prejudicially for the benefit of the host organism, so much the better! That only reinforces my point that God can be directing the mutations that drive evolution forward. What we then have is a powerful form of argument I call an “Even if. . . ; but in fact. . . .” argument. Even if the mutations are random, they can be directed by God; but in fact, they are not random.