Ann Gauger has a 3-part series responding to Joshua Swamidass' review of the book Theistic Evolution: A Scientific, Philosophical, and Theological Critique:
- Answering Joshua Swamidass on Theistic Evolution: A Religious Agenda?
- Answering Joshua Swamidass on Theistic Evolution: What Do Theistic Evolutionists Believe?
- Answering Joshua Swamidass on Theistic Evolution: Sketchy Science, and a Swerve into Metaphysics
I don't agree with everything, but I still think the entire series is worth reading. Gauger lands several solid punches. Here are a few excerpts:
There are innumerable descriptions and definitions of theistic evolution. How things are phrased matters a lot. Some definitions are innocuous, like the view that God has caused change over time in living things, or even that God has caused “continuous and gradual biological change over time such that the history of life is best represented as a great branching tree pattern as Darwin argued.” (p. 41) But it comes down to this: If God guided or directed or intervened in the evolution of living things, can we tell? Did it produce any detectable effect? And assuming God used continuous and gradual biological change over time, did he guide, or did he not guide the process, and if he did guide it, is that detectable?
The issue for theistic evolutionists to address is thus not just guidance or no guidance. It’s also about the detectability of evolutionary change. Can we tell if design is real or illusory? Can it be seen, or detected, in living systems, or the cosmos?
These theistic evolutionists “allow for God’s action in origins, while doubting science’s ability to elucidate the details.” This is Swamidass’s definition. It’s pretty vague. To allow for God’s action means God could have guided or permitted or even intervened in our origins. But this puts us squarely in the neo-Thomist no man’s land, where guidance, direction, or intervention are assumptions of agency and thus are improper inferences. Did God do it without leaving any evidence that science could detect? That’s what theistic evolutionists must say, or they hold an intelligent design position.
But Swamidass himself says he is not a theistic evolutionist. To check his own account of his views I went to his website, Peaceful Science. He writes there: “I find confident faith in the scientific world, whether or not evolution is true.” This, I think, doesn’t mean he has faith in science, but rather he has faith in God that doesn’t depend on whether or not evolution is true. That’s an interesting way of phrasing it. His faith isn’t shaken by evolution. But it could also mean he has faith in science even if evolution should prove to be false. Josh, you might want to clarify. Then further down the page he says: “I see evolution as a reasonable (but incomplete) description of how God created us.” He has lots of other language about his faith in Jesus and his reasons for affirming faith and science. But in the end what he says is that there is good scientific reason to accept evolution as true, but also to acknowledge it as possibly incomplete. It might be that more than evolution is needed. This sounds like Francis Collins who concedes that evolution “might be guided.” It leaves the door open a crack. He doubts science is able to detect, demonstrate, or elucidate design. But he doesn’t rule it out.
That’s sufficiently vague to cover most of the bases. I wonder how many theistic evolutionist agree?
The only place Swamidass does engage the book’s scientific arguments is regarding the chapter on human genetics, “Evidence for Human Uniqueness.” (By way of disclosure, I was the primary author of this chapter.) Much of what he says needs some unpacking, so bear with me.
Swamidass begins with a challenge based on the neutral theory of molecular evolution. He sees this as profound evidence for common descent. The neutral theory claims that most evolutionary change is driven by genetic drift rather than positive selection. Genetic drift is a random process, where luck determines which mutations are preserved and which are lost. We usually speak of evolution “selecting for” beneficial mutations and “selecting against” harmful mutations. But in fact, selection is only one mechanism of evolutionary change, and most common mutations we find in genomes today are thought to be nearly neutral, neither good nor bad. They have become common or universal (fixed) in the population because every generation some mutations decrease and some increase in the population, for random reasons having nothing to do with whether they are beneficial or harmful. Some are lost entirely and some advance toward fixation. The net effect is an accumulation of mutations at a more or less steady rate. From this a number of interesting mathematical measures can be derived.
But Swamidass aims at nothing so sophisticated. He simply wants to point out that the longer two species have been separated the more different they are (assuming common descent). In his critique Swamidass says:
[T]here are ten times less differences between humans and chimpanzee genomes than there are between mice and rat genomes (e.g., see The Chimpanzee Sequencing and Analysis Consortium, “Initial Sequence of the Chimpanzee Genome and Comparison with the Human Genome,” Nature 437 [2005]: 69). Even with different measures, mice and rats are much more different than chimpanzees and humans. Why? Humans and chimpanzees mutate slower and diverged more recently. [Emphasis added.]This is actually a trivial statement, given the neutral theory. It can be formulated as
R x 2T = DR (mutation rate) x 2T (total divergence time) = D (genetic distance). One can use D and T to calculate R, or D and R to calculate T. But there’s a danger: you can’t use this relationship to “confirm” common descent, unless R, T, and D are determined independently of one another, because the equation depends on the assumption of common descent.
[...]
Although the above implies humans and chimpanzees diverged more recently than mouse and rat, within a framework of common ancestry, it does nothing to validate the framework itself. The former pair is simply more similar than the latter pair. To say the fact that rats and mice are 10 times more different genetically than we are from chimpanzees does not prove common descent nor does it disprove it. All it says is that mutations accumulate at a measurable rate, a rate that is by definition consistent with the proposed time of divergence. Swamidass likes the way the numbers work, saying they support common descent. If common descent is true, this steady accumulation of mutations is consistent with it. However, to justify the statement that common descent is true because the relationship D = 2T x R is true, he must demonstrate it is true independently of any methodological assumption of common descent.
But there is still a bridge to be crossed. The neutral theory is not sufficient to account for us as we are. Some mutations must have been guided to account for the differences between us and chimpanzees. Random neutrally accumulating mutations cannot generate in 6 million years the kinds of coordinated functional changes to anatomy, physiology, intellect, language ability, and sociality (among other things) that must be explained. These are things Swamidass does not address. I point out the kinds of changes that might be involved, namely changes in gene regulatory elements, splicing, RNA editing, non-coding regulation of chromosomal behavior, and more. But they would have to be guided, as my chapter discusses.
I have every hope that we will continue to learn more about how we differ from chimpanzees. It’s not all in the genome. One fact that should already astound us: as Josh says, “Humans and chimpanzees mutate slower and diverged more recently” than rats and mice, and so should be more similar to each other than rats and mice are. Instead, we differ a great deal more phenotypically than rats and mice do. We have language, abstract thought, music, art, physics, humor, ethics and morality, and religion. Chimpanzees don’t. Something big must have happened.
While we are talking about arguments for and against common descent, it’s good to remember that common descent cannot explain biology, even if it should prove to be historically true. It is not a mechanism of change, it is a statement of relatedness. Two organisms can be similar for a number of reasons.
First, if I grant that God providentially guides evolution (by whatever mechanism it happens), that does not mean science is silent about it. Swamidass is making a metaphysical move here. Several philosophical and theological theses have probably already been written about this kind of move. What Swamidass is doing is defining science as strictly limited to material and efficient causes. Science can make no inferences to immaterial causes by that definition. That is a move into philosophy. The chain of reasoning is continuous though: science provides the evidence, philosophy makes the inference as to cause, and theology indicates the nature of the cause. To say science is silent on God’s action is true if you mean science by itself. Yes, science is limited in that sense. But partnered with philosophy and theology, there is a great deal to be said.
Another metaphysical point: If God providentially guides evolution, that does not mean his guidance must be undetectable. The results of his guidance may be accessible to science. To say that they are not accessible is begging the question. That’s what the dispute is about — whether science can detect evidence of his guidance (with the above distinctions understood about the chain of reasoning involved).
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