The first chapter of Behe’s latest book is available online for promotional purposes. I thought it might help provide some specificity to the discussion around the book (e.g. Reviewing Behe’s “Darwin Devolves” ). Perhaps this belongs in that thread, but I didn’t want to disrupt conversations that have progressed in other directions.
I had a few thoughts to get the discussion going. Obviously the first chapter is not the whole book; still, as it is being used to promote the book I think it is fair to discuss on its own terms while not expecting it to answer every question.
- Common descent - On page 19, Behe directly acknowledges the strong evidence from multiple disciplines for the common descent of “organisms.” I appreciated this being handled so clearly and am curious if the significance will register with readers.
- Ursine common descent - The chapter opens with discussion of the shared ancestry of polar and brown bears, a “wonderful illustration of [Darwin]'s theory of evolution by random variation and natural selection.” I agree that it’s a good example to point to, including the interbreeding that illustrates the complexity of differentiating species.
- Biochemistry & molecular biology matter - As a student of molecular biology myself, I’m not going to quibble with the idea that evolution has to make sense at the level of molecules as well as the level of organisms.
- The “what” and “how” of evolution are distinct questions - Knowing the “what” (common descent) of evolution does not fully answer the mechanistic questions of “how.” And those mechanistic questions can proliferate in all sorts of interesting directions. They are not a single question with a single answer, and many of them are at best only partially answered.
- The incompleteness of Darwin’s theory - As you might gather from the title, Behe talks a lot about Darwin and Darwinism. From a history of science perspective, I think it is fair to point out that Darwin had an incomplete understanding of the mechanisms of inheritance, befitting of the broader state of biological knowledge of his era.
At least in this first chapter, I think there’s a lot of area on which I can agree with Behe.
Bits I’m Confused About (That are maybe clarified later or maybe I just didn’t get)
- The nature of function - In the polar bear/brown bear discussion, Behe claims that “65 to 83 percent of helpful, positively selected genes are estimated to have suffered at least one damaging mutation” (p 17, emphasis his) – that is, 65-83% of the 17 genes which differ between polar bears and brown bears and which show evidence at the sequence level of positive selection. But is that damaging in the sense of loss of function relative to the brown bear version, or in the sense of change of function? Because at the organism phenotype level, these mutations lead to phenotype changes with positive fitness benefits to the polar bear (such as change in fur color more appropriate to surroundings or change in metabolism to deal with a higher fat diet). In that sense, they are not damaging mutations at all. So in what sense is this a problem for even a strictly adaptationist understanding of evolution? Variations occurred at the molecular level which produced variations in phenotype at the organism level which led to increased fitness which resulted in those variations being selected for. How does Behe think the story should have gone instead?
- The information content of the word “evolved” - The chapter title refers to the idea that evolutionary biology is coasting on the success of answering “what” happened (common descent) to get unwarranted crediting for knowing “how” it happened. The first bit of evidence provided in support of this claim is the assertion that many sentences in biology texts and papers could be revised to drop the word ‘evolve’ without losing meaning. For example, he says “Humans have evolved a sense of self that is unparalleled in its complexity” has the same informational content as “Humans have a sense of self that is unparalleled in its complexity” (p 23) and so evolution is just getting a free ride in that sentence. But doesn’t it inform/remind us that humans descended from an ancestral population which did not possess such a sense of self? Isn’t that the “what” of evolution that he grants is well supported and is not disputing? Just because the word ‘evolved’ doesn’t tell us the mechanism–whether our human sense of self is the product of natural selection or something else–doesn’t mean it tells us nothing. So what is the objection to including ‘evolved’ in that sentence?
- What unites evolutionary biologists - The second bit of evidence for the pretense of knowledge is that evolutionary biologists present a united front to the public, while they are actually deeply divided. The division he cites is the extended evolutionary synthesis debate. But aren’t they united, with Behe, on the “what” of evolution while disagreeing on details of the “how”–at least in terms of relative importance? Is the concern here just that the broader public is not being told enough about the latest developments and debates in evolutionary biology, in terms of media coverage, pop sci books and introductory texts?
- Is nutrition harder? - The third bit of evidence for the pretense of knowledge is that we don’t know everything about human nutrition. I gather the reasoning is that nutrition can be studied in controlled circumstances with living subjects, and so is easier to study than the relative fitness of mutations in long-dead organisms. I can see a thread of truth there, within the context of many complicating factors. For example, many nutrition studies do not have as much control over the diet of participants as is implied. And more to the point, there are a wide range of strength of signals in both nutrition and evolutionary biology. We are very confident that lack of vitamin C will lead to scurvy, for example. So while some nutrition questions may be easier to answer than some evolutionary biology questions, it’s not clear that all nutrition questions are easier than all evolutionary biology questions or that all nutrition questions are so hard as to cause pessimism about evolutionary biology. (I also think Behe is conflating the difficulty of nutrition as a subject for scientific inquiry and the difficulty for the consumer of sifting through all extent nutrition claims.)
And even if we say yes, we will never be able to collect enough data to tease out the mechanism of how certain phenotypes evolved because the signal is too weak/ancient… so what? And doesn’t that cut both ways? The overall impression I got is that Behe will be presenting an alternative mechanism(s) to answer the “how” questions as the book goes on. But how will we know if the alternative is better if the questions are too hard to answer in the first place?
- Is the main point specifically about Darwin? As mentioned, Darwin features heavily in this chapter. The extended evolutionary synthesis debate is framed as pro-Darwin vs anti-Darwin for example. Major post-Darwin developments in evolutionary biology like neutral theory are mentioned in passing but largely just lumped together as “sundry alternatives to Darwin’s mechanism” (p 19). So is this book specifically a critique of Darwin’s mechanism, which is apparently strong adaptationism? Relatedly, if evolutionary biologists have come up with sundry alternatives to natural selection, how can they simultaneously be not looking for new ideas because everyone is patting their back, as suggested on p 22?
Wow. Apologies; that was more than I thought I would write when I started. If I had to summarize, I think Behe does a good job drawing a distinction between the “what” of evolution (common descent) and the “how” of evolution, acknowledges that a variety of mechanisms may play into the “how,” and then muddies things by using evolution generically in his critiques that apply at best only to strong adaptationism.