I often observe that in discussions of evolution, both evolution skeptics and those who embrace neo-Darwinian evolution are prone to make one of two significant mistakes. Both stem from a failure to distinguish between microevolution and macroevolution.Let's see how Durston defines these terms.
The textbook for a genetics course I took at the University of Waterloo defined evolution as "changes in allele frequencies in a population over time." An allele can be described as a variation of a particular gene. Defining evolution in this way can be misleading; it would be more accurate to call this variation. No new genes are required, just variation in existing genes or the loss of existing genetic information. This sort of variation is typically referred to as microevolution.Random genetic drift and natural selection are the main mechanisms of evolution. Both of them reduce variation in a population because they eventually lead to fixation of one allele and the elimination of others. This is not misleading at all. The definition he quotes is the minimal definition of evolution because it results in a change in the heritable characteristics of a population.
Microevolution (variation) takes place through genetic drift, natural selection, mutations, insertions/deletions, gene transfer, and chromosomal crossover, all of which produce countless observed variations in plant or animal populations throughout history. Examples include variations of the peppered moth, Galápagos finch beaks, new strains of flu viruses, antibiotic-resistant bacteria, and variations in stickleback armour. Each year, thousands of papers are published dealing with examples of microevolution/variation.
Mutations cause variation. Mutations are not required for the minimal definition of evolution as long as the population contains variation. The reason why changes in allele frequencies are referred to as microevolution is because it really is evolution.
Kirk Durston is wrong to pretend that this is just "variation."
Mutations in the DNA sequence of an organism's genome will often result in new information. This has been demonstrated repeatedly. Some of the best examples are from Richard Lenski's long-term evolution experiment. For example, a series of five or six mutations has resulted in the creation of cells that can utilize citrate under conditions where the wild-type strain could not. The gene for uptake of citrate has been duplicated and brought under control of a new promoter and the entire complex has been duplicated again to produce extra copies of the enzyme. The activity of the enzyme produced by the new gene copies and their regulatory regions are ineffective in wild-type strains. Several other mutations in other genes are necessary for citrate uptake to work. The combination of all these mutations, rearrangements, and duplications results in new information that was not present in the parental strain.
Then there's the acquisition of antibiotic resistance by many strains of bacteria. That's microevolution and the fixation of new information in the genome.
The mistake I often hear evolution skeptics make is to the effect that "evolution" is all rubbish, bunk, and false. They are often astonished to learn that variation (which they completely agree with) is defined as "evolution." The solution is for evolution skeptics to be more precise on exactly what they have problems with. They can endorse microevolution (variation) but point out that a) it is misleading to call variation "evolution" and, b) their problems are with macroevolution.I'm glad to hear that Kirk Durston endorses microevolution and agrees with us that evolution is a fact. Let's hear what he thinks of macroevolution.
The definition of macroevolution is surprisingly non-precise for a scientific discipline. Macroevolution can be defined as evolution above the species level, or evolution on a "grand scale," or microevolution + 3.8 billion years. It has never been observed, but a theoretical example is the evolution from a chordate eel-like creature to a human being. Many people who embrace Darwinian evolution confidently state that evolution is a proven fact. They say this on the basis of thousands of papers discussing microevolution. Herein lies the second mistake ... the assumption that because variation/microevolution is such an overwhelmingly proven fact that, therefore, macroevolution must be as well.I have my own explanation of Macroevolution but Durston's description is good enough for now.
A good example of macroevolution is the evolution of modern humans and chimpanzees from a common ancestor that lived about five million years ago. This example has been well established by multiple lines of evidence including fossils, comparative morphology, and molecular data. It is a fact. It is as much of a fact as most things in science.
Kirk Durston thinks that macroevolution requires an increase in functional information but microevoluton does not.
So in order to clearly distinguish between microevolution and macroevolution in a rigorous scientific way, let me propose the following definitions:He thinks that macroevolution has never been demonstrated and he thinks that no new information can be fixed in a population by microevolution. He's wrong on both counts.
- Microevolution: genetic variation that requires no statistically significant increase in functional information.
- Macroevolution: genetic change that requires a statistically significant increase in functional information.
(Note: I do not mean to imply that Kirk Durston is guilty of ONLY two mistakes.)