Creation and Evolution (Part 17)

August 12, 2013     Time: 00:26:54

We were talking last time about the chances of amino acids coming together to form a single functioning protein molecule. I said that Steve Meyer in his book Signature in the Cell estimated this to be on the odds of one chance out of 1064 power – an absurdly small number even to get, not a living cell, but just a single functioning protein molecule. Well, the fellow that transcribes the Defenders podcasts looked up the reference and he said, “Bill, you got the figure wrong – you left something out. The actual figure is one out of 10164!” So I was only off by one hundred orders of magnitude! But this emphasizes just all the more how incredibly improbable the origin of life is on the basis of chance alone.

Evolution of Biological Complexity

Last time we talked about how life came to originate and I said that there would be nothing scientifically untoward in accepting Francis Crick’s statement that the origin of life on this planet was a miracle – that is to say, actually represented an intervention by God in the natural order of things to bring about biological life. But of course the existence of life alone is only the start of the process. What we now want to ask about is the evolution of biological complexity. We live in a fantastically complex biosphere of animals, plants, and other organisms and what we want to ask is how we, as Christians, ought to regard the evolution of biological complexity on our planet.

Distinguishing the Different Senses of “Evolution”

Part of the difficulty in assessing the contemporary evolutionary theory is that the word “evolution” is a sort of accordion word. That is to say, its meaning can be expanded or contracted depending on the context and so can mean different things in different contexts.

In his book Darwin’s Gift to Science and Religion,[1] the very prominent evolutionary biologist Francisco Ayala distinguishes three aspects of the contemporary evolutionary paradigm. The first is what he calls “evolution.” What is evolution according to this first definition? He says it is the process of change and diversification of living things over time; or, basically the idea that living organisms descended from previously living organisms with modifications – descent with modification. This is what biologists mean, Ayala says, when they say that evolution is a fact. He says when biologists say evolution is a fact they are simply referring to the process of change and diversification of living things over time. What are we to make of this? This definition of evolution is so broad as to be innocuous. Of course living things change and diversify over time. If this is all that biologists mean when they say that evolution is a fact then nobody would care to dispute them. Even the most conservative Young Earth Creationist will affirm evolution in this sense – that things change and diversify over time. But I think that Ayala probably means to imply more by this definition of evolution than simply the change and diversification of living things over time. I think that he probably takes it to imply what we can call the “Thesis of Common Ancestry,” or abbreviating it TCA.[2] This would be the view that all living things are descended from a single primordial ancestor. So any organisms, other than the very first, are descended from earlier organisms with changes. This is a far more significant claim. It would imply that there exists a sort of evolutionary tree of life, as it were, describing how things come to be and diversify. And this single evolutionary tree of life goes back to some single primordial ancestor. So the Thesis of Common Ancestry would deny that there is a multiplicity of such trees with a multiplicity of primordial ancestors. The Thesis of Common Ancestry would say there is simply a single evolutionary tree of life and that all living things are descended from some primordial ancestor. This thesis, I think, would demand significantly more evidence than the innocuous claim that things change and diversify over time.

The second part of the contemporary evolutionary paradigm that Ayala identifies is what he calls “evolutionary history.” This is the reconstruction of the universal tree of life showing how the various lineages branched off from each other over time. Notice that this second claim, evolutionary history, presupposes the Thesis of Common Ancestry. It presupposes that there is a universal tree of life rather than multiple evolutionary trees. Ayala explains that evolution in this second sense is a matter of great uncertainty. He says,

Unfortunately, there is a lot, lot, lot to be discovered still. To reconstruct evolutionary history, we have to know how the mechanisms operate in detail, and we have only the vaguest idea of how they operate at the genetic level, how genetic change relates to development and to function. . . . I am implying that what would be discovered would be not only details, but some major principles.[3]

Because he believes in the Thesis of Common Ancestry, Ayala accepts that there is a universal evolutionary tree but he recognizes that scientists have not been able to reconstruct it. One of the reasons that he gives for our inability to reconstruct evolutionary history is because of our failure to understand evolution in the third sense – namely, the mechanisms that drive evolutionary change. Let’s turn to that third aspect of the contemporary evolutionary paradigm which is the mechanisms of evolutionary change.

According to Professor Ayala, neither descent with modification (#1) nor evolutionary history (the Thesis of Common Ancestry) represents Charles Darwin’s unique contribution to evolutionary theory. Contrary to popular impression, evolutionary theories of life and the Thesis of Common Ancestry were widely proposed prior to Darwin and they were well known prior to Darwin’s theory. Rather, Darwin’s contribution, he says, lay in suggesting some explanatory mechanism for the evolutionary process; namely, natural selection operating on the random variations in living things. It is this mechanism that Darwin proposed to explain the adaptedness of organisms to their environment without the necessity of a designing intelligence. Ayala writes,

It was Darwin’s greatest accomplishment to show that the complex organization and functionality of living beings can be explained as the result of a natural process – natural selection – without any need to resort to a Creator or other external agents.[4]

With the development of modern genetics, genetic mutations have come to supplement Darwin’s proposed mechanism of natural selection by providing a means of achieving variation among living things.[5] Through mutations in living organisms variety arises on which natural selection can then operate. So, we could call this third point “Neo-Darwinism.” Neo-Darwinism will be the proposal that the mechanisms driving evolutionary development are natural selection and genetic mutation. Despite his profound admiration for Charles Darwin, it is evident from what I already said that Ayala thinks that we have only the vaguest understanding of the mechanisms driving evolutionary change. He writes,

The mechanisms accounting for these changes are still undergoing investigation[6] . . . The evolution of organisms is universally accepted by biological scientists, while the mechanisms of evolution are still actively investigated and are the subject of debate among scientists.[7]

I think you can therefore see how misleading it is when popular writers will assert that evolution is a proven fact which is universally accepted among biologists. That is true only in sense #1 – descent with modification or at most the Thesis of Common Ancestry. But evolution in the second and third senses of the word is not an accepted fact. According to Ayala,

The second and third issues – seeking to ascertain evolutionary history and to explain how and why evolution takes place – are matters of active scientific investigation. Some conclusions are well established. . . . Many matters are less certain, others are conjectural, and still others . . . remain largely unknown.[8]

So when we assess the contemporary evolutionary paradigm and ask whether or not it is true, I think we need to keep clearly in mind which aspect of that paradigm we are discussing. Otherwise, you can easily mislead people by switching the meanings of the word “evolution” in which case you are simply equivocating rather than talking about the same thing. When we assess this evolutionary paradigm, let’s make sure that we are clear on what aspect of that paradigm we are discussing. Otherwise, we are bound to lead to confusion and misunderstanding.


Question: I just wanted to ask if progress was inherent in this type of evolution.

Answer: No. Think of that first definition. The first definition simply says change and diversification. That wouldn’t necessarily imply progress. It wouldn’t necessarily imply increasing complexity. You could have a kind of devolution. In fact, when you think about it, you do see that in some animals. For example, salamanders that live in caves that have now lost sight and are blind because that isn’t needed in order to survive in such an environment. So I don’t think that progress is inherent in this. Though, again, this is where, in popular culture, evolution will often be taken to involve inherently the idea that things are getting better and better all the time rather than simply changing all the time. I think there you are introducing values – you are making value judgments – about different states and that requires something more than just the evolutionary process. You have to have some sort of transcendent basis of judgment and evaluation.[9]

Followup: Is “adaptability” a better word then?

Answer: It seems to me that adaptability would relate more closely to natural selection under the mechanisms. Organisms which undergo mutations that make them less adaptable to their environment will tend to be selected out. They will tend not to survive as well whereas a mutation that helps an organism to adapt better to its conditions would tend to be selected positively for survival.

Question: We sometimes hear microevolution and macroevolution and within species and evolving species. How does that relate to what you are talking about?

Answer: How does the terminology of macro and micro evolution relate? I’ve used that terminology myself in the past to describe limited evolutionary change such as you see, for example, in breeding roses or in breeding dogs. You see this kind of diversification and change taking place within limits. I’ve contrasted that with evolution as a sort of grand scenario describing evolutionary history. My understanding, however, is that is actually a misuse of terms and that we should not do that. Microevolution refers to evolution within species and anything above species evolution would be macroevolution. So while I think you need a sort of term to differentiate those two, apparently macro and micro isn’t the right terminology. But I think we can talk about things like the Thesis of Common Ancestry as indicating what we mean by, say, macroevolutionary change or something like it.

Question: I want to go back to step one. Is that accepted? Do we accept that because things like alike that they descended from each other. Is there any proof at all that there is a tree of life that one descended from another? I am reminded of Berra’s Blunder where he said that corvettes were descended from other vehicles. A common designer would have given similarity but not descent.

Answer: OK, you are getting a little ahead of ourselves. We will talk about the Thesis of Common Ancestry momentarily. You are referring to a very famous case by a fellow named Berra (not Yogi, but somebody else!) and among intelligent design or creationist circles Berra’s Blunder refers to this attempt on the part of this theorist to defend evolution by pointing to something like the evolution of the Ford Mustang over the years.[10] Remember how the Mustang, when it started off, was this tiny little car and then it got fancier and fancier over the years and he said this illustrates evolution. But clearly that doesn’t illustrate evolution at all! These later models didn’t evolve out of these earlier models; they were just built on similar design plans and the later automotive designers, rather than design the new model of the Mustang from the ground up, they would use a similar design model. So there was no common ancestry at all – on the contrary, what the illustration of the evolution of the Ford Mustang showed was quite the opposite; namely, that you could have similarity without ancestry. Having said that, however, certainly, I think we do have evidence within limited spheres of this kind of change and diversification that goes on over time. I mentioned, for example, the success that breeders have in breeding hybrid roses or dogs of different sorts or horses. So, the idea that organisms change and diversify over time, I think, is something that is widely accepted and that we can actually observe and bring about. Whether or not, though as I say, this means that the Thesis of Common Ancestry is true is a much more sweeping thesis that would require considerably more evidence than that. We will talk about that later.

Followup: So that is back to the micro and macro – we see lots and lots of evidence of modification within a kind but we don’t see horses turning into chimpanzees. We just don’t see it.[11]

Answer: Yes you are asking the same question about micro versus macro. What we will want to ask about is how sweeping is this sort of descent with modification and especially is it universal such as the Thesis of Common Ancestry holds. So those are the issues that we will want to talk about. And we will do so later.

Question: Regarding the evidence of descent with modification or similarities across species, there are things calls homologous genes. When you map out a genome of these nucleic acid sequences, you can find similarities – not just similarities but sweeping sequences of being identical. Once you find those genes, if you knock out a gene in, say, a rat and then you reinsert genetic material (what we call wild type genetic material that is not modified) from a human or a dog into that rat, you can actually rescue the affect of the knock out of that gene. So there is evidence that there is conservation of genetic sequences across things as diverse as a bird and a rat.

Answer: OK. We will talk about this in greater detail when we get to the Thesis of Common Ancestry but I think you have put your finger on what would be the most powerful evidence in favor of the Thesis of Common Ancestry and that is going to be the genetic evidence which is extremely interesting and would be the primary, I think, evidential grounds for affirming something like common ancestry. We will talk about that later.

Question: I might be getting a little ahead, but are you going to tie this at all to the fall?

Answer: I wasn’t. You are asking whether I am going to tie this into the fall of man and I take it this includes things like the historical Adam. I wasn’t going to. I was going to try to assess these theses and ask how we, as Christians, might have a sort of synoptic worldview that would take account of the findings of modern science but also take seriously the Bible. But I wasn’t going to say anything about the fall though this has certainly become a very hot topic lately.

Question: I am not sure if you’ve dealt with this before but are you going to speak at all about genetic bottlenecking? I know that there is research as far as when you go back you can trace when it looks like you had a lot of people and all of a sudden it looks like some kind of catastrophe happened and it bottlenecked into a certain small group and then expanded again.

Answer: This is related to the earlier question about the historical Adam because there have been claims recently that are being much discussed among Christian geneticists and other biologists as to whether or not the genetic evidence for human evolution is consistent with an original human pair or whether or not, as you put it, the population goes back to a bottleneck that gets no fewer than say a couple thousand people and then it broadens out again in which case the human population was never less than a few thousand at that bottleneck several tens of thousands of years ago. This is something that is currently being hotly debated. I did not intend to address that in this class.[12]

[Q&A: someone mentions a representative from Reasons to Believe is coming to Johnson Ferry church.]

Let’s look in more detail at these different aspects of the contemporary evolutionary paradigm. Since the second aspect – namely, evolutionary history – is simply the outworking of points #1 and #3, I am not going to address it specifically. I’d rather focus on theses #1 and #3 – in particular, the question of the Thesis of Common Ancestry and then the adequacies of the mechanisms of natural selection and random mutation. Next time we will take up the Thesis of Common Ancestry.[13]

[1] Francisco J. Ayala, Darwin’s Gift to Science and Religion, (Washington D.C.: Joseph Henry Press, 2007)

[2] 5:00

[3] As quoted by Larry A. Witham, Where Darwin Meets the Bible: Creationists and Evolutionists in America, (New York, NY: Oxford University Press, 2002), p. 90.

[4] Ayala, Darwin’s Gift, p. 47.

[5] 10:36

[6] Francisco J. Ayala, “The Evolution of Life: An Overview,” in Evolutionary and Molecular Biology: Scientific Perspectives on Divine Action, ed. Russell, Stoeger, and Ayala (Notre Dame, IN: University of Notre Dame Press, 1999), p. 22.

[7] Ibid., p. 21.

[8] Ayala, Darwin’s Gift, pp. 141-42.

[9] 15:13

[10] See Tim M. Berra, Evolution and the Myth of Creationism: A Basic Guide to the Facts in the Evolution Debate, (Stanford, CA: Stanford University Press, 1990), pp. 117-19. Note: Berra uses the Corvette, not Mustang, for his analogy.

[11] 20:29

[12] 24:57

[13] Total Running Time: 26:53 (Copyright © 2013 William Lane Craig)