March 5, 2018.
Before we get to the details of evolution, it is important to start with a basic overview. It would be hard to truly evaluate the evidence without a proper understanding of the overall theory itself. Indeed, many have rejected the theory outright because they do not know what the theory actually says. Others misunderstand the theory, and thus reject it based on claims that the theory never makes. In this post we will go over a general overview of the theory of evolution by natural selection and attempt to hedge some misconceptions about evolution from the start.
What is the theory evolution?
When Charles Darwin published On the Origin of Species in 1859, he was not the first to suggest a theory of evolution. Actually, it wasn’t strictly evolution that he was proposing, but rather a theory that would describe the mechanism of evolution and a suggestion of the extent of evolution. The complete title of his work is On the Origin of Species by Means of Natural Selection. The thought of evolution was not original to Darwin; he was just the first to compile a large amount of biological evidence for it and propose a mechanism that might drive it. Like Copernicus and Galileo, Darwin’s theory was heavily opposed at first by the scientific community. However, as time went on and the evidence became clearer (and with the help of a few scientists that were readily convinced by Darwin’s theory and worked hard to defend it, such as Thomas Huxley), the scientific community eventually came around to the idea. Today, the vast majority of practicing biologist accept the theory of evolution to explain the diversity of life on the planet. The vast majority that are opposed (which is a tiny fraction of scientists, and usually scientists that are either in a different field or are not practicing) have an a priori reason for being opposed. However, especially in America, there is a strong anti-evolutionary current that runs through a large number of non-specialists and non-scientists. With the next few articles, I want to address the evolution issue and put forth the evidence for why the overwhelming majority of biologists have been convinced that the diversity of life on this planted is a product of evolution driven mainly (but not solely) by natural selection.
First things first, let’s start with something we all agree upon: everyone believes in evolution. You might say, “Wait, no I don’t… that’s what this whole series is about!” But I contend that you do. The concept of evolution is simply “decent with modification”, or more specifically the change in genes over time. I know the term ‘evolution’ carries some other baggage with it that we might not all agree upon, but I think we can all get behind the idea that our children are not genetically identical to us. Furthermore, even those who are opposed to evolution in the young-earth camp will concede that “microevolution” does indeed occur (as has been directly observed in the lab). We will see later that there really isn’t a difference between ‘micro’ and ‘macro’ evolution, but for now let’s assume that there is some kind of difference and that we all agree that microevolution occurs. So, what is so controversial about Darwin’s theory?
To answer this question, we need secondly to tackle the concept of natural selection. This is not a hard concept actually. According to the theory of natural selection, organisms that are better suited to an environment will be more likely to live to a reproductive age, and therefore likely to produce more offspring than those that are less well suited to the particular environment. Since an organism’s offspring generally holds many traits of the parents, those traits will become more prevalent in a population. There are varying degrees of selective pressure on different traits. For example, there might be a high selective pressure for an excellent sense of smell in dogs because if they can’t smell their prey, they will not eat and therefore will not survive. However, it could be said that the selective pressure for the sense of smell in fish is much lower because this sense is not very useful in catching prey in the ocean. Again, I don’t think this concept, in general, is all that controversial. We can easily conceptualize how it would work, and it makes intuitive sense that those organisms that are ‘more fit’ in a given environment will be more likely to survive and pass on their traits (or genes, as we now know what produces our traits) to the next generation.
The theory of evolution by natural selection says that it is this mechanism that has driven most, if not all, of the diversity of life. This is where the concept gets controversial. Darwin had amassed a large body of evidence to suggest that all life had evolved though the process explained above from a few, or perhaps a single, ancestor over millions (or billions) of years. His key insight of his day was his understanding of how truly large that number is. If you think about it, you probably can’t really conceptualize one million of anything, much less 100 million, or one billion. I know I can’t; this is precisely where the denial takes a firm hold. However, Darwin had the insight (which has now been mathematically validated) that this gradual change produced by natural selection multiplied over millions of years could account for the different species that currently populate the earth. But how could this be so?
One of the most common misconceptions of evolution is that evolution happens in a linear, ladder-like fashion, such as:
However, this is not what the theory of evolution claims. Evolution much more resembles a bush rather than a latter. Speciation in a population can happen for different reasons, but I think the easiest method to conceptualize is geographical isolation. Let’s say Species A is a certain finch species that lives on one of the Galapagos Islands. At first, the whole population of A is together on the island and looks very similar. There is some natural variation, but the population continues to interbreed. One day, a large gust of wind separates a small portion of Species A and blows them to an adjacent island that they would not have normally traveled to. This geographical isolation physically separates the two populations of Species A. The island that the small population was blown to has different sources of food than the first island, and therefore many of the small population cannot survive for very long because they can no longer eat the way they used to (for example, the nuts might be too hard to crack with their beaks). However, a few members of the population have very strong beaks due to natural variation in genes (caused by mutations) and are able to survive and reproduce. Over time, both populations of Species A continue to change in their physical traits based on the different environments of their respective islands. A few hundred to thousand years pass, and a small portion of the birds that got blown to the new island (or rather, descendants of these birds) happen to get blown back to the original island. However, by this time the two populations of birds have become so distinct that they no longer interbreed with one another. Thus, a speciation event has occurred and the populations on each island are two distinct species. We might call the population that originally got separated Species B and the original population either Species A or Species C, depending on how much evolution has taken place in the original population. We will say that the main population has sufficiently evolved to the point where they are considered a new species for simplicity sake. Thus, Species A is the common ancestor to Species B and Species C, as shown below:
Species B and C are closely related to each other (sometimes called ‘cousins’ or ‘sister’ groups) not because one of the species evolved from the other, but because they share a recent common ancestor, the original population of Species A.
Even at this point we aren’t in extremely controversial waters. Even young earth creationists will agree that speciation occurs. However, a new species of a bird is still a bird, right? This is where the problem of conceptualizing vast periods of time comes in. The theory of evolution by natural selection, however, says that all life on earth came about though many, many speciation events over millions of years from a common ancestral population. This is why evolution doesn’t really differentiate between ‘macro’ and ‘micro’ evolution- it’s all microevolution spread out over a very large amount of time. The ‘tree of life’ looks much more like a bush (for a good visualization of what this looks like, click here).
They theory of evolution has itself evolved over time, but the central logic and core elements that Darwin laid down in 1859 have held remarkably well over the past 150 years. Again it should be pointed out that Darwin was vigorously opposed by many scientists when he first published his theory. What is perhaps even more remarkable, however, is that Darwin put forth his theory without knowing many of the things we do today such as gene theory (that traits are passed on to the next generation through genes) and DNA. What has been said here might seem inconceivable to you at the moment. It was not my goal in this article to defend evolution, but rather to lay out the basic tenants of the theory. In the next article I plan on going over several lines of solid evidence that supports evolutionary theory to at least give a basis for why the biologist believe what they do. Then we will follow up with some of the common objections and answers to these objections. Before we get there, however, I want to clear up a few misconceptions from the start.
What the theory of evolution is not.
- Exactly what Charles Darwin said.
As I mentioned above, the theory of evolution has evolved with time, and our current understanding of evolution is not exactly identical to Darwin’s insights made in 1859. Though his core insights have held remarkably well, we now know that there are other mechanisms that drive evolution besides natural selection, though probably to a much lesser extent. Thus, attacking evolution by pointing out incorrect things that are written in The Origin of the Species is not a viable tactic to refute evolution. One must interact with the current understanding and discussion about evolution in the current scientific community.
- “Just a theory”
This has been clarified so many times I’m not quite sure why it still needs to be said, but it seems that it does. Many people reject evolution as “just a theory”. However, a scientific theory is much different than the popular use of the word in our language. A scientific theory is not a “guess” about the world. It is a model some aspect of our world, many times a mathematical model, that is well established and based on a body of facts/observations. To put it in perspective, gravity is a scientific theory, as is the germ theory of disease (that many diseases are caused by small organisms such as bacteria or viruses) and atomic theory (that all matter is made up of tiny particles called atoms). It’s here that we can get a clearer understanding between fact and theory. Gravity is both a fact and a theory- a fact (in so much as we can confidently say it is a fact, which still must always be open to correction if better data emerges) in that we observe and can measure the attraction between two bodies; and also a theory about how that works (mathematically). Thus, the late Stephen Jay Gould can say,
Well, evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world’s data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to explain them. Einstein’s theory of gravitation replaced Newton’s, but apples did not suspend themselves in mid-air, pending the outcome. And humans evolved from apelike ancestors whether they did so by Darwin’s proposed mechanism or by some other, yet to be discovered.
A well-established scientific theory is not a weak hypothesis that a few scientists hold. It is the groundwork upon which the work in the field is done. It is always possible that evolution by natural selection could be replaced by another theory that better explains the data (that is, the process(es) that drive evolution), but the data will still exist.
- A theory of purpose.
Contrary to what some philosophical naturalists think and what many young-earth creations claim that all “evolutionists” think, the theory of evolution is not a theory of purpose. It is a theory that seeks to explain the process by which the diversity of life (both past and present) evolved. It says nothing about purpose, or really anything beyond the data. It also doesn’t necessarily follow that we can apply the theory to any other discipline in science or any other aspect of life, as so many have. This application of evolutionary theory to other scientific disciplines is often (and rightly, in my opinion) hotly contested. But there need not be any teleology in the theory of evolution- that’s not something science, by definition, can determine. We must look else ware for a theory of purpose. You know where I believe that theory can be found.
- A theory of origins.
Strictly speaking, evolution is also not a theory of origins. It only describes the data we have, not how that data came to be. It does not say how life originated on this earth. Sure, there are scientists who are avidly working on that problem and looking for a solution (which I don’t know if we will ever be able to confidently assert, but I don’t think we need to place a ‘God of the gaps’ theory here either) but that is not what the theory of evolution describes. I say this only because some opponents of evolution attack the theory on the grounds that “life cannot come from non-life”. That debate aside, evolution never makes the claim that it can, and thus this the theory cannot be refuted on this premise.
- A theory in crisis.
If you have been in this discussion for very long, it is likely that you’ve heard a young-earth creationist at some point make the bold claim that evolution is a theory in crisis, or something along those lines to make you think that the scientists are about to throw the whole theory out. This is simply rhetoric, and it has no truth in it whatsoever. You don’t even have to agree with evolution to know that this statement is completely false. Todd Wood, a practicing biologist and young-earth creationist makes this point clear in one of his blogs:
Evolution is not a theory in crisis. It is not teetering on the verge of collapse. It has not failed as a scientific explanation. There is evidence for evolution, gobs and gobs of it. It is not just speculation or a faith choice or an assumption or a religion. It is a productive framework for lots of biological research, and it has amazing explanatory power. There is no conspiracy to hide the truth about the failure of evolution. There has really been no failure of evolution as a scientific theory. It works, and it works well.
He goes on to explain why he rejects the theory (which is not because it has major flaws that scientists simply ignore) based on his faith. I admire Dr. Wood for his honesty, and I fully believe that we can all believe what we want about the issue. The problem comes when false statements are made about the other side in effort to “debunk” it. Evolutionary theory has been established on the basis of much evidence and has powerful explanatory power. It is true that there is debate within the scientific community about evolutionary theory (and with any other active area of good science), but that discussion is not whether or not evolution happens, but rather how it happens- to what extent did each of the known mechanisms (and any unknown) play a role. I do not know of one practicing biologist without an a priori reason who rejects evolution. It is fundamental to modern biological science, such that evolutionary biologist (and communicant of the Greek Orthodox Church) Thodosius Dobzhansky wrote an article entitled “Nothing in Biology Makes Sense Except in the Light of Evolution.”
In my next post, I will attempt to lay out some (but certainly not all- that would be impossible) of the evidence as to why virtually all biologists accept the theory of evolution as a proven theory. I pray I haven’t upset too many of you already, though I fear I might have. That is not my intention. My intention is simply to bring some clarity to whatever sphere of influence I might have so that the discussions can be informed rather than using rhetoric that we have simply just heard from someone else. After the evidence is put forth, then we can have the discussions about the implications this has for our faith. As you know, I believe the two are not diametrically opposed, and I will explain my reasoning in the latter half of this series. I want to be clear that I am not saying “you must believe in evolution.” I believe the evidence is overwhelming on the side of evolution. What I am asking is that you are open to the possibility of evolution, but more importantly, open to other Christians holding that evolution was the way in which our Creator chose to bring forth the diversity of life that we see (at least so far as the evidence compels us currently). Too often has this been a divisive issue, and much too often have we lost our children because we gave them a false dichotomy. I pray you grant me some grace as we continue. If you have been with me this far, I ask you to stick with the through the end to hear my reasoning in full.
 For information found throughout this section see Coyne, J. Why evolution is true. (Penguin Group, 2010), Ferngren, G. Science and religion: a historical introduction. (The Johns Hopkins University Press, 2002), Collins, F. S. The language of God: A scientist presents evidence for belief. (Free Press, 2006), Prothero, D. Evolution: what the fossils say and why it matters. (Columbia University Press, 2007), and Rogers, A. The evidence for evolution. (The University of Chicago Press, 2011).
 The story goes that after Thomas Huxley heard Darwin’s theory, he exclaimed “Why didn’t I think of that?” See Wolpert, Lewis. The unnatural nature of science. Harvard University Press, 1994. p. 68.
 See Carroll, S. B. The making of the fittest: DNA and the ultimate forensic record of evolution. (WW Norton & Company, 2006), p. 41-67.
 I use this example because it is the famous (or infamous) example that is typically paired with Darwin’s original observations, though he gave much more evidence than just the Galapagos finches.
 Interbreeding is what typically defines a species, though this definition gets a little fuzzy when we start talking about organisms that do not reproduce sexually.
 See, for example, https://answersingenesis.org/natural-selection/speciation/speciation-yes-evolution-no/, https://creation.com/why-speciation-occurs, and http://www.icr.org/article/speciation-animals-ark/
 This is not to say that major genetic mutations cannot account for major changes in a single generation, as there are documented mechanisms to produce such a change such as gene duplication. For examples, fruit flies have been observed to grow an extra set of wings due to genetic mutations (see http://learn.genetics.utah.edu/content/basics/hoxgenes/). Speciation can also happen fairly rapidly if the conditions are right (such as a high selective pressure and small population size), and actually is what punctuated evolution predicts. See Jablonski, D. Approaches to Macroevolution: 1. General Concepts and Origin of Variation. Evol Biol 44, 427–450 (2017) for more information about mechanisms of macroevolution.
 I did use ‘evolution’ when describing the theory of evolution; see previous point.
 From http://toddcwood.blogspot.com/2009/09/truth-about-evolution.html, emp. his.
 See Dobzhansky, T. Nothing in biology makes sense except in the light of evolution. The American Biology Teacher 35, 125–129 (1973).