As I explained in a previous post, evolution is simply a change in the genetic makeup of a population, and natural selection is simply a mechanism that causes evolution. Everyone agrees that both evolution and natural selection occur. Even the most fervent and outspoken young earth creationism organizations acknowledge that natural selection is a real thing and causes the genetic makeup of populations to change. For example, everyone agrees that all dogs descended from a common ancestor, and creationists typically have no problems accepting that all of the species of Galapagos finches descended from a single species of finch that got blown out to the islands. So the disagreement between scientists and creationists is not about whether or not evolution occurs. Rather, it is about whether or not evolution has limits. You see, examples like dogs and finches are what creationists refer to as “microevolution,” which they define as small changes within a “kind” (the term “kind” is loosely defined, but they generally state that the scientific classification of “family” is roughly the same as a biblical “kind”). In contrast, they define “macroevolution” as large changes, such as those that would be required for a land mammal to evolve into a whale, and it is these large changes that they say are impossible. As I will demonstrate, however, this distinction is completely arbitrary, and it is neither logically nor scientifically valid.
First, it is important to realize that scientists do not generally accept the creationist definitions of these terms. The use of the terms is not completely standardized, but generally speaking, microevolution refers to either a change from one generation to the next, or a change within a species, whereas macroevolution is simply a large change caused by an accumulation of microevolutionary changes. This is a very important distinction. Creationists act as if micro and macroevolution are two totally separate processes, but in reality macroevolution is simply an accumulation of microevolutionary events. In other words, microevolution inevitably leads to macroevolution. So if microevolution happens, then, ipso facto, macroevolution also happens.
Let me illustrate it this way. Let’s talk about the evolution of land animals (i.e., the evolution of a strictly aquatic species into an amphibian that can live on land). Both creationists and scientists agree that this is an example of macroevolution. There are lots of changes that are necessary for this to take place, but the three biggest ones are:
- The development of limbs for locomotion.
- The ability to balance your body’s water content.
- The ability to breathe oxygen in the air.
There are species of fish alive today (such as mud skippers) which can come on land for short periods of time during low tide in order to forage. All three of the above criteria are more fully developed in them than in most fish. The ancestor of land animals was not a mud skipper, but the image of a mud skipper is useful for this example. So, let’s suppose that the great, great, great, etc. ancestor of land animals was an organism which, like the mud skipper, could come on land for brief periods of time to forage for food. For sake of example, let’s assign this first generation an average value of 1 for each of our three important traits. In other words, there is variation in the population, and some individuals have slightly more developed limbs (limbs = 1.2) and are slightly better at getting oxygen (breathing = 1.2) and regulating water (water balance = 1.2), whereas others are below average (0.8) for all of these traits, and most individuals are in the middle. Let’s further state, for sake of example, that you need a value of 100 for each trait in order to live on land (creationists would, therefore, state that achieving the value of 100 is impossible).
Now, in this first generation, the individuals that rank as 1.2 are going to be able to stay out of the water longer, which means that they have more time to hunt for food. This results in them getting more to eat, which causes them to produce more offspring than the less well developed individuals. As a result, the average value for the next generation will be 1.1. This is a simple example of natural selection causing evolution, and even ardent creationists would agree with me so far.
Now, in Generation 2 there will again be variation, and the individuals with the best limbs, best water balance, and best breathing will be able to forage more, causing them to produce more offspring, resulting in a mean value of 1.2 for Generation 3. This process will continue over and over again until eventually, at generation 1,000 they reach the threshold at which they can actually live on land (i.e., a mean value of 100). For sake of simplistic example, I obviously used artificial numbers, but this is more or less how evolution via natural selection actually occurs in real populations, and we can even use a series of mathematical formulas to calculate exactly how much change occurs from one generation to the next.
Hopefully, at this point, the problem with creationists’ distinction is clear. Creationists would agree with every single individual step of this process. They would agree that Generation 2 evolved from Generation 1, Generation 3 evolved from generation 2, etc. all the way up to Generation 1,000 evolving from Generation 999, but they would simultaneously claim that it is not possible that Generation 1,000 evolved from Generation 1. This is a clear violation of the Law of Transitive Properties. If you acknowledge that each microevolutionary step will occur, then you have just acknowledged that macroevolution will occur, because macroevolution is nothing more than the product of multiple steps of microevolution. So the creationist claim that “microevolution occurs but macroevolution is impossible” is logically inconsistent, and it is totally arbitrary without any scientific reasoning behind it (i.e., it is an ad hoc fallacy). Allow me to illustrate this process as a syllogism to make things more clear.
- Generation 2 evolved from Generation 1 (creationists agree)
- Generation 3 evolved from Generation 2 (creationists agree)
- Generation 1,000 evolved from Generation 999 (creationists agree)
- Therefore, Generation 1,000 evolved from Generation 1 (creationists disagree)
At this point, creationists like John Morris generally state that the problem with my explanation is that some of the steps would require mutations, and “no truly useful mutations have ever been observed.” It is true that you would need mutations to maintain variation and allow this process to happen, but it is completely and totally untrue that no useful mutations have ever been observed. There are numerous studies that have documented extremely beneficial mutations. So this is another great example of creationists not having the foggiest clue what they are talking about. Further, beneficial mutations would also be required for the evolution of some of the beak types found on Galapagos finches (which, remember, creationists have no problems accepting). So this argument is also a case of inconsistent reasoning. Finally, even IF the claim that “no beneficial mutations have been document” was true, it would be an argument from ignorance fallacy to conclude that, “therefore no beneficial mutations exist.”
Another attempt to discredit this argument is simply to state that macroevolution has never been observed. There are two problems with this argument. First, it is another argument from ignorance fallacy. The fact that we haven’t observed it doesn’t mean that it doesn’t occur. Second, of course we haven’t observed it. Large evolutionary changes take thousands, even millions of years to occur! So there is now way that it would even be possible for us to directly observe macroevolution. Therefore, the fact that we haven’t observed it cannot be used as evidence against macroevolution (note: please read this post before claiming that the fact that we haven’t directly observed macroevolution means that it isn’t science).
In summary, the creationist argument that “microevolution happens but macroevolution is impossible” is completely arbitrary, has no scientific support, is logically inconsistent, and violates the Law of Transitive Properties. Ergo, it must be rejected. With this arbitrary distinction now defeated, it is clear that accepting microevolution automatically means accepting macroevolution. Therefore, since creationists fully accept microevolution, they must also accept macroevolution.