"Darwin Devolves" Ch 1: The Pretense of Knowledge

Design

(Andy Walsh) #1

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 Ground

  • 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.


Darwin Devolves: The End of Evolution?
(George) #2

@AndyWalsh

I myself object to the discussion being described as Behe discussing “random variation”. And I’m sure Behe himself would object to that description.


(Andy Walsh) #3

Perhaps it wasn’t clear because I forgot to include a page number for that one (sorry), but that wording is a direct quote from the book (p 16).


#4

Thanks for posting Chapter 1. To me it was very boring. I really didn’t learn anything. I read popular science books to learn about a subject area that I don’t know much about or where I want to get the latest and greatest new findings explained to me by an expert in the field. Chapter 1 does neither. It is very non-informative.


(Robert Byers) #5

why should polar and brown bears show evolution? all it shows is segregated populations with different bodyplans. it doesn’t show how this happened. that genes are different would be expected.
then the wrong idea of reproductive compatibility is brougt up. nature or rather the mechanism for biological change that leads to new populations with different bodyplans from some original HAS NO INTEREST in whether there is/is not reproductive compatibility. tHats a human construction unknown to nature. all one needs to have had the mechanism take place and finish the job is a new bodyplan in a new population. thats why its accurate to say humans are divided into different species.
if species is real and everyone says it is. i am not sure or rather think its just segregated poulations maintaining a bodyplan unrelated to parents/cousins.


(George) #6

@AndyWalsh

It’s almost as if he put those “complaints” into the narrative as a sop to the nutty-er side of Creationism that is allergic to the word Evolution.

Those statements do not really seem congruent with the rest of Behe’s positions.


(George) #7

@Robert_Byers,

The mathematics for the speed in which mutations can drive a population towards a new body plan becomes a “driver” only when the average exchange of stabilizing genetic information reaches a LOW tipping point.

Until these exchanges reach this low ebb, body plans tend to be stable.

You need to at least understand Ring Species and how they work before you can start making conclusions about speciation in general.


(George) #8

@AndyWalsh

It’s almost as if he put those “complaints” into the narrative as a sop to the nutty-er side of Creationism that is allergic to the word Evolution,


#9

It will be interesting to see if Behe can explain how less fit alleles outcompete fitter alleles.

All of the mechanisms within the EES are natural and spontaneous, so I’m not sure what problem Behe is looking for. On top of that, EES is already a part of the modern theory, so it isn’t much of a debate. EES is little more than people trying to make their ideas look more original than they really are.

Build strawman in first chapter, spend rest of book beating it with a stick.


#10

Random genetic drift.


(John Mercer) #11

But to date, Behe has been obsessed with Darwinian evolution, which does not include drift. Drift is non-Darwinian.


#12

Random genetic drift only applies to neutral mutations, not deleterious mutations. If organisms with these supposed “devolved” mutations do just as well as those without the mutation, then how is it “devolution”?


(Arthur Hunt) #13

From pp. 16-17 of the excerpt:

But what precisely did the changes in polar bear APOB do to it compared to that of other mammals? When the same gene is mutated in humans and mice, studies show it frequently leads to high levels of cholesterol and heart disease. The scientists who studied the polar bear’s genome detected multiple mutations in APOB. Since few experiments can be done with grumpy polar bears, they analyzed the changes by computer. They determined that the mutations were very likely to be damaging - that is, likely to degrade or destroy the function of the protein the gene codes for.

From the paper I assume Behe is citing:

Substantial work has been done on the functional significance of APOB mutations in other mammals. In humans and mice, genetic APOB variants associated with increased levels of apoB are also associated with unusually high plasma concentrations of cholesterol and LDL, which in turn contribute to hypercholesterolemia and heart disease in humans (Benn, 2009; Hegele, 2009). In contrast with brown bear, which has no fixed APOB mutations compared to the giant panda genome, we find nine fixed missense mutations in the polar bear (Figure 5A). Five of the nine cluster within the N-terminal ba1 domain of the APOB gene, although the region comprises only 22% of the protein (binomial test p value = 0.029). This domain encodes the surface region and contains the majority of functional domains for lipid transport. We suggest that the shift to a diet consisting predominantly of fatty acids in polar bears induced adaptive changes in APOB, which enabled the species to cope with high fatty acid intake by contributing to the effective clearance of cholesterol from the blood.

This does not bode well for the rest of the book, IMO.


#14

Why you would even think this is just mind-boggling. I don’t know who “liked” your post, but they are as mistaken as you are. Since you are not likely to take my word for it I will step aside and let someone else explain it to you.


#15

This post warranted two likes? I’m incredulous. Are people simply confusing neutral evolution with genetic drift? I don’t know how else to explain what I am observing.


(John Harshman) #16

Let’s recall that your initial comment was pointless. What Behe was talking about was not genetic drift but his unrecognized failure to distinguish between reduction or loss of function and deleterious.

I presume you’re talking about nearly neutral evolution, which is indeed a thing. But you should try to be clear the first time, and if someone doesn’t understand, you should then explain further.


(Neil Rickert) #17

From what I have seen thus far, the book title should have been “Behe devolves”.


(John Mercer) #18

I wondered how long it would take to find Behe misrepresenting the evidence–and even worse, scientists’ clearly written interpretation of that evidence–but I didn’t think it would happen this quickly!

@bjmiller, you claimed on ENV that:
“For the first time, evolutionary claims can be properly tested, and Behe presents the most rigorous analysis to date based on hard data.”

Wow. The most rigorous. How did you measure the relative rigor of Behe’s analysis?

All studies demonstrated the same basic results.”

This study would obviously be part of all studies, whether Behe cited it or not. When you wrote that, were you referring to what this study actually demonstrated (gain of function), or Behe’s misrepresentation of what it demonstrated (“Laboratory experiments, field research, and theoretical studies all forcefully indicate that, as a result, random mutation and natural selection make evolution self-limiting.”)

Does Behe not understand the meaning of “missense”?

Why are you both so fond of using the adjective “all” so inappropriately?


(Timothy Horton) #19

Don’t attribute to deliberate misrepresentation that which can be explained by incompetence. :slightly_smiling_face: Although in this case it sure looks like Behe was engaged in some intentional non-truth. It wouldn’t be the first time either.


#20

No one is confused. Perhaps you are?