Sunday, November 26, 2017

Review: The Blind Watchmaker by Richard Dawkins, part 1

I just finished reading The Blind Watchmaker by Richard Dawkins. Over all, I would say this is an excellent book. It wasn’t exactly what I expected, though. The subtitle reads, “Why the evidence of evolution reveals a universe without design.” I expected Dawkins to go into some detail about the hard evidence—fossils, geology, geography, genes, heredity, homology, etc. But really, most of the book was theoretical and speculative. For the most part, he showed how evolution could happen without showing that it did.

That’s not to say he didn’t discuss the hard evidence. He did. It just wasn’t the main focus of the book. Concerning the hard evidence, there was one part of the book I found to be especially compelling. It was chapter 10: “The one true tree of life.” More specifically, it was pages 270—276. And even more specifically, it was pages 274—275. I am probably going to butcher this explanation.

Okay, so there are a lot of genes in our DNA that code for proteins, and those same genes and proteins can be found in various species. However, there will be neutral differences, meaning there’ll be differences in the code that don’t affection the shape or function of the protein. That means they are invisible to natural selection. According to Dawkins, a given protein will change at the same rate regardless of what species that protein is found in. And, he says, we can know what that rate of change is, which allows us to know how long ago two species branched off from each other, i.e. how long ago their common ancestor lived. Unfortunately, Dawkins doesn’t tell us how we know about the mutation rate (unless it’s somewhere else in the book and I missed it).

Let’s suppose we have five different species, and we want to see how they are related to each other on a family tree. Well, we can look at the same protein in all five species, and by comparing them, we can tell how they are related to each other by how they differ. It’s a lot like textual criticism. You can tell that a text belongs to the Alexandrian text type or the Byzantine text type by looking at the differences of a given text. Supposedly, we can even tell how long ago each of them branched off from the others—the species, not the texts.

However, it’s always possible that a protein in two different species will change in the same way. It’s just a big coincidence when they do, and it apparently doesn’t happen very much. If it does happen, then looking at the one protein in each of the species will give you the wrong idea about how they are related and when their common ancestor lived.

But there’s a solution to that problem, and this is really the part that I found compelling. You don’t have to just rely on one protein to figure out a family tree. You can look at multiple proteins. The crazy thing is, when you look at multiple proteins, they will all tell the same story. You might get one that tells a slightly different story in case there was some huge coincidence in which the same protein in two different species mutated in exactly the same way. But that false reading can be recognized and corrected since every other protein tells the same story. It’s unlikely that one protein in two species would mutate in the same way, which is why we call it a coincidence, but it’s a whole lot more unlikely that two different proteins shared by two different species would both mutate in exactly the same way. These various proteins not only agree with each other in how the various species are related to each other, but they even agree on how long ago the different species branched off from each other.

I find this to be very compelling evidence for common ancestry. The fact that different species share the same protein, even if slightly modified, is flimsy evidence for a common ancestor. You could only arrive at that conclusion if you already assumed they had a common ancestor, and you were just trying to figure out how closely related they are. But if various species were not actually related by common ancestors, and you analyzed multiple proteins they had in common on the hypothesis that they were related, it seems highly unlikely to me that they would all give the same results. While you might dismiss one protein that points to a certain relationship, it’s hard to dismiss multiple proteins when they all give the same relationship and age of divergence.

It won’t do to say that a designer would, of course, use the same code in various species. Surely he would, but remember that we are talking about neutral differences in these proteins. They are differences that don’t affect the shape or function of the proteins. So there is no reason for them to be different on the hypothesis that a designer created them directly except that it doesn’t matter and they might as well be. But if it doesn’t matter, then we should expect the differences to be arbitrary, and if the differences are arbitrary, then we should not expect multiple proteins shared by different species to all agree on how those species would be related if they shared common ancestors.

That is not to say a designer is unlikely to have been involved. From what I understand, there are different theories in intelligent design about when, where, and how the designer got involved. Maybe he designed and assembled the first cell, and it took off from there. Maybe he interjects new information into DNA on rare occasions, like when he wants to add a brand new gene or disable one. Or maybe he manipulates the environment in such a way as to determine natural selection. All of those, it seems to me, would be consistent with the evidence I’ve been discussing. So a designer is not inconsistent with common descent. I only mean to say that Dawkins gave what seems to me to be a very compelling argument for common descent that suggests to me that each species was not a special creation that God made from scratch.

In part 2, I’ll talk about some problems I had with the book.

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